Develop Reference

using keepalive in closeablehttpclient

I have some code as follow:
public class HttpUtil {
public static String sendGetRequest(String url) {
String result = null;
try (CloseableHttpClient httpclient = HttpClients.createDefault()) {
HttpGet httpget = new HttpGet(url);
CloseableHttpResponse response = httpclient.execute(httpget);
HttpEntity entity = response.getEntity();
if (entity != null) {
result = EntityUtils.toString(entity);
}
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
}
I want to know the connection is long connection as using keepalive in HTTP 1.1 when I using sendGetRequest. I want to use long connection in java.

Default Connection keep alive strategy is keep alive indefinitely
If the Keep-Alive header is not present in the response, HttpClient assumes the connection can be kept alive indefinitely.
To customize CloseableHttpClient's keep-alive strategy use setKeepAliveStrategy:
CloseableHttpClient client = HttpClients.custom()
.setKeepAliveStrategy(myStrategy)
.build();

How to use the apache HttpClient without manager?

Although the normal usage for HttpClient works fine, I'm having difficulty wrapping my head around the connection manager part.
Neither the BasicHttpClientConnectionManager nor the PoolingHttpClientConnectionManager seem to fulfil my use case. I am running in a JEE application server and use HttpClient for consuming rest services.
From the documentation:
BasicHttpClientConnectionManager is a simple connection manager that maintains only one connection at a time. [...]
This connection manager implementation should be used inside an EJB container.
But I would like to do some pooling, and preferably my own pooling (e.g. JCA adapter). I would like to simply create an HttpClient and have my own separate pool with HttpClients without the connection manager.
Any suggestions or solutions?

You cannot really do that with HttpClient but you can with HttpCore, the transport toolkit HttpClient is based on
public static void main(String[] args) throws Exception {
HttpProcessor httpproc = HttpProcessorBuilder.create()
.add(new RequestContent())
.add(new RequestTargetHost())
.add(new RequestConnControl())
.add(new RequestUserAgent("Test/1.1"))
.add(new RequestExpectContinue(true)).build();
HttpRequestExecutor httpexecutor = new HttpRequestExecutor();
HttpCoreContext coreContext = HttpCoreContext.create();
HttpHost host = new HttpHost("localhost", 8080);
coreContext.setTargetHost(host);
DefaultBHttpClientConnection conn = new DefaultBHttpClientConnection(8 * 1024);
ConnectionReuseStrategy connStrategy = DefaultConnectionReuseStrategy.INSTANCE;
try {
String[] targets = {
"/",
"/servlets-examples/servlet/RequestInfoExample",
"/somewhere%20in%20pampa"};
for (int i = 0; i < targets.length; i++) {
if (!conn.isOpen()) {
Socket socket = new Socket(host.getHostName(), host.getPort());
conn.bind(socket);
}
BasicHttpRequest request = new BasicHttpRequest("GET", targets[i]);
System.out.println(">> Request URI: " + request.getRequestLine().getUri());
httpexecutor.preProcess(request, httpproc, coreContext);
HttpResponse response = httpexecutor.execute(request, conn, coreContext);
httpexecutor.postProcess(response, httpproc, coreContext);
System.out.println("<< Response: " + response.getStatusLine());
System.out.println(EntityUtils.toString(response.getEntity()));
System.out.println("==============");
if (!connStrategy.keepAlive(response, coreContext)) {
conn.close();
} else {
System.out.println("Connection kept alive...");
}
}
} finally {
conn.close();
}
The sample code is taken from here

Connection to server times out android

I am trying to check if server is online in android.
I have following code on a button onclick listener block:
boolean exists = false;
try {
SocketAddress sockaddr = new InetSocketAddress("google.com", 80);
// Create an unbound socket
Socket sock = new Socket();
// This method will block no more than timeoutMs.
// If the timeout occurs, SocketTimeoutException is thrown.
int timeoutMs = 2000; // 2 seconds
sock.connect(sockaddr, timeoutMs);
exists = true;
}catch(Exception e){
}
if ( exists == true) {
Toast.makeText(getApplicationContext(), "Host is reachable!!! =)",
Toast.LENGTH_LONG).show();
}
else {
Toast.makeText(getApplicationContext(), "Host is NOT reachable!!! =(",
Toast.LENGTH_LONG).show();
}
Thing is that, whatever host or ip i check, its always offline.
What could be the problem?
I have this permission in androidmanifest:
<uses-permission android:name = "android.permission.INTERNET"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

I prefer to use HttpClient. Something like:
getURL = "http://www.msftncsi.com/ncsi.txt"
HttpGet getHttp = new HttpGet(getURL);
HttpParams httpParameters = new BasicHttpParams();
int timeoutConnection = 3000;
HttpConnectionParams.setConnectionTimeout(httpParameters, timeoutConnection);
int timeoutSocket = 3000;
HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket);
HttpClient client = new DefaultHttpClient(httpParameters);
HttpResponse responseGet = client.execute(getHttp);
HttpEntity resEntityGet = responseGet.getEntity();
If HttpEntity returns null then I assume there is no connectivity.
You must surround with try catch and assume there is no connectivity when enter in the catch

Try this
InetAddress.getByName(host).isReachable(timeOut)
or
boolean exists = false;
try {
SocketAddress sockaddr = new InetSocketAddress(ip, port);
// Create an unbound socket
Socket sock = new Socket();
// This method will block no more than timeoutMs.
// If the timeout occurs, SocketTimeoutException is thrown.
int timeoutMs = 2000; // 2 seconds
sock.connect(sockaddr, timeoutMs);
exists = true;
}catch(Exception e){
}

Add Jersey client to my Android application.Illegal Argument Exception occured?

I want to use Jersey Client in my Android application.
This is the code for my client:
private JSONArray getJsonElements(){
ClientConfig config = new DefaultClientConfig();
Client client = Client.create(config);
WebResource service = client.resource(getBaseURI());
JSONArray jarray = new JSONArray();
jarray = service.path("/collection").accept(MediaType.APPLICATION_JSON).get(JSONArray.class);
Log.v(TAG, jarray.toString());
return jarray;
}
private static URI getBaseURI() {
return UriBuilder.fromUri("http://localhost:6577/Example/rest/Example")
.build();
}
And here comes the problem.When i want to build application it gives me this very common exception:
java.lang.IllegalArgumentException: already added: Ljavax/ws/rs/core/GenericEntity;...2012-07-07 16:48:32 - SM] Conversion to Dalvik format failed with error 1
I saw all questions that were asked about this exception.It is possible to remove Jars from BuildPath and change choice of client(or I can create my client),but I don't want to do this.
What can you recommend to me?

Take a look in this link : http://www.vogella.com/articles/AndroidNetworking/article.html
I myself prefer to use HTTP Client to connect the Android application to a Rest Service using Jersey since it supports the HTTP commands such as POST, PUT, DELETE, GET. For example to use GET command and trasferring data in JSON format:
public class Client {
private String server;
public Client(String server) {
this.server = server;
}
private String getBase() {
return server;
}
public String getBaseURI(String str) {
String result = "";
try {
HttpParams httpParameters = new BasicHttpParams();
int timeoutConnection = 3000;
HttpConnectionParams.setConnectionTimeout(httpParameters, timeoutConnection);
int timeoutSocket = 5000;
HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket);
DefaultHttpClient httpClient = new DefaultHttpClient(httpParameters);
HttpGet getRequest = new HttpGet(getBase() + str);
getRequest.addHeader("accept", "application/json");
HttpResponse response = httpClient.execute(getRequest);
result = getResult(response).toString();
httpClient.getConnectionManager().shutdown();
} catch (Exception e) {
System.out.println(e.getMessage());
}
return result;
}
private StringBuilder getResult(HttpResponse response) throws IllegalStateException, IOException {
StringBuilder result = new StringBuilder();
BufferedReader br = new BufferedReader(new InputStreamReader((response.getEntity().getContent())), 1024);
String output;
while ((output = br.readLine()) != null)
result.append(output);
return result;
}
}
And then easily in another class you can:
Client client = new Client("http://localhost:6577/Example/rest/");
String str = client.getBaseURI("Example"); // Json format

Migrate from Commons HttpClient to HttpComponents Client

I would like to migrate from Commons HttpClient (3.x) to HttpComponents Client (4.x) but having difficulty how to handle redirects. The code works properly under Commons HttpClient but breaks when migrated to HttpComponents Client. Some of the links get undesirable redirects but when I set "http.protocol.handle-redirects" to 'false' a large number links stop working altogether.
Commons HttpClient 3.x:
private static HttpClient httpClient = null;
private static MultiThreadedHttpConnectionManager connectionManager = null;
private static final long MAX_CONNECTION_IDLE_TIME = 60000; // milliseconds
static {
//HttpURLConnection.setFollowRedirects(true);
CookieManager manager = new CookieManager();
manager.setCookiePolicy(CookiePolicy.ACCEPT_ALL);
CookieHandler.setDefault(manager);
connectionManager = new MultiThreadedHttpConnectionManager();
connectionManager.getParams().setDefaultMaxConnectionsPerHost(1000); // will need to set from properties file
connectionManager.getParams().setMaxTotalConnections(1000);
httpClient = new HttpClient(connectionManager);
}
/*
* Retrieve HTML
*/
public String fetchURL(String url) throws IOException{
if ( StringUtils.isEmpty(url) )
return null;
GetMethod getMethod = new GetMethod(url);
HttpClient httpClient = new HttpClient();
//configureMethod(getMethod);
//ObjectInputStream oin = null;
InputStream in = null;
int code = -1;
String html = "";
String lastModified = null;
try {
code = httpClient.executeMethod(getMethod);
in = getMethod.getResponseBodyAsStream();
//oin = new ObjectInputStream(in);
//html = getMethod.getResponseBodyAsString();
html = CharStreams.toString(new InputStreamReader(in));
}
catch (Exception except) {
}
finally {
try {
//oin.close();
in.close();
}
catch (Exception except) {}
getMethod.releaseConnection();
connectionManager.closeIdleConnections(MAX_CONNECTION_IDLE_TIME);
}
if (code <= 400){
return html.replaceAll("\\s+", " ");
} else {
throw new Exception("URL: " + url + " returned response code " + code);
}
}
HttpComponents Client 4.x :
private static HttpClient httpClient = null;
private static HttpParams params = null;
//private static MultiThreadedHttpConnectionManager connectionManager = null;
private static ThreadSafeClientConnManager connectionManager = null;
private static final int MAX_CONNECTION_IDLE_TIME = 60000; // milliseconds
static {
//HttpURLConnection.setFollowRedirects(true);
CookieManager manager = new CookieManager();
manager.setCookiePolicy(CookiePolicy.ACCEPT_ALL);
CookieHandler.setDefault(manager);
connectionManager = new ThreadSafeClientConnManager();
connectionManager.setDefaultMaxPerRoute(1000); // will need to set from properties file
connectionManager.setMaxTotal(1000);
httpClient = new DefaultHttpClient(connectionManager);
// HTTP parameters stores header etc.
params = new BasicHttpParams();
params.setParameter("http.protocol.handle-redirects",false);
}
/*
* Retrieve HTML
*/
public String fetchURL(String url) throws IOException{
if ( StringUtils.isEmpty(url) )
return null;
InputStream in = null;
//int code = -1;
String html = "";
// Prepare a request object
HttpGet httpget = new HttpGet(url);
httpget.setParams(params);
// Execute the request
HttpResponse response = httpClient.execute(httpget);
// The response status
//System.out.println(response.getStatusLine());
int code = response.getStatusLine().getStatusCode();
// Get hold of the response entity
HttpEntity entity = response.getEntity();
// If the response does not enclose an entity, there is no need
// to worry about connection release
if (entity != null) {
try {
//code = httpClient.executeMethod(getMethod);
//in = getMethod.getResponseBodyAsStream();
in = entity.getContent();
html = CharStreams.toString(new InputStreamReader(in));
}
catch (Exception except) {
throw new Exception("URL: " + url + " returned response code " + code);
}
finally {
try {
//oin.close();
in.close();
}
catch (Exception except) {}
//getMethod.releaseConnection();
connectionManager.closeIdleConnections(MAX_CONNECTION_IDLE_TIME, TimeUnit.MILLISECONDS);
connectionManager.closeExpiredConnections();
}
}
if (code <= 400){
return html;
} else {
throw new Exception("URL: " + url + " returned response code " + code);
}
}
I won't want redirects but under HttpClient 4.x if I enable redirects then I get some that are undesirable, e.g. http://www.walmart.com/ => http://mobile.walmart.com/. Under HttpClient 3.x no such redirects happens.
What do I need to do to migrate HttpClient 3.x to HttpClient 4.x without breaking the code?

It is not the issue with HttpClient 4.x, might be the way target server handle the request, since the user agent is httpclient, it may be handled as mobile (target server may consider other than available browsers like, i.e, chrome, mozilla etc as mobile.)
Please use below code to set it manually
httpclient.getParams().setParameter(
org.apache.http.params.HttpProtocolParams.USER_AGENT,
"Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.2) Gecko/20100316 Firefox/3.6.2"
);