Develop Reference

java.lang.AssertionError at org.java_websocket.client.WebSocketClient.run(WebSocketClient.java:190)

I am using WebSocketClient class to get the data from websocket in my android app but when anything change in Internet connection ( Disconnect from Internet ) it gives the following error in WebSocketClient.java file
USER_COMMENT=null
ANDROID_VERSION=10
APP_VERSION_NAME=0.0.1
BRAND=google
PHONE_MODEL=Android SDK built for x86_64
CUSTOM_DATA=
STACK_TRACE=java.lang.AssertionError
at org.java_websocket.client.WebSocketClient.run(WebSocketClient.java:190)
at java.lang.Thread.run(Thread.java:919)
But the WebSocketClient.java is read only file it is coming from java-websocket-1.3.0.jar file
WebSocketClient.java
package org.java_websocket.client;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.URI;
import java.nio.ByteBuffer;
import java.nio.channels.ByteChannel;
import java.nio.channels.CancelledKeyException;
import java.nio.channels.ClosedByInterruptException;
import java.nio.channels.NotYetConnectedException;
import java.nio.channels.SelectionKey;
import java.nio.channels.SocketChannel;
import java.nio.channels.spi.SelectorProvider;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.CountDownLatch;
import org.java_websocket.SocketChannelIOHelper;
import org.java_websocket.WebSocket;
import org.java_websocket.WebSocketAdapter;
import org.java_websocket.WebSocketFactory;
import org.java_websocket.WebSocketImpl;
import org.java_websocket.WrappedByteChannel;
import org.java_websocket.WebSocket.READYSTATE;
import org.java_websocket.drafts.Draft;
import org.java_websocket.drafts.Draft_10;
import org.java_websocket.exceptions.InvalidHandshakeException;
import org.java_websocket.handshake.HandshakeImpl1Client;
import org.java_websocket.handshake.Handshakedata;
import org.java_websocket.handshake.ServerHandshake;
public abstract class WebSocketClient extends WebSocketAdapter implements Runnable {
protected URI uri;
private WebSocketImpl conn;
private SocketChannel channel;
private ByteChannel wrappedchannel;
private Thread writethread;
private Thread readthread;
private Draft draft;
private Map<String, String> headers;
private CountDownLatch connectLatch;
private CountDownLatch closeLatch;
private int timeout;
private WebSocketClient.WebSocketClientFactory wsfactory;
private InetSocketAddress proxyAddress;
public WebSocketClient(URI serverURI) {
this(serverURI, new Draft_10());
}
public WebSocketClient(URI serverUri, Draft draft) {
this(serverUri, draft, (Map)null, 0);
}
public WebSocketClient(URI serverUri, Draft draft, Map<String, String> headers, int connecttimeout) {
this.uri = null;
this.conn = null;
this.channel = null;
this.wrappedchannel = null;
this.connectLatch = new CountDownLatch(1);
this.closeLatch = new CountDownLatch(1);
this.timeout = 0;
this.wsfactory = new DefaultWebSocketClientFactory(this);
this.proxyAddress = null;
if (serverUri == null) {
throw new IllegalArgumentException();
} else if (draft == null) {
throw new IllegalArgumentException("null as draft is permitted for `WebSocketServer` only!");
} else {
this.uri = serverUri;
this.draft = draft;
this.headers = headers;
this.timeout = connecttimeout;
try {
this.channel = SelectorProvider.provider().openSocketChannel();
this.channel.configureBlocking(true);
} catch (IOException var6) {
this.channel = null;
this.onWebsocketError((WebSocket)null, var6);
}
if (this.channel == null) {
this.conn = (WebSocketImpl)this.wsfactory.createWebSocket(this, draft, (Socket)null);
this.conn.close(-1, "Failed to create or configure SocketChannel.");
} else {
this.conn = (WebSocketImpl)this.wsfactory.createWebSocket(this, draft, this.channel.socket());
}
}
}
public URI getURI() {
return this.uri;
}
public Draft getDraft() {
return this.draft;
}
public void connect() {
if (this.writethread != null) {
throw new IllegalStateException("WebSocketClient objects are not reuseable");
} else {
this.writethread = new Thread(this);
this.writethread.start();
}
}
public boolean connectBlocking() throws InterruptedException {
this.connect();
this.connectLatch.await();
return this.conn.isOpen();
}
public void close() {
if (this.writethread != null) {
this.conn.close(1000);
}
}
public void closeBlocking() throws InterruptedException {
this.close();
this.closeLatch.await();
}
public void send(String text) throws NotYetConnectedException {
this.conn.send(text);
}
public void send(byte[] data) throws NotYetConnectedException {
this.conn.send(data);
}
public void run() {
if (this.writethread == null) {
this.writethread = Thread.currentThread();
}
this.interruptableRun();
assert !this.channel.isOpen();
}
private final void interruptableRun() {
if (this.channel != null) {
try {
String host;
int port;
if (this.proxyAddress != null) {
host = this.proxyAddress.getHostName();
port = this.proxyAddress.getPort();
} else {
host = this.uri.getHost();
port = this.getPort();
}
this.channel.connect(new InetSocketAddress(host, port));
this.conn.channel = this.wrappedchannel = this.createProxyChannel(this.wsfactory.wrapChannel(this.channel, (SelectionKey)null, host, port));
this.timeout = 0;
this.sendHandshake();
this.readthread = new Thread(new WebSocketClient.WebsocketWriteThread());
this.readthread.start();
} catch (ClosedByInterruptException var3) {
this.onWebsocketError((WebSocket)null, var3);
return;
} catch (Exception var4) {
this.onWebsocketError(this.conn, var4);
this.conn.closeConnection(-1, var4.getMessage());
return;
}
ByteBuffer buff = ByteBuffer.allocate(WebSocketImpl.RCVBUF);
try {
while(this.channel.isOpen()) {
if (SocketChannelIOHelper.read(buff, this.conn, this.wrappedchannel)) {
this.conn.decode(buff);
} else {
this.conn.eot();
}
if (this.wrappedchannel instanceof WrappedByteChannel) {
WrappedByteChannel w = (WrappedByteChannel)this.wrappedchannel;
if (w.isNeedRead()) {
while(SocketChannelIOHelper.readMore(buff, this.conn, w)) {
this.conn.decode(buff);
}
this.conn.decode(buff);
}
}
}
} catch (CancelledKeyException var5) {
this.conn.eot();
} catch (IOException var6) {
this.conn.eot();
} catch (RuntimeException var7) {
this.onError(var7);
this.conn.closeConnection(1006, var7.getMessage());
}
}
}
private int getPort() {
int port = this.uri.getPort();
if (port == -1) {
String scheme = this.uri.getScheme();
if (scheme.equals("wss")) {
return 443;
} else if (scheme.equals("ws")) {
return 80;
} else {
throw new RuntimeException("unkonow scheme" + scheme);
}
} else {
return port;
}
}
private void sendHandshake() throws InvalidHandshakeException {
String part1 = this.uri.getPath();
String part2 = this.uri.getQuery();
String path;
if (part1 != null && part1.length() != 0) {
path = part1;
} else {
path = "/";
}
if (part2 != null) {
path = path + "?" + part2;
}
int port = this.getPort();
String host = this.uri.getHost() + (port != 80 ? ":" + port : "");
HandshakeImpl1Client handshake = new HandshakeImpl1Client();
handshake.setResourceDescriptor(path);
handshake.put("Host", host);
if (this.headers != null) {
Iterator i$ = this.headers.entrySet().iterator();
while(i$.hasNext()) {
Entry<String, String> kv = (Entry)i$.next();
handshake.put((String)kv.getKey(), (String)kv.getValue());
}
}
this.conn.startHandshake(handshake);
}
public READYSTATE getReadyState() {
return this.conn.getReadyState();
}
public final void onWebsocketMessage(WebSocket conn, String message) {
this.onMessage(message);
}
public final void onWebsocketMessage(WebSocket conn, ByteBuffer blob) {
this.onMessage(blob);
}
public final void onWebsocketOpen(WebSocket conn, Handshakedata handshake) {
this.connectLatch.countDown();
this.onOpen((ServerHandshake)handshake);
}
public final void onWebsocketClose(WebSocket conn, int code, String reason, boolean remote) {
this.connectLatch.countDown();
this.closeLatch.countDown();
if (this.readthread != null) {
this.readthread.interrupt();
}
this.onClose(code, reason, remote);
}
public final void onWebsocketError(WebSocket conn, Exception ex) {
this.onError(ex);
}
public final void onWriteDemand(WebSocket conn) {
}
public void onWebsocketCloseInitiated(WebSocket conn, int code, String reason) {
this.onCloseInitiated(code, reason);
}
public void onWebsocketClosing(WebSocket conn, int code, String reason, boolean remote) {
this.onClosing(code, reason, remote);
}
public void onCloseInitiated(int code, String reason) {
}
public void onClosing(int code, String reason, boolean remote) {
}
public WebSocket getConnection() {
return this.conn;
}
public final void setWebSocketFactory(WebSocketClient.WebSocketClientFactory wsf) {
this.wsfactory = wsf;
}
public final WebSocketFactory getWebSocketFactory() {
return this.wsfactory;
}
public InetSocketAddress getLocalSocketAddress(WebSocket conn) {
return this.channel != null ? (InetSocketAddress)this.channel.socket().getLocalSocketAddress() : null;
}
public InetSocketAddress getRemoteSocketAddress(WebSocket conn) {
return this.channel != null ? (InetSocketAddress)this.channel.socket().getLocalSocketAddress() : null;
}
public abstract void onOpen(ServerHandshake var1);
public abstract void onMessage(String var1);
public abstract void onClose(int var1, String var2, boolean var3);
public abstract void onError(Exception var1);
public void onMessage(ByteBuffer bytes) {
}
public ByteChannel createProxyChannel(ByteChannel towrap) {
return (ByteChannel)(this.proxyAddress != null ? new WebSocketClient.DefaultClientProxyChannel(towrap) : towrap);
}
public void setProxy(InetSocketAddress proxyaddress) {
this.proxyAddress = proxyaddress;
}
private class WebsocketWriteThread implements Runnable {
private WebsocketWriteThread() {
}
public void run() {
Thread.currentThread().setName("WebsocketWriteThread");
try {
while(!Thread.interrupted()) {
SocketChannelIOHelper.writeBlocking(WebSocketClient.this.conn, WebSocketClient.this.wrappedchannel);
}
} catch (IOException var2) {
WebSocketClient.this.conn.eot();
} catch (InterruptedException var3) {
}
}
}
public interface WebSocketClientFactory extends WebSocketFactory {
ByteChannel wrapChannel(SocketChannel var1, SelectionKey var2, String var3, int var4) throws IOException;
}
public class DefaultClientProxyChannel extends AbstractClientProxyChannel {
public DefaultClientProxyChannel(ByteChannel towrap) {
super(towrap);
}
public String buildHandShake() {
StringBuilder b = new StringBuilder();
String host = WebSocketClient.this.uri.getHost();
b.append("CONNECT ");
b.append(host);
b.append(":");
b.append(WebSocketClient.this.getPort());
b.append(" HTTP/1.1\n");
b.append("Host: ");
b.append(host);
b.append("\n");
return b.toString();
}
}
}

The third-party library has a description. You can write a class to inherit the WebSocketClient class and rewrite the code after network disconnection and reconnection. The code example of the third-party library is provided for reference.

How to create a Rollback log which generates automatically after each day using java.util.logging.Logger?

I am using the following code to create a custom log as per my requirements.
But unable to get the rollback feature as java.util.logging.Logger doesn't support it.
What are the possible options for me to implement?
Is it possible to generate rollback logs automatically using the same library?
Code :
private static class MyCustomFormatterforUpdate extends java.util.logging.Formatter {
#Override
public String format(LogRecord record) {
StringBuffer sb = new StringBuffer();
sb.append("update ApiStatistics set RespDateTime =");
sb.append(record.getMessage());
sb.append(";");
sb.append("\n");
return sb.toString();
}
}
java.util.logging.Logger updatefile = java.util.logging.Logger.getLogger("Update Script");
boolean appendu = false;
FileHandler fhu;
{
try {
fhu = new FileHandler("src/main/resources/updatescript.log",appendu);
updatefile.addHandler(fhu);
fhu.setFormatter(new MyCustomFormatterforUpdate());
} catch (IOException e) {
e.printStackTrace();
}
}

Building upon my previous answer you just need to build out the proxy implementation inferred in that answer. The idea is to install a proxy handler which allows you to open and close the FileHandler object. This enabled the rotation you need. Below is working example that will rotate when the date changes. The test case is included and the output will appear in the home folder by default.
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.util.Calendar;
import java.util.logging.ErrorManager;
import java.util.logging.FileHandler;
import java.util.logging.Filter;
import java.util.logging.Formatter;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogManager;
import java.util.logging.LogRecord;
import java.util.logging.SimpleFormatter;
import java.util.logging.XMLFormatter;
public class DailyFileHandler extends Handler {
public static void main(String[] args) throws IOException {
DailyFileHandler dfh = new DailyFileHandler();
try {
dfh.setFormatter(new SimpleFormatter());
LogRecord r1 = new LogRecord(Level.SEVERE, "test 1");
LogRecord r2 = new LogRecord(Level.SEVERE, "test 2");
r2.setMillis(r1.getMillis() + (24L * 60L * 60L * 1000L));
dfh.publish(r1);
dfh.publish(r2);
} finally {
dfh.close();
}
}
private Calendar current = Calendar.getInstance();
private FileHandler target;
public DailyFileHandler() throws IOException {
target = new FileHandler(pattern(), limit(), count(), false);
init();
}
public DailyFileHandler(String pattern, int limit, int count)
throws IOException {
target = new FileHandler(pattern, limit, count, false);
init();
}
private void init() {
super.setLevel(level());
super.setFormatter(formatter());
super.setFilter(filter());
try {
super.setEncoding(encoding());
} catch (UnsupportedEncodingException impossible) {
throw new AssertionError(impossible);
}
initTarget();
}
private void initTarget() {
target.setErrorManager(super.getErrorManager());
target.setLevel(super.getLevel());
target.setFormatter(super.getFormatter());
target.setFilter(super.getFilter());
try {
target.setEncoding(super.getEncoding());
} catch (UnsupportedEncodingException impossible) {
throw new AssertionError(impossible);
}
}
private void rotate() {
String pattern = pattern();
int count = count();
int limit = limit();
try {
super.setErrorManager(target.getErrorManager());
target.close();
FileHandler rotate = new FileHandler(pattern, 0, count, false);
rotate.setFormatter(new SimpleFormatter()); //empty tail.
rotate.close();
current = Calendar.getInstance();
target = new FileHandler(pattern, limit, count, true);
initTarget();
} catch (RuntimeException | IOException e) {
this.reportError("", e, ErrorManager.OPEN_FAILURE);
}
}
private boolean shouldRotate(long millis) {
Calendar cal = Calendar.getInstance();
cal.setTimeInMillis(millis);
return cal.get(Calendar.DAY_OF_YEAR) != current.get(Calendar.DAY_OF_YEAR);
}
#Override
public synchronized void publish(LogRecord record) {
if (shouldRotate(record.getMillis())) {
rotate();
}
target.publish(record);
}
#Override
public synchronized void close() throws SecurityException {
target.close();
}
#Override
public synchronized void setEncoding(String encoding) throws SecurityException, UnsupportedEncodingException {
target.setEncoding(encoding);
super.setEncoding(encoding);
}
#Override
public synchronized boolean isLoggable(LogRecord record) {
return target.isLoggable(record);
}
#Override
public synchronized void flush() {
target.flush();
}
#Override
public synchronized void setFormatter(Formatter newFormatter) {
target.setFormatter(newFormatter);
super.setFormatter(newFormatter);
}
#Override
public synchronized Formatter getFormatter() {
return target.getFormatter();
}
#Override
public synchronized String getEncoding() {
return target.getEncoding();
}
#Override
public synchronized void setFilter(Filter newFilter) throws SecurityException {
target.setFilter(newFilter);
super.setFilter(newFilter);
}
#Override
public synchronized Filter getFilter() {
return target.getFilter();
}
#Override
public synchronized void setErrorManager(ErrorManager em) {
target.setErrorManager(em);
super.setErrorManager(em);
}
#Override
public synchronized ErrorManager getErrorManager() {
return target.getErrorManager();
}
#Override
public synchronized void setLevel(Level newLevel) throws SecurityException {
target.setLevel(newLevel);
super.setLevel(newLevel);
}
#Override
public synchronized Level getLevel() {
return target.getLevel();
}
private String pattern() {
LogManager m = LogManager.getLogManager();
String p = getClass().getName();
String pattern = m.getProperty(p + ".pattern");
if (pattern == null) {
pattern = "%h/java%u.log";
}
return pattern;
}
private int limit() {
LogManager m = LogManager.getLogManager();
String p = getClass().getName();
String v = m.getProperty(p + ".limit");
int limit = v == null ? Integer.MAX_VALUE : Integer.parseInt(v);
return limit;
}
private int count() {
LogManager m = LogManager.getLogManager();
String p = getClass().getName();
String v = m.getProperty(p + ".count");
int limit = v == null ? 7 : Integer.parseInt(v);
return limit;
}
private Level level() {
LogManager m = LogManager.getLogManager();
String p = getClass().getName();
String v = m.getProperty(p + ".level");
if (v != null) {
try {
return Level.parse(v);
} catch (Exception e) {
this.reportError(v, e, ErrorManager.OPEN_FAILURE);
}
}
return Level.ALL;
}
private Formatter formatter() {
LogManager m = LogManager.getLogManager();
String p = getClass().getName();
String v = m.getProperty(p + ".formatter");
if (v != null) {
try {
return Formatter.class.cast(Class.forName(v).newInstance());
} catch (Exception e) {
this.reportError("", e, ErrorManager.OPEN_FAILURE);
}
}
return new XMLFormatter();
}
private Filter filter() {
LogManager m = LogManager.getLogManager();
String p = getClass().getName();
String v = m.getProperty(p + ".filter");
if (v != null) {
try {
return Filter.class.cast(Class.forName(v).newInstance());
} catch (Exception e) {
this.reportError("", e, ErrorManager.OPEN_FAILURE);
}
}
return null;
}
private String encoding() {
LogManager m = LogManager.getLogManager();
String p = getClass().getName();
String v = m.getProperty(p + ".encoding");
if (v != null) {
try {
return Charset.forName(v).name();
} catch (Exception e) {
this.reportError(v, e, ErrorManager.OPEN_FAILURE);
}
}
return null;
}
}

A suggestion would be please use other logging frameworks which has many features in them
instead of java.util.logging.Logger
Useful links
configure-log4j-for-creating-daily-rolling-log-files
log4j-formatting-examples
a-guide-to-logging-in-java

How to add second activity in Amazon SWF hello_sample example

I've successfully implemented the simple Java Amazon SWF example called hello_sample. I created the ActivityWorker executable that polls SWF for activity tasks to process. I created the WorkflowWorker executable that polls SWF for decision tasks and I have a WorkflowStarter executable that kicks off the workflow execution. It works as advertised. What I don't understand is how do I configure and add a second activity to run after the first activity?
WorkflowWorker:
public class WorkflowWorker {
private static final AmazonSimpleWorkflow swf = AmazonSimpleWorkflowClientBuilder.defaultClient();
public static void main(String[] args) {
PollForDecisionTaskRequest task_request =
new PollForDecisionTaskRequest()
.withDomain(Constants.DOMAIN)
.withTaskList(new TaskList().withName(Constants.TASKLIST));
while (true) {
System.out.println(
"WorkflowWorker is polling for a decision task from the tasklist '" +
Constants.TASKLIST + "' in the domain '" +
Constants.DOMAIN + "'.");
DecisionTask task = swf.pollForDecisionTask(task_request);
String taskToken = task.getTaskToken();
if (taskToken != null) {
try {
executeDecisionTask(taskToken, task.getEvents());
}
catch (Throwable th) {
th.printStackTrace();
}
}
}
}
private static void executeDecisionTask(String taskToken, List<HistoryEvent> events) throws Throwable {
List<Decision> decisions = new ArrayList<Decision>();
String workflow_input = null;
int scheduled_activities = 0;
int open_activities = 0;
boolean activity_completed = false;
String result = null;
System.out.println("WorkflowWorker is executing the decision task for the history events: [");
for (HistoryEvent event : events) {
System.out.println(" " + event);
switch(event.getEventType()) {
case "WorkflowExecutionStarted":
workflow_input = event.getWorkflowExecutionStartedEventAttributes().getInput();
break;
case "ActivityTaskScheduled":
scheduled_activities++;
break;
case "ScheduleActivityTaskFailed":
scheduled_activities--;
break;
case "ActivityTaskStarted":
scheduled_activities--;
open_activities++;
break;
case "ActivityTaskCompleted":
open_activities--;
activity_completed = true;
result = event.getActivityTaskCompletedEventAttributes().getResult();
break;
case "ActivityTaskFailed":
open_activities--;
break;
case "ActivityTaskTimedOut":
open_activities--;
break;
}
}
System.out.println("]");
if (activity_completed) {
decisions.add(
new Decision()
.withDecisionType(DecisionType.CompleteWorkflowExecution)
.withCompleteWorkflowExecutionDecisionAttributes(
new CompleteWorkflowExecutionDecisionAttributes()
.withResult(result)));
}
else {
if (open_activities == 0 && scheduled_activities == 0) {
ScheduleActivityTaskDecisionAttributes attrs =
new ScheduleActivityTaskDecisionAttributes()
.withActivityType(new ActivityType()
.withName(Constants.ACTIVITY)
.withVersion(Constants.ACTIVITY_VERSION))
.withActivityId(UUID.randomUUID().toString())
.withInput(workflow_input);
decisions.add(
new Decision()
.withDecisionType(DecisionType.ScheduleActivityTask)
.withScheduleActivityTaskDecisionAttributes(attrs));
}
else {
// an instance of HelloActivity is already scheduled or running. Do nothing, another
// task will be scheduled once the activity completes, fails or times out
}
}
System.out.println("WorkflowWorker is exiting the decision task with the decisions " + decisions);
swf.respondDecisionTaskCompleted(
new RespondDecisionTaskCompletedRequest()
.withTaskToken(taskToken)
.withDecisions(decisions));
}
}
ActivityWorker:
public class ActivityWorker {
private static final AmazonSimpleWorkflow swf = AmazonSimpleWorkflowClientBuilder.defaultClient();
private static CountDownLatch waitForTermination = new CountDownLatch(1);
private static volatile boolean terminate = false;
private static String executeActivityTask(String g_species) throws Throwable {
String s = " ******** Hello, " + g_species + "!";
System.out.println(s);
String cwd = Paths.get(".").toAbsolutePath().normalize().toString();
String filename = "g_species.txt";
Path filePath = Paths.get(cwd, filename);
String filePathName = filePath.toString();
BufferedWriter output = null;
try {
File file = new File (filePathName);
output = new BufferedWriter(new FileWriter(file));
output.write(g_species);
}
catch (IOException e) {
e.printStackTrace();
}
finally {
if (output != null) {
output.close();
}
}
return g_species;
}
public static void main(String[] args) {
Runtime.getRuntime().addShutdownHook(new Thread() {
#Override
public void run() {
try {
terminate = true;
System.out.println("ActivityWorker is waiting for the current poll request to return before shutting down.");
waitForTermination.await(60, TimeUnit.SECONDS);
}
catch (InterruptedException e) {
// ignore
System.out.println(e.getMessage());
}
}
});
try {
pollAndExecute();
}
finally {
waitForTermination.countDown();
}
}
public static void pollAndExecute() {
while (!terminate) {
System.out.println("ActivityWorker is polling for an activity task from the tasklist '"
+ Constants.TASKLIST + "' in the domain '" + Constants.DOMAIN + "'.");
ActivityTask task = swf.pollForActivityTask(new PollForActivityTaskRequest()
.withDomain(Constants.DOMAIN)
.withTaskList(new TaskList().withName(Constants.TASKLIST)));
String taskToken = task.getTaskToken();
if (taskToken != null) {
String result = null;
Throwable error = null;
try {
System.out.println("ActivityWorker is executing the activity task with input '" + task.getInput() + "'.");
result = executeActivityTask(task.getInput());
}
catch (Throwable th) {
error = th;
}
if (error == null) {
System.out.println("The activity task succeeded with result '" + result + "'.");
swf.respondActivityTaskCompleted(
new RespondActivityTaskCompletedRequest()
.withTaskToken(taskToken)
.withResult(result));
}
else {
System.out.println("The activity task failed with the error '"
+ error.getClass().getSimpleName() + "'.");
swf.respondActivityTaskFailed(
new RespondActivityTaskFailedRequest()
.withTaskToken(taskToken)
.withReason(error.getClass().getSimpleName())
.withDetails(error.getMessage()));
}
}
}
}
}
WorkflowStarter that kicks it all off:
public class WorkflowStarter {
private static final AmazonSimpleWorkflow swf = AmazonSimpleWorkflowClientBuilder.defaultClient();
public static final String WORKFLOW_EXECUTION = "HelloWorldWorkflowExecution";
public static void main(String[] args) {
String workflow_input = "Amazon SWF";
if (args.length > 0) {
workflow_input = args[0];
}
System.out.println("Starting the workflow execution '" + WORKFLOW_EXECUTION +
"' with input '" + workflow_input + "'.");
WorkflowType wf_type = new WorkflowType()
.withName(Constants.WORKFLOW)
.withVersion(Constants.WORKFLOW_VERSION);
Run run = swf.startWorkflowExecution(new StartWorkflowExecutionRequest()
.withDomain(Constants.DOMAIN)
.withWorkflowType(wf_type)
.withWorkflowId(WORKFLOW_EXECUTION)
.withInput(workflow_input)
.withExecutionStartToCloseTimeout("90"));
System.out.println("Workflow execution started with the run id '" +
run.getRunId() + "'.");
}
}

I would recommend to not reinvent the wheel and use the AWS Flow Framework for Java that is officially supported by Amazon. It already implements all the low level details and allows you to focus on a business logic of your workflow directly.
Here is an example worklow that uses three activities (taken from the developer guide).
Activities interface:
import com.amazonaws.services.simpleworkflow.flow.annotations.Activities;
import com.amazonaws.services.simpleworkflow.flow.annotations.ActivityRegistrationOptions;
#ActivityRegistrationOptions(defaultTaskScheduleToStartTimeoutSeconds = 300,
defaultTaskStartToCloseTimeoutSeconds = 10)
#Activities(version="1.0")
public interface GreeterActivities {
public String getName();
public String getGreeting(String name);
public void say(String what);
}
Activities implementation:
public class GreeterActivitiesImpl implements GreeterActivities {
#Override
public String getName() {
return "World";
}
#Override
public String getGreeting(String name) {
return "Hello " + name;
}
#Override
public void say(String what) {
System.out.println(what);
}
}
Workflow interface:
import com.amazonaws.services.simpleworkflow.flow.annotations.Execute;
import com.amazonaws.services.simpleworkflow.flow.annotations.Workflow;
import com.amazonaws.services.simpleworkflow.flow.annotations.WorkflowRegistrationOptions;
#Workflow
#WorkflowRegistrationOptions(defaultExecutionStartToCloseTimeoutSeconds = 3600)
public interface GreeterWorkflow {
#Execute(version = "1.0")
public void greet();
}
Workflow implementation:
import com.amazonaws.services.simpleworkflow.flow.core.Promise;
public class GreeterWorkflowImpl implements GreeterWorkflow {
private GreeterActivitiesClient operations = new GreeterActivitiesClientImpl();
public void greet() {
Promise<String> name = operations.getName();
Promise<String> greeting = operations.getGreeting(name);
operations.say(greeting);
}
}
The worker that hosts both of them. Obviously it can be broken into separate activity and workflow workers:
import com.amazonaws.ClientConfiguration;
import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.services.simpleworkflow.AmazonSimpleWorkflow;
import com.amazonaws.services.simpleworkflow.AmazonSimpleWorkflowClient;
import com.amazonaws.services.simpleworkflow.flow.ActivityWorker;
import com.amazonaws.services.simpleworkflow.flow.WorkflowWorker;
public class GreeterWorker {
public static void main(String[] args) throws Exception {
ClientConfiguration config = new ClientConfiguration().withSocketTimeout(70*1000);
String swfAccessId = System.getenv("AWS_ACCESS_KEY_ID");
String swfSecretKey = System.getenv("AWS_SECRET_KEY");
AWSCredentials awsCredentials = new BasicAWSCredentials(swfAccessId, swfSecretKey);
AmazonSimpleWorkflow service = new AmazonSimpleWorkflowClient(awsCredentials, config);
service.setEndpoint("https://swf.us-east-1.amazonaws.com");
String domain = "helloWorldWalkthrough";
String taskListToPoll = "HelloWorldList";
ActivityWorker aw = new ActivityWorker(service, domain, taskListToPoll);
aw.addActivitiesImplementation(new GreeterActivitiesImpl());
aw.start();
WorkflowWorker wfw = new WorkflowWorker(service, domain, taskListToPoll);
wfw.addWorkflowImplementationType(GreeterWorkflowImpl.class);
wfw.start();
}
}
The workflow starter:
import com.amazonaws.ClientConfiguration;
import com.amazonaws.auth.AWSCredentials;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.services.simpleworkflow.AmazonSimpleWorkflow;
import com.amazonaws.services.simpleworkflow.AmazonSimpleWorkflowClient;
public class GreeterMain {
public static void main(String[] args) throws Exception {
ClientConfiguration config = new ClientConfiguration().withSocketTimeout(70*1000);
String swfAccessId = System.getenv("AWS_ACCESS_KEY_ID");
String swfSecretKey = System.getenv("AWS_SECRET_KEY");
AWSCredentials awsCredentials = new BasicAWSCredentials(swfAccessId, swfSecretKey);
AmazonSimpleWorkflow service = new AmazonSimpleWorkflowClient(awsCredentials, config);
service.setEndpoint("https://swf.us-east-1.amazonaws.com");
String domain = "helloWorldWalkthrough";
GreeterWorkflowClientExternalFactory factory = new GreeterWorkflowClientExternalFactoryImpl(service, domain);
GreeterWorkflowClientExternal greeter = factory.getClient("someID");
greeter.greet();
}
}

Design Pattern Command for Switch java

I want to use design pattern for this switch - case code.
I tried to use the command pattern, but I could not understand how(I was programming only 2 for months)
I wrote this program to learn how to better program.
My code:
public class Server {
private static final String READ_NEW_MESSAGES = "read new mes";
private static final String SEND_PRIVATE_MESSAGES = "send mes";
private static final String JOIN_CHAT = "find chat";
private static final String CREATE_CHAT = "chating";
private static final String QUIT = "quit";
private static final String EXIT = "exit";
private static final String REGISTRATION = "reg";
private static final String CREATE_PRIVATE_CHAT = "priv chat";
private static final String CONNECT_TO_PRIVATE_CHAT = "connect pm";
private static final String START_CHAT = "Start";
private Populator<PrivateMessage> privateMessagePopulator;
private Populator<Registration> registrationPopulator;
private Populator<Message> messagePopulator;
private Populator<PrivateChat> privateChatPopulator;
private Populator<Chat> publicChatPopulator;
private List<PrivateMessage> privateMessages;
private BufferedReader reader;
private String currentUser;
private Set<String> users;
private static Logger log = Logger.getLogger(Server.class.getName());
private List<Chat> chats;
private String password;
private Set<Registration> registration;
private List<PrivateChat> pmChat;
private String chatName;
public Server() {
server();
}
public void server() {
reader = new BufferedReader(new InputStreamReader(System.in));
privateMessages = new ArrayList<PrivateMessage>();
users = new HashSet<String>();
chats = new ArrayList<Chat>();
privateMessagePopulator = new PrivateMessagePopulator();
privateChatPopulator = new PrivateChatPopulator();
publicChatPopulator = new PublicChatPopulator();
messagePopulator = new MessagePopulator();
registrationPopulator = new RegistratorPopulator();
registration = new HashSet<Registration>();
pmChat = new ArrayList<PrivateChat>();
}
public void start() {
String decition = "";
while (true) {
try {
registrationOrLogin();
} catch (IOException e1) {
e1.printStackTrace();
}
while (decition != QUIT) {
System.out.println("Create a chat - chating");
System.out.println("Join the chat - find chat");
System.out.println("Send private message - send mes");
System.out.println("Read new messages - new mes");
System.out.println("Quit - quit");
System.out.println("Create private chat - priv chat");
System.out.println("Connect to private chat - connect pm");
try {
decition = reader.readLine();
switch (decition) {
case CREATE_PRIVATE_CHAT:
createPrivateChat();
break;
case CREATE_CHAT:
createChat();
break;
case JOIN_CHAT:
joinChat();
break;
case SEND_PRIVATE_MESSAGES:
sendPrivateMessage();
break;
case READ_NEW_MESSAGES:
showNewMessages();
break;
case QUIT:
logout();
break;
case REGISTRATION:
registration();
break;
case CONNECT_TO_PRIVATE_CHAT:
joinToPrivateChat();
break;
default:
break;
}
} catch (IOException e) {
log.warning("Error while reading decition from keyboard. "
+ e.getMessage());
}
}
}
}
private void sendPrivateMessage() throws IOException {
PrivateMessage privateMessage = privateMessagePopulator.populate();
privateMessage.setSenderName(currentUser);
privateMessages.add(privateMessage);
}
private void joinChat() throws IOException {
System.out.println("Exist public chat");
for (Chat chat : chats) {
System.out.println(chat.getChatName());
}
System.out.println("Enter the name of chat you wish to join");
chatName = reader.readLine();
for (Chat chat : chats) {
if (chatName.equals(chat.getChatName())) {
for (Message mes : chat.getMessages()) {
System.out.println(mes.getSenderName() + ": "
+ mes.getContent());
}
publicComunication(chat);
}
}
}
private boolean hasNewMessages() {
boolean result = false;
for (PrivateMessage privateMessage : privateMessages) {
if (currentUser.equals(privateMessage.getReceiverName())) {
result = true;
}
}
for (PrivateChat pm : pmChat) {
if (pm.getAddUserName().equals(currentUser)) {
result = true;
}
}
return result;
}
private void showNewMessages() {
if (hasNewMessages()) {
for (PrivateMessage privateMessage : privateMessages) {
if (currentUser.equals(privateMessage.getReceiverName())
&& MessageStatus.DIDNT_READ.equals(privateMessage
.getStatus())) {
System.out.println(privateMessage.getSenderName() + ": "
+ privateMessage.getContent());
}
privateMessage.setStatus(MessageStatus.ALREADY_READ);
}
}
if (hasNewMessages()) {
for (PrivateChat pm : pmChat) {
for (Message message : pm.getMessages()) {
if (pm.getAddUserName().equals(currentUser)) {
System.out.println(message.getSenderName() + ": "
+ message.getContent());
}
}
}
} else {
System.out.println("you don't have new message ");
}
}
private void registrationOrLogin() throws IOException {
String logOrReg;
System.out
.println("Hi,if you already have account - 1,\nIf you would like to register - 2");
logOrReg = reader.readLine();
if (logOrReg.equals("1")) {
login();
} else if (logOrReg.equals("2")) {
registration();
} else {
registrationOrLogin();
}
}
private boolean hasUser() {
boolean result = false;
for (Registration reg : registration) {
if (currentUser.equals(reg.getUserName())
&& password.equals(reg.getUserPassword())) {
result = true;
}
}
return result;
}
private void login() throws IOException {
System.out.println("Please,enter user name and password ");
currentUser = reader.readLine();
password = reader.readLine();
if (hasUser()) {
System.out.println("You already logged in system");
} else {
System.out.println("Wrong user name or password");
registrationOrLogin();
}
}
private void logout() throws IOException {
currentUser = null;
password = null;
registrationOrLogin();
}
private void createChat() throws IOException {
Chat chat = new Chat();
chat = publicChatPopulator.populate();
publicComunication(chat);
chats.add(chat);
}
private void joinToPrivateChat() throws IOException {
for (PrivateChat pm : pmChat) {
for (String user : pm.getUsers()) {
if (user.equals(currentUser)) {
System.out.println(pm.getChatName());
}
}
}
System.out.println("Enter the name of the chat you wish to join");
chatName = reader.readLine();
for (PrivateChat pm : pmChat) {
if (chatName.equals(pm.getChatName())) {
for (Message message : pm.getMessages()) {
System.out.println(message.getSenderName() + " "
+ message.getContent());
}
privateComunication(pm);
}
}
}
private void createPrivateChat() throws IOException {
PrivateChat privateChat = new PrivateChat();
Set<String> chatUsers = new HashSet<String>();
privateChat = privateChatPopulator.populate();
while (true) {
privateChat.setAddUserName(reader.readLine());
chatUsers.add(privateChat.getAddUserName());
privateChat.setUsers(chatUsers);
for (String user : users) {
if (user.equals(privateChat.getAddUserName())) {
System.out.println("you add too chat user - "
+ privateChat.getAddUserName());
}
}
if (privateChat.getAddUserName().equals(START_CHAT)) {
break;
}
}
privateComunication(privateChat);
pmChat.add(privateChat);
}
private void registration() throws IOException {
Registration reg = registrationPopulator.populate();
registration.add(reg);
currentUser = reg.getUserName();
users.add(reg.getUserName());
}
private void privateComunication(PrivateChat privateChat) {
while (true) {
Message message = messagePopulator.populate();
message.setSenderName(currentUser);
System.out.println(message.getSenderName());
System.out.println("\t" + message.getContent());
if (EXIT.equals(message.getContent())) {
break;
}
privateChat.setStatus(MessageStatus.DIDNT_READ);
privateChat.addMessage(message);
}
}
private void publicComunication(Chat chat) {
while (true) {
Message message = messagePopulator.populate();
message.setSenderName(currentUser);
System.out.println(message.getSenderName());
System.out.println("\t" + message.getContent());
if (EXIT.equals(message.getContent())) {
break;
}
chat.addMessage(message);
}
}
}

I never thought about improving the ugly process of creating shells; never used a switch, but a lot of if-elses, which is the same essentially.
package command.example;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
public class CommandExample implements ApplicationContext {
private final Writer writer = new BufferedWriter(new OutputStreamWriter(
System.out));
private boolean quit = false;
private Map<String, Command> commands = new HashMap<>();
{
commands.put("create", new CreateChat(this));
commands.put("join", new JoinChat(this));
commands.put("exit", new ExitCommand(this));
}
public static void main(String[] args) throws Exception {
CommandExample example = new CommandExample();
example.run();
}
public void run() throws IOException {
try (Scanner s = new Scanner(System.in)) {
writer.write("> ");
writer.flush();
while (!quit && s.hasNextLine()) {
String input = s.nextLine().trim();
// get or default is java8, alternatively you could check for null
Command command = commands.getOrDefault(input, new UnknownCommand(this, input));
command.execute();
if (!quit)
writer.write("> ");
writer.flush();
}
}
}
#Override
public void shutdown() {
quit = true;
}
#Override
public Writer getWriter() {
return writer;
}
static interface Command {
public void execute() throws IOException;
}
static abstract class AbstractCommand implements Command {
protected final ApplicationContext context;
protected final Writer writer;
public AbstractCommand(ApplicationContext context) {
this.context = context;
this.writer = context.getWriter();
}
}
static class CreateChat extends AbstractCommand {
public CreateChat(ApplicationContext context) {
super(context);
}
#Override
public void execute() throws IOException {
writer.write(String.format("Successfully created a chat!%n"));
writer.flush();
}
}
static class JoinChat extends AbstractCommand {
public JoinChat(ApplicationContext context) {
super(context);
}
#Override
public void execute() throws IOException {
writer.write(String.format("Successfully joined chat!%n"));
writer.flush();
}
}
static class UnknownCommand extends AbstractCommand {
private final String command;
public UnknownCommand(ApplicationContext context, String command) {
super(context);
this.command = command;
}
#Override
public void execute() throws IOException {
writer.write(String.format("'%s' is not a supported command!%n",
command));
writer.flush();
}
}
static class ExitCommand extends AbstractCommand {
public ExitCommand(ApplicationContext context) {
super(context);
}
#Override
public void execute() throws IOException {
writer.write(String.format("Application is shutting down!%n"));
writer.flush();
context.shutdown();
}
}
};
interface ApplicationContext {
public void shutdown();
public Writer getWriter();
}
Here you have a little start. The Command implementations should not read their input (due to separation of concern), they should specify what they want and some kind of reader should provide it to them (cf. the approach with Writer).
Furthermore I'm asking myself how one would design the QuitProgram command - without using System.exit(0).

Java Telnet Library

I am really not clear on explaining this requirement but what I need basically is a JSP page that connects to a Unix server and gets the word count of a file and displays on the JSP page. I have looked on various questions here but nothing helped. A sample code would be of much help. Thanks

Kavin, I guess you must have found some other solution or moved on by now. However, I just came across a requirement that led me to this page.
I looked through the somewhat smuckish responses on this page and many others but could not find a simple to use Telnet client at all.
I spent a little bit of time and wrote a simple client on top of Commons Net's solution. Please forgive the System.out and System.err in the code, I got it to barely work.
public static void main(String[] args) throws Exception {
SimpleTelnetClient client = new SimpleTelnetClient("localhost", 2323);
client.connect();
String result = client.waitFor("login:");
System.out.println("Got " + result);
client.send("username");
result = client.waitFor("Password:");
System.out.println("Got " + result);
client.send("password");
client.waitFor("#");
client.send("ls -al");
result = client.waitFor("#");
System.out.println("Got " + result);
client.send("exit");
}
Not sure if it will help you anymore, but perhaps it could be a starting point for others.
import java.io.InputStream;
import java.io.PrintStream;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.LinkedBlockingQueue;
import org.apache.commons.net.telnet.EchoOptionHandler;
import org.apache.commons.net.telnet.InvalidTelnetOptionException;
import org.apache.commons.net.telnet.SuppressGAOptionHandler;
import org.apache.commons.net.telnet.TelnetClient;
import org.apache.commons.net.telnet.TerminalTypeOptionHandler;
public class SimpleTelnetClient {
static class Responder extends Thread {
private StringBuilder builder = new StringBuilder();
private final SimpleTelnetClient checker;
private CountDownLatch latch;
private String waitFor = null;
private boolean isKeepRunning = true;
Responder(SimpleTelnetClient checker) {
this.checker = checker;
}
boolean foundWaitFor(String waitFor) {
return builder.toString().contains(waitFor);
}
public synchronized String getAndClearBuffer() {
String result = builder.toString();
builder = new StringBuilder();
return result;
}
#Override
public void run() {
while (isKeepRunning) {
String s;
try {
s = checker.messageQueue.take();
} catch (InterruptedException e) {
break;
}
synchronized (Responder.class) {
builder.append(s);
}
if (waitFor != null && latch != null && foundWaitFor(waitFor)) {
latch.countDown();
}
}
}
public String waitFor(String waitFor) {
synchronized (Responder.class) {
if (foundWaitFor(waitFor)) {
return getAndClearBuffer();
}
}
this.waitFor = waitFor;
latch = new CountDownLatch(1);
try {
latch.await();
} catch (InterruptedException e) {
e.printStackTrace();
return null;
}
String result = null;
synchronized (Responder.class) {
result = builder.toString();
builder = new StringBuilder();
}
return result;
}
}
static class TelnetReader extends Thread {
private final SimpleTelnetClient checker;
private final TelnetClient tc;
TelnetReader(SimpleTelnetClient checker, TelnetClient tc) {
this.checker = checker;
this.tc = tc;
}
#Override
public void run() {
InputStream instr = tc.getInputStream();
try {
byte[] buff = new byte[1024];
int ret_read = 0;
do {
ret_read = instr.read(buff);
if (ret_read > 0) {
checker.sendForResponse(new String(buff, 0, ret_read));
}
} while (ret_read >= 0);
} catch (Exception e) {
System.err.println("Exception while reading socket:" + e.getMessage());
}
try {
tc.disconnect();
checker.stop();
System.out.println("Disconnected.");
} catch (Exception e) {
System.err.println("Exception while closing telnet:" + e.getMessage());
}
}
}
private String host;
private BlockingQueue<String> messageQueue = new LinkedBlockingQueue<String>();
private int port;
private TelnetReader reader;
private Responder responder;
private TelnetClient tc;
public SimpleTelnetClient(String host, int port) {
this.host = host;
this.port = port;
}
protected void stop() {
responder.isKeepRunning = false;
responder.interrupt();
}
public void send(String command) {
PrintStream ps = new PrintStream(tc.getOutputStream());
ps.println(command);
ps.flush();
}
public void sendForResponse(String s) {
messageQueue.add(s);
}
public void connect() throws Exception {
tc = new TelnetClient();
TerminalTypeOptionHandler ttopt = new TerminalTypeOptionHandler("VT100", false, false, true, false);
EchoOptionHandler echoopt = new EchoOptionHandler(true, false, true, false);
SuppressGAOptionHandler gaopt = new SuppressGAOptionHandler(true, true, true, true);
try {
tc.addOptionHandler(ttopt);
tc.addOptionHandler(echoopt);
tc.addOptionHandler(gaopt);
} catch (InvalidTelnetOptionException e) {
System.err.println("Error registering option handlers: " + e.getMessage());
}
tc.connect(host, port);
reader = new TelnetReader(this, tc);
reader.start();
responder = new Responder(this);
responder.start();
}
public String waitFor(String s) {
return responder.waitFor(s);
}
}

Why wouldn't you just use an open source telnet client. There is bound to be several to choose from. Google lists many.