my favorite java tips & tricks and notes

JPA Paging

int maxRecords = 250;

int startPosition = 0;

String queryString = "SELECT u FROM test.VmUsers u where u.userCli LIKE :pattern ";

while (true){

try {

     Query selectQuery = subscriberEntityManager.createQuery (queryString);

selectQuery.setParameter ("pattern", "%"+pattern);

    selectQuery.setFirstResult(startPosition);

    selectQuery.setMaxResults (maxRecords);

    List users = selectQuery.getResultList ();

    if (users.isEmpty ()) {

        break;

    }

    startPosition = startPosition + users.size ();
 

}catch (Exception e) {

    e.printStackTrace();

}

}

Locate any java class file in your filesystem in runtime

package sunels;

import java.security.*;

import java.net.URL;

public class ClasspathUtil {

public static void main (String[] args) {

ClasspathUtil classpathutil = new ClasspathUtil ();

ProtectionDomain pDomain = classpathutil.getClass().getProtectionDomain();

CodeSource cSource = pDomain.getCodeSource();

URL loc = cSource.getLocation();

System.out.println (" -- Class< " + classpathutil.getClass().getCanonicalName() + "> Found in : {" + classpathutil.getClass().getCanonicalName() + " :" + loc+"}");

System.exit (0);

}

}

note: This example is finding itself

Sample Jmeter Java Test

package sunels;

import java.io.Serializable;

import org.apache.jmeter.protocol.java.sampler.*;

import org.apache.jmeter.config.Arguments;

import org.apache.jmeter.protocol.java.sampler.JavaSamplerContext;

import org.apache.jmeter.samplers.SampleResult;

import java.util.List;

import java.util.Properties;

import java.io.IOException;

import java.util.ArrayList;

import java.io.FileInputStream;

import com.mycompany.myproduct.um.msgstore.MessagestoreFactory;

import com.mycompany.myproduct.um.profile.ProfileFactory;

import java.util.Date;

import com.mycompany.myproduct.um.common.Language;

import com.mycompany.myproduct.um.profile.Subscriber;

import java.util.Random;

public class JmeterTest implements JavaSamplerClient , Serializable {

private static List msisdns = new ArrayList();

private static int totalRecordCount = 0;

private static java.util.Date startDate = new java.util.Date();

private static final String umModuleName = "UM";

private ProfileFactory profilefactory = ProfileFactory.getInstance (umModuleName);

private MessagestoreFactory msgstoreFactory = MessagestoreFactory.getInstance (umModuleName);

private Random randomGenerator = new Random();

private static int testType = 1;

static {

try {

Properties props = new Properties();

props.load (new FileInputStream ("/tmp/phoneNumbers.txt"));

msisdns = new ArrayList (props.keySet());

totalRecordCount = msisdns.size();

System.out.println (" -- Msisdns are loaded ....");

}

catch (IOException e) {

e.printStackTrace ();

System.exit (1);

}

}

public void setupTest(JavaSamplerContext context) {

}

public Arguments getDefaultParameters() {

Arguments params = new Arguments();

return params;

}

public synchronized String getMsisdn (){

String subscriberMsisdn = (String) msisdns.get(randomGenerator.nextInt(totalRecordCount));

return subscriberMsisdn;

}

public Subscriber playWithSubscriber (String subscriberPhoneNumber) throws Exception {

Subscriber subscriber = null;

subscriber = (Subscriber) profilefactory.querySubscriberByPhoneNumber (profilefactory.getCommonFactory ().createPhoneNumber (subscriberPhoneNumber));

if (subscriber != null) {

if(testType != 1){

Language subscriberLanguage = subscriber.getLanguage ();

if (subscriberLanguage == Language.ENGLISH) {

subscriber.setLanguage (Language.UKRAINIAN);

}

else {

subscriber.setLanguage (Language.ENGLISH);

}

Date currDate = new java.util.Date ();

subscriber.getSubscription ().setLastLoginDate (currDate);

subscriber.getSubscription ().setLastMessageActivityDate (currDate);

subscriber.save ();

}

}

else {

System.out.println (" -- Unable to find subscriber with msisdn :" + subscriberPhoneNumber);

}

return subscriber;

}

public SampleResult runTest(JavaSamplerContext context) {

SampleResult results = new SampleResult();

results.sampleStart();

String msisdn = getMsisdn();

try{

playWithSubscriber (msisdn);

results.setSuccessful(true);

results.setResponseCodeOK();

results.setResponseMessage("Subscriber found:" + msisdn);

} catch (Exception ex){

ex.printStackTrace();

results.setSuccessful(true);

results.setResponseCode("Exception*");

results.setResponseMessage("Subscriber not found:" + msisdn);

}

results.sampleEnd();

return results;

}

public void teardownTest(JavaSamplerContext context) {

}

}

Executing linux commands from Java

package sunels;

import java.io.*;

public class LinuxCommandExecutor {

public static void main (String args[]) {

try {

ProcessBuilder pb = new ProcessBuilder ("/bin/grep", "phoneNumber", "/space/subscribersDBdump.txt");

Process proc = pb.start ();

BufferedInputStream in = new BufferedInputStream (proc.getInputStream ());

FileOutputStream fout = new FileOutputStream ("/space/phoneNumbersOnly.txt");

byte[] buffer = new byte[2048];

while (true) {

int nRead = in.read (buffer);

if (nRead == -1)

break;

fout.write (buffer, 0, nRead);

System.out.print (".");

}

fout.close ();

proc.waitFor ();

}

catch (Exception e) {

e.printStackTrace ();

}

}

}