Develop Reference

how to use methods or execute statements within a class

I don't know if I need more coffee, or my head is tired, but, I feel like an idiot :)
what am I doing wrong???
I want to call the methods within the class but I get complile errors.
Compilation failure: Compilation failure:
java:[35,1] error: illegal start of type
java:[35,21] error: <identifier> expected
java:[35,22] error: ';' expected
I can't execute this block in the class
//this is what doesn't work
if (custkey.contains(",")) {
String[] ck = custkey.split(",");
for ( String k : ck) {
this.loadRefDb(k);
} else {
this.loadRefDb(custkey);
}
}
my class
package com.ge.digital.fleet.dataservice.impl.processor;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.*;
import javax.naming.*;
import javax.sql.*;
import java.sql.*;
import com.ge.digital.fleet.dataservice.impl.db.RefDatabase;
public class RefReplicatedDataProcessor {
private static final Logger log = LoggerFactory.getLogger(RefReplicatedDataProcessor.class);
private RefDatabase refDb = null;
private DataSource dataSource;
private String custkey;
public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}
public void setCustkey(String custkey) {
this.custkey = custkey;
}
public void setRefDatabase(RefDatabase refDb) {
this.refDb = refDb;
}
//this is what doesn't work
if (custkey.contains(",")) {
String[] ck = custkey.split(",");
for ( String k : ck) {
this.loadRefDb(k);
} else {
this.loadRefDb(custkey);
}
}
public void loadRefDb(String custkey) throws SQLException {
log.info("Reference Replicated Data Processor :: start");
refDb.dropDb();
setAssociations(custkey);
refDb.replicationComplete();
log.info("Reference Replicated Data Processor :: Finish");
}
/***
* name: setAssociations(custkey)
* Loads/Builds the cache database with values found in mysql database
*
* returns a List of associations
* G1.DWATT,112-A-001_Gas_Turbine
* G1.ATID,112-A-001_Gas_Turbine
* G1.dvar, 112-A-001_Gas_Turbine
* ...
*/
public void setAssociations(String custkey) throws SQLException {
String reference = "";
String asset = "";
String dbname = "iprcmt1.fleet_associations"; //from old impl database - TODO new database impl
String query = "select reference, asset from " + dbname + " where custkey = ?";
try (Connection conn = dataSource.getConnection();
PreparedStatement stmt = conn.prepareStatement(query)) {
stmt.setString(1, custkey);
try (ResultSet rs = stmt.executeQuery()) {
if (! rs.next() ) {
log.info("SQL Warning ! No associations for key: " + custkey);
} else {
do {
reference = rs.getString(1);
asset = rs.getString(2);
log.info("SQL Associations reference: " + reference + " and asset: " + asset);
refDb.addRow(reference, asset);
} while (rs.next());
}
} catch (Exception ex) {
log.error("SQL Cannot Execute ResultSet Query!");
log.error(ex.getMessage());
}
} catch (Exception e) {
log.error("SQL Cannot Create DataSource Connection! Cannot Create Prepared Statement!");
log.error(e.getMessage());
}
}
}

maybe this ? :)
if (custkey.contains(",")) {
String[] ck = custkey.split(",");
for ( String k : ck) {
this.loadRefDb(k);
}
}else {
this.loadRefDb(custkey);
}

Your code is simply out of place. The code at "//this is what doesn't work" needs to be inside a method or constructor.
public RefReplicatedDataProcessor(){
//this is what didn't work
if (custkey.contains(",")) {
String[] ck = custkey.split(",");
for ( String k : ck) {
this.loadRefDb(k);
}
} else {
this.loadRefDb(custkey);
}
}

Perhaps you should run the split within a method
public void filter(){
if (custkey.contains(",")) {
String[] ck = custkey.split(",");
for ( String k : ck) {
this.loadRefDb(k);
} else {
this.loadRefDb(custkey);
}
}
}

How to use a string variable from another class

I would like to access a string variable from another class to put it into an SQlite DB but I get an error "cannot be resolved or not a field
Here is the code
timestamp.java
import java.io.File;
import java.io.IOException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
import org.apache.commons.io.FileUtils;
public class timestamp {
public static String doSomething() throws IOException {
File source = new File("C:/Users/India/Desktop/Test/Sub/Test.docx");
SimpleDateFormat sdf = new SimpleDateFormat("MM-dd-yyyy HH-mm-ss-ms");
String ts=sdf.format(source.lastModified());
System.out.print(ts);
//String[] TimeStamp = source.lastModified().toString();
String name = source.getName();
String ext = name.substring(name.lastIndexOf("."));
name = name.substring(0, name.lastIndexOf("."));
String outFileName = name + " " + ts + ext;
//System.out.println(" new file name is " + outFileName);
File destination = new File("C:/Users/India/Desktop/Test", outFileName);
FileUtils.copyFile(source,destination);
return ts;
}
public static void main (String [] args) throws IOException
{ doSomething();}}
SQLiteJDBC.java
import java.io.IOException;
import java.sql.*;
public class SQLiteJDBC{
public static void InsertValues( String args[] ) throws IOException
{ timestamp t = new timestamp();
String var = t.ts;
System.out.println(t.ts);
Connection c = null;
Statement stmt = null;
try {
Class.forName("org.sqlite.JDBC");
c = DriverManager.getConnection("jdbc:sqlite:test.db");
c.setAutoCommit(false);
System.out.println("Opened database successfully");
stmt = c.createStatement();
PreparedStatement prep1 = c.prepareStatement ("INSERT INTO ACTIONLOG VALUES (?,?, ?);") ;
prep1.setString(1, var);
prep1.addBatch();
c.setAutoCommit(false);
prep1.executeBatch();
c.setAutoCommit(true);
stmt.close();
c.commit();
c.close();
} catch ( Exception e ) {
System.err.println( e.getClass().getName() + ": " + e.getMessage() );
System.exit(0);
}
System.out.println("Records created successfully");
}
public static void main( String args[] ) throws IOException
{ InsertValues(args);
}
}
I am not able to access the ts string in the database class. I either get a NULL value or an error.
Thanks a lot in advance !

Since You are Trying to Access Local Variable from Another Class. better then that go ahead with global variable.update code like that only one line define after class
public class timestamp {
String ts;// Define Here (global variable )
}

You need to create an accessor method within the class and change 'ts' to a global variable. This way, when you instatiate this class, you can simply retrieve it using something like:
MyClass.getStringName();
where 'getStringName()' is something like:
public String getStringName()
{
return ts;
}

All of your variables are in class methods, not in class area.
In Class add variable String, not in class method.

Database connection suffers of concurrent threads

I've recently starting working on a java webapp (JSP / Servlet) that was developed by the internal developer of a company.
This app randomly doesn't return data, and inspecting the log I found some NullPointerExceptions related to the classes' member variable which holds the database connection. Following the stack trace it seems that a second thread closes the connection after it ended its task leaving the first thread without a connection.
By the needs of the company the app uses different databases, one which rules appdata, and others which contain data the app has to retrieve. So every class attached to the main servlet may connect to one or more databases depending on the task it has to accomplish.
I'm not familiar with JavaEE but giving a look at the database connection class, I see nothing which protect threads from conflicting each other.
Which is the correct way to handle such connections?
This is the code of the Database handler:
package it.metmi.mmasgis.utils;
import java.sql.*;
import java.util.ArrayList;
import java.util.HashMap;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
public class DBManager
{
private String szDatabase;
private String szUsername;
private String szPassword;
private String szError;
private Connection db;
private boolean bConnected;
private Logger logger;
public DBManager(String szDBName)
{
this(szDBName, "", "");
}
public DBManager(String szDBName, String szName, String szPass)
{
szDatabase = szDBName;
szUsername = szName;
szPassword = szPass;
bConnected = false;
szError = "";
logger = LogManager.getFormatterLogger(DBManager.class.getName());
}
public boolean connect()
{
logger.entry();
try {
Class.forName("com.mysql.jdbc.Driver");
if(!szDatabase.isEmpty())
{
String szCon = "jdbc:mysql://localhost/" + szDatabase;
if(!szUsername.isEmpty())
{
szCon += "?user=" + szUsername;
if(!szPassword.isEmpty())
szCon += "&password=" + szPassword;
}
db = DriverManager.getConnection(szCon);
bConnected = true;
} else {
logger.error("No database name!!");
System.exit(0);
}
} catch(SQLException | ClassNotFoundException e) {
szError = e.getMessage();
e.printStackTrace();
logger.error("Can't connect: %s", e);
}
return logger.exit(bConnected);
}
public void disconnect()
{
logger.entry();
try {
db.close();
bConnected = false;
} catch(SQLException e) {
e.printStackTrace();
logger.error("Can't disconnect: %s", e);
}
logger.exit();
}
public boolean isConnected()
{
return bConnected;
}
public String getError()
{
return szError;
}
public ArrayList<HashMap<String,String>> query(String szQuery)
{
logger.entry(szQuery);
ArrayList<HashMap<String,String>> aResults = new ArrayList<HashMap<String,String>>();
int iCols = 0;
try {
Statement stmt = db.createStatement();
logger.info("Query: %s", szQuery);
ResultSet rs = stmt.executeQuery(szQuery);
ResultSetMetaData rsmd = rs.getMetaData();
iCols = rsmd.getColumnCount();
while(rs.next())
{
HashMap<String,String> pv = new HashMap<String,String>();
for(int i = 0; i < iCols; i++)
{
String szCol = rsmd.getColumnLabel(i + 1);
String szVal = rs.getString(i + 1);
pv.put(szCol, szVal);
}
aResults.add(pv);
}
rs.close();
stmt.close();
} catch(SQLException e) {
e.printStackTrace();
szError = e.getMessage();
logger.error("Error executing query: %s", e);
}
return logger.exit(aResults);
}
public boolean update(String szQuery)
{
logger.entry(szQuery);
boolean bResult = false;
try {
Statement stmt = db.createStatement();
logger.info("Query: %s", szQuery);
stmt.executeUpdate(szQuery);
bResult = true;
stmt.close();
} catch(SQLException e) {
e.printStackTrace();
szError = e.getMessage();
bResult = false;
logger.error("Error executing query: %s", e);
}
return logger.exit(bResult);
}
}
The class Task which all the servlet classes are based on, is a simple abstract class:
package it.metmi.mmasgis.servlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public abstract class Task
{
public abstract void doTask(HttpServletRequest request, HttpServletResponse response);
}
The class which throws NullPointerExceptions it this one, during the invocation of db.disconnect(). This class is called rapidly via AJAX 4 or 5 times from the interface written in JS.
package it.metmi.mmasgis.servlet.params;
import it.metmi.mmasgis.servlet.Task;
import it.metmi.mmasgis.utils.Const;
import it.metmi.mmasgis.utils.DBManager;
import it.metmi.mmasgis.utils.Query;
import it.metmi.mmasgis.utils.Utility;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashMap;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
public class ClassType extends Task
{
private DBManager db = null;
private Logger logger = LogManager.getFormatterLogger(ClassType.class.getName());
#Override
public void doTask(HttpServletRequest request, HttpServletResponse response)
{
logger.entry(request, response);
String szCensimento = Utility.getParameter(request, "censimento");
String szCategoria = Utility.getParameter(request, "category");
ArrayList<HashMap<String,String>> aClasses = new ArrayList<HashMap<String,String>>();
PrintWriter out = null;
logger.debug("Census: %s", szCensimento);
logger.debug("Category: %s", szCategoria);
db = new DBManager(szCensimento, Const.DB_USER, Const.DB_PASS);
if(db.connect())
{
String szQuery = String.format(Query.classes, szCategoria, szCategoria);
aClasses = db.query(szQuery);
db.disconnect();
}
try {
out = response.getWriter();
jsonEncode(aClasses, out);
} catch(IOException e) {
e.printStackTrace();
logger.error("Failed to encode JSON: %s", e);
}
logger.exit();
}
private void jsonEncode(ArrayList<HashMap<String,String>> aData, PrintWriter out)
{
HashMap<String,Object> result = new HashMap<String,Object>();
result.put("results", aData);
result.put("success", true);
Gson gson = new GsonBuilder().create();
gson.toJson(result, out);
}
}
If the webapp would use only one database, it could be rewritten as a Singleton, but in this way I have no idea on how to handle different connections for different databases.
How can avoid these exceptions?

The problem was that the connection object was declared as member.
Moving the variable inside the methods resolved.

How to use Autocomplete Field with sqlite?

I'm trying to use this code. Which is an auto-complete field that use the database.
import java.util.Vector;
import net.rim.device.api.collection.util.*;
import net.rim.device.api.database.Cursor;
import net.rim.device.api.database.Database;
import net.rim.device.api.database.DatabaseFactory;
import net.rim.device.api.database.Row;
import net.rim.device.api.database.Statement;
import net.rim.device.api.ui.*;
import net.rim.device.api.ui.container.*;
import net.rim.device.api.ui.component.*;
public class AutoCompleteFieldDemo extends UiApplication
{
public static void main(String[] args)
{
AutoCompleteFieldDemo app = new AutoCompleteFieldDemo();
app.enterEventDispatcher();
}
public AutoCompleteFieldDemo()
{
pushScreen(new AutoCompleteFieldDemoScreen());
}
public static String[] getDataFromDB()
{
Vector names = new Vector();
try
{
Database db = DatabaseFactory.openOrCreate("database1.db");
Statement statement1 = db.createStatement("SELECT name FROM Directory_Items");
statement1.prepare();
statement1.execute();
Cursor c = statement1.getCursor();
Row r;
while(c.next())
{
r = c.getRow();
names.addElement(r.getString(0));
}
statement1.close();
db.close();
}
catch( Exception e )
{
System.out.println( e.getMessage() );
e.printStackTrace();
}
String [] returnValues = new String[names.size()];
for (int i = 0; i < names.size(); i++) {
returnValues[i] = (String) names.elementAt(i);
}
return returnValues;
}
static final class AutoCompleteFieldDemoScreen extends MainScreen
{
AutoCompleteFieldDemoScreen()
{
BasicFilteredList filterLst = new BasicFilteredList();
filterLst.addDataSet(1,getDataFromDB()
,"Names",BasicFilteredList.COMPARISON_IGNORE_CASE)​;
AutoCompleteField autoFld = new AutoCompleteField(filterLst);
add(autoFld);
}
I found it in here
The problem that I'm facing is, I can't find the database. I have created the database in the SD card and I put the name in the createOropen("myDataBase.db). But When I debug it jump to the exception. Any idea about why I'm having this problem.
Thank you so much!

URLClassLoader does not read external JAR library of a plugin

I have implemented a simple plugin based application with Java. Main plugin class is derived from and abstract class called "Plugin". The application reads that class from JAR file and runs the plugin by creating an instance of the class. Standard procedure I guess :)
Everything forks fine until now. But the problem occurs when I include a library to my plugin, like MySQL Connector. The exception NoClassDefFoundError and ClassNotFoundException are thrown after execution. I am overcoming the problem by adding MySQL connector library to the main application but what is the point then? :)
I am not a Java expert so I am not sure of any alternative solutions like defining a classpath for libraries etc.
Here is my plugin loader:
http://pastebin.com/90rQ9NfJ
And here is my plugin base class:
http://pastebin.com/Juuicwkm
I am executing from a GUI:
private void jButtonAddActionPerformed(java.awt.event.ActionEvent evt) {
JFileChooser fileChooser = new JFileChooser();
fileChooser.setFileFilter(new FileNameExtensionFilter("JTask Plugin (*.JAR)", "JAR"));
if (fileChooser.showOpenDialog(this) == JFileChooser.APPROVE_OPTION)
{
File pluginFile = fileChooser.getSelectedFile();
PluginLoader pluginLoader = new PluginLoader();
Plugin plugin = pluginLoader.loadPlugin(pluginFile);
if (plugin != null)
jPanelPlugins.add(new PluginControl(jPanelPlugins, plugin));
}
}

You should really include your source code as well.
How are you executing the class i.e. via command line or from a GUI? If from the command line, then the MySQLConnector libraries, along with any other dependent library must be included in the classpath (java -classpath). The top answer to this question should help you- Java: how to import a jar file from command line

if the case, your class is a Mysql Driver you have to exclude (at the time the class is calling) classes that are not available. In the Folder of your .jar file there is one with the name "integration" it contains "jboss" and "c3p0" which are not present at this time.
while (en.hasMoreElements()) {
JarEntry entry = new JarEntry(en.nextElement());
String name = entry.getName();
if (name.contains("/integration/")) {
continue;
} else {
if (!entry.isDirectory() && name.toLowerCase().endsWith(".class"))
{
classList.add(name.replace(".class", ""));
}
}
}
This should load a mysql.xxx.jar file.
Try This
dynamicload.java
package dynamicloading;
import java.io.File;
import java.net.URL;
import java.net.URLClassLoader;
import java.sql.Connection;
import java.sql.Statement;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.DriverPropertyInfo;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Enumeration;
import java.util.Properties;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
/**
*
* #author Administrator
*/
class com_mysql_jdbc_Driver implements Driver {
private Driver driver;
com_mysql_jdbc_Driver(Driver cmjd) {
this.driver = cmjd;
}
#Override
public boolean acceptsURL(String aurlS) throws SQLException {
return this.driver.acceptsURL(aurlS);
}
#Override
public Connection connect(String aurlS, Properties pP) throws SQLException {
return this.driver.connect(aurlS, pP);
}
#Override
public int getMajorVersion() {
return this.driver.getMajorVersion();
}
#Override
public int getMinorVersion() {
return this.driver.getMinorVersion();
}
#Override
public DriverPropertyInfo[] getPropertyInfo(String aurlS, Properties pP) throws SQLException {
return this.driver.getPropertyInfo(aurlS, pP);
}
#Override
public boolean jdbcCompliant() {
return this.driver.jdbcCompliant();
}
}
public class DynMain {
/**
* #param args the command line arguments
*/
public static void main(String[] args) throws Exception {
/* please set to your path*/
File file = new File("U:/mozsamples/mysql-connector-java-5.1.19-bin.jar");
Driver cmjdD;
String aktCS;
String urlS = "jdbc:mysql://localhost/db";
String userS = "must-be-set";
String passS = "must-be-set";
Connection con;
Statement stmt;
URLClassLoader clazzLoader = URLClassLoader.newInstance(new URL[]{file.toURI().toURL()});
JarFile jarFile = new JarFile(file);
Enumeration<JarEntry> entries = jarFile.entries();
while (entries.hasMoreElements()) {
JarEntry element = entries.nextElement();
if (element.getName().endsWith(".class")) {
String name = element.getName();
if (name.contains("/integration/")) {
System.out.println( "ignored: " + name );
continue;
} else
{
try {
aktCS = element.getName().replaceAll(".class", "").replaceAll("/", ".");
clazzLoader.loadClass(aktCS);
if (name.contains("com/mysql/jdbc/Driver")) {
cmjdD = (Driver)Class.forName(aktCS, true, clazzLoader).newInstance();
try {
DriverManager.registerDriver(new com_mysql_jdbc_Driver(cmjdD));
System.out.println( "register Class: " + aktCS );
} catch (SQLException e) {
e.printStackTrace();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
try {
con = DriverManager.getConnection(urlS,userS,passS);
stmt = con.createStatement();
/*ResultSet rs = stmt.executeQuery("select * from idcart where ID=255"); */
stmt.close();
} catch (SQLException esql) {
esql.printStackTrace();
}
int j=0 ;
System.out.println("loaded Driver----------------------------------");
for( Enumeration en = DriverManager.getDrivers() ; en.hasMoreElements() ; j++)
System.out.println( en.nextElement().getClass().getName() );
if (j==0) { System.out.println("Driverlist empty"); }
System.out.println("-----------------------------------------------");
}
}
Output:
register Class: com.mysql.jdbc.Driver
ignored: com/mysql/jdbc/integration/c3p0/MysqlConnectionTester.class
ignored: com/mysql/jdbc/integration/jboss/ExtendedMysqlExceptionSorter.class
ignored: com/mysql/jdbc/integration/jboss/MysqlValidConnectionChecker.class
loaded Driver----------------------------------
sun.jdbc.odbc.JdbcOdbcDriver
dynamicloading.com_mysql_jdbc_Driver
-----------------------------------------------
OK ???