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BAEL-2846- Intro to the Java Debug Interface (eugenp#7606)
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‎java-jdi/pom.xml‎

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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<artifactId>java-jdi</artifactId>
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<version>0.1.0-SNAPSHOT</version>
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<name>java-jdi</name>
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<packaging>jar</packaging>
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<parent>
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<groupId>com.baeldung</groupId>
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<artifactId>parent-java</artifactId>
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<version>0.0.1-SNAPSHOT</version>
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<relativePath>../parent-java</relativePath>
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</parent>
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<dependencies>
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<dependency>
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<groupId>log4j</groupId>
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<artifactId>log4j</artifactId>
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<version>${log4j.version}</version>
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</dependency>
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<dependency>
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<groupId>org.slf4j</groupId>
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<artifactId>slf4j-api</artifactId>
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<version>${org.slf4j.version}</version>
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</dependency>
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<dependency>
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<groupId>ch.qos.logback</groupId>
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<artifactId>logback-classic</artifactId>
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<version>${logback.version}</version>
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</dependency>
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<dependency>
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<groupId>org.openjdk.jmh</groupId>
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<artifactId>jmh-core</artifactId>
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<version>${jmh-core.version}</version>
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</dependency>
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<dependency>
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<groupId>org.openjdk.jmh</groupId>
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<artifactId>jmh-generator-annprocess</artifactId>
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<version>${jmh-generator.version}</version>
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</dependency>
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<dependency>
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<groupId>org.apache.commons</groupId>
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<artifactId>commons-lang3</artifactId>
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<version>${commons-lang3.version}</version>
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</dependency>
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<dependency>
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<groupId>org.assertj</groupId>
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<artifactId>assertj-core</artifactId>
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<version>${assertj.version}</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>com.sun</groupId>
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<artifactId>tools</artifactId>
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<version>${tools.version}</version>
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<scope>system</scope>
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<systemPath>${java.home}/../lib/tools.jar</systemPath>
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</dependency>
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</dependencies>
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<build>
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<finalName>java-jdi</finalName>
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<resources>
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<resource>
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<directory>src/main/resources</directory>
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<filtering>true</filtering>
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</resource>
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</resources>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-javadoc-plugin</artifactId>
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<version>${maven-javadoc-plugin.version}</version>
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<configuration>
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<source>1.8</source>
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<target>1.8</target>
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</configuration>
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</plugin>
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</plugins>
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</build>
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<profiles>
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<profile>
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<id>integration</id>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-surefire-plugin</artifactId>
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<executions>
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<execution>
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<phase>integration-test</phase>
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<goals>
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<goal>test</goal>
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</goals>
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<configuration>
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<includes>
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<include>**/*IntegrationTest.java</include>
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</includes>
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</configuration>
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</execution>
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</executions>
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<configuration>
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<systemPropertyVariables>
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<test.mime>json</test.mime>
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</systemPropertyVariables>
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</configuration>
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</plugin>
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</plugins>
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</build>
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</profile>
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</profiles>
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<properties>
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<commons-lang3.version>3.5</commons-lang3.version>
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<assertj.version>3.6.1</assertj.version>
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<tool.version>1.8</tool.version>
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<org.slf4j.version>1.7.21</org.slf4j.version>
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<logback.version>1.1.7</logback.version>
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<tools.version>1.8</tools.version>
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<maven-surefire-plugin.version>2.21.0</maven-surefire-plugin.version>
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<maven-javadoc-plugin.version>3.0.0-M1</maven-javadoc-plugin.version>
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<maven-jar-plugin.version>3.0.2</maven-jar-plugin.version>
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</properties>
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</project>

‎java-jdi/src/main/java/com/baeldung/jdi/JDIExample.java‎

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package com.baeldung.jdi;
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public class JDIExample {
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public static void main(String[] args) {
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String jpda = "Java Platform Debugger Architecture";
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System.out.println("Hi Everyone, Welcome to " + jpda); //add a break point here
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String jdi = "Java Debug Interface"; //add a break point here and also stepping in here
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String text = "Today, we'll dive into " + jdi;
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System.out.println(text);
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}
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}

‎java-jdi/src/main/java/com/baeldung/jdi/JDIExampleDebugger.java‎

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package com.baeldung.jdi;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import java.io.OutputStreamWriter;
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import java.util.Map;
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import com.sun.jdi.AbsentInformationException;
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import com.sun.jdi.Bootstrap;
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import com.sun.jdi.ClassType;
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import com.sun.jdi.IncompatibleThreadStateException;
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import com.sun.jdi.LocalVariable;
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import com.sun.jdi.Location;
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import com.sun.jdi.StackFrame;
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import com.sun.jdi.VMDisconnectedException;
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import com.sun.jdi.Value;
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import com.sun.jdi.VirtualMachine;
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import com.sun.jdi.connect.Connector;
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import com.sun.jdi.connect.IllegalConnectorArgumentsException;
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import com.sun.jdi.connect.LaunchingConnector;
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import com.sun.jdi.connect.VMStartException;
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import com.sun.jdi.event.BreakpointEvent;
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import com.sun.jdi.event.ClassPrepareEvent;
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import com.sun.jdi.event.Event;
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import com.sun.jdi.event.EventSet;
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import com.sun.jdi.event.LocatableEvent;
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import com.sun.jdi.event.StepEvent;
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import com.sun.jdi.request.BreakpointRequest;
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import com.sun.jdi.request.ClassPrepareRequest;
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import com.sun.jdi.request.StepRequest;
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public class JDIExampleDebugger {
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private Class debugClass;
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private int[] breakPointLines;
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public Class getDebugClass() {
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return debugClass;
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}
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public void setDebugClass(Class debugClass) {
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this.debugClass = debugClass;
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}
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public int[] getBreakPointLines() {
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return breakPointLines;
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}
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public void setBreakPointLines(int[] breakPointLines) {
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this.breakPointLines = breakPointLines;
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}
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/**
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* Sets the debug class as the main argument in the connector and launches the VM
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* @return VirtualMachine
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* @throws IOException
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* @throws IllegalConnectorArgumentsException
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* @throws VMStartException
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*/
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public VirtualMachine connectAndLaunchVM() throws IOException, IllegalConnectorArgumentsException, VMStartException {
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LaunchingConnector launchingConnector = Bootstrap.virtualMachineManager().defaultConnector();
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Map<String, Connector.Argument> arguments = launchingConnector.defaultArguments();
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arguments.get("main").setValue(debugClass.getName());
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VirtualMachine vm = launchingConnector.launch(arguments);
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return vm;
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}
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/**
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* Creates a request to prepare the debug class, add filter as the debug class and enables it
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* @param vm
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*/
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public void enableClassPrepareRequest(VirtualMachine vm) {
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ClassPrepareRequest classPrepareRequest = vm.eventRequestManager().createClassPrepareRequest();
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classPrepareRequest.addClassFilter(debugClass.getName());
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classPrepareRequest.enable();
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}
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/**
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* Sets the break points at the line numbers mentioned in breakPointLines array
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* @param vm
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* @param event
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* @throws AbsentInformationException
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*/
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public void setBreakPoints(VirtualMachine vm, ClassPrepareEvent event) throws AbsentInformationException {
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ClassType classType = (ClassType) event.referenceType();
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for(int lineNumber: breakPointLines) {
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Location location = classType.locationsOfLine(lineNumber).get(0);
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BreakpointRequest bpReq = vm.eventRequestManager().createBreakpointRequest(location);
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bpReq.enable();
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}
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}
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/**
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* Displays the visible variables
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* @param event
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* @throws IncompatibleThreadStateException
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* @throws AbsentInformationException
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*/
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public void displayVariables(LocatableEvent event) throws IncompatibleThreadStateException, AbsentInformationException {
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StackFrame stackFrame = event.thread().frame(0);
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if(stackFrame.location().toString().contains(debugClass.getName())) {
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Map<LocalVariable, Value> visibleVariables = stackFrame.getValues(stackFrame.visibleVariables());
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System.out.println("Variables at " +stackFrame.location().toString() + " > ");
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for (Map.Entry<LocalVariable, Value> entry : visibleVariables.entrySet()) {
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System.out.println(entry.getKey().name() + " = " + entry.getValue());
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}
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}
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}
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/**
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* Enables step request for a break point
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* @param vm
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* @param event
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*/
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public void enableStepRequest(VirtualMachine vm, BreakpointEvent event) {
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//enable step request for last break point
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if(event.location().toString().contains(debugClass.getName()+":"+breakPointLines[breakPointLines.length-1])) {
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StepRequest stepRequest = vm.eventRequestManager().createStepRequest(event.thread(), StepRequest.STEP_LINE, StepRequest.STEP_OVER);
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stepRequest.enable();
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}
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}
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public static void main(String[] args) throws Exception {
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JDIExampleDebugger debuggerInstance = new JDIExampleDebugger();
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debuggerInstance.setDebugClass(JDIExample.class);
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int[] breakPoints = {6, 9};
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debuggerInstance.setBreakPointLines(breakPoints);
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VirtualMachine vm = null;
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try {
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vm = debuggerInstance.connectAndLaunchVM();
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debuggerInstance.enableClassPrepareRequest(vm);
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EventSet eventSet = null;
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while ((eventSet = vm.eventQueue().remove()) != null) {
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for (Event event : eventSet) {
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if (event instanceof ClassPrepareEvent) {
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debuggerInstance.setBreakPoints(vm, (ClassPrepareEvent)event);
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}
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if (event instanceof BreakpointEvent) {
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event.request().disable();
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debuggerInstance.displayVariables((BreakpointEvent) event);
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debuggerInstance.enableStepRequest(vm, (BreakpointEvent)event);
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}
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if (event instanceof StepEvent) {
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debuggerInstance.displayVariables((StepEvent) event);
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}
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vm.resume();
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}
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}
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} catch (VMDisconnectedException e) {
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System.out.println("Virtual Machine is disconnected.");
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} catch (Exception e) {
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e.printStackTrace();
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}
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finally {
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InputStreamReader reader = new InputStreamReader(vm.process().getInputStream());
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OutputStreamWriter writer = new OutputStreamWriter(System.out);
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char[] buf = new char[512];
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reader.read(buf);
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writer.write(buf);
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writer.flush();
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}
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}
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}

‎pom.xml‎

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<module>java-collections-conversions</module>
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<module>java-collections-maps</module>
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<module>java-collections-maps-2</module>
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<module>java-jdi</module>
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<!-- <module>java-dates</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
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<!-- <module>java-dates-2</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
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<!-- <module>java-ee-8-security-api</module> --> <!-- long running -->
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<module>java-collections-conversions</module>
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<module>java-collections-maps</module>
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<module>java-collections-maps-2</module>
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<module>java-jdi</module>
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<!-- <module>java-dates</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
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<module>java-ee-8-security-api</module>
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<module>java-lite</module>

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