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lor6lor6
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Merge pull request eugenp#2972 from denis-zhdanov/BAEL-1290-javac-plugin
BAEL-1290 Creating a Java Compiler Plugin
2 parents 996bee2 + 8e5e0e3 commit b383d83

10 files changed

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‎core-java/pom.xml‎

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<artifactId>spring-web</artifactId>
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<version>4.3.4.RELEASE</version>
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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>1.8.0</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>

‎core-java/src/main/java/com/baeldung/javac/Positive.java‎

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package com.baeldung.javac;
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import java.lang.annotation.*;
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@Documented
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@Retention(RetentionPolicy.CLASS)
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@Target({ElementType.PARAMETER})
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public @interface Positive {
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}

‎core-java/src/main/java/com/baeldung/javac/SampleJavacPlugin.java‎

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package com.baeldung.javac;
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import com.sun.source.tree.MethodTree;
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import com.sun.source.tree.VariableTree;
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import com.sun.source.util.*;
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import com.sun.tools.javac.api.BasicJavacTask;
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import com.sun.tools.javac.code.TypeTag;
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import com.sun.tools.javac.tree.JCTree;
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import com.sun.tools.javac.tree.TreeMaker;
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import com.sun.tools.javac.util.Context;
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import com.sun.tools.javac.util.Name;
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import com.sun.tools.javac.util.Names;
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import javax.tools.JavaCompiler;
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import java.util.*;
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import java.util.stream.Collectors;
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import static com.sun.tools.javac.util.List.nil;
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/**
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* A {@link JavaCompiler javac} plugin which inserts {@code >= 0} checks into resulting {@code *.class} files
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* for numeric method parameters marked by {@link Positive}
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*/
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public class SampleJavacPlugin implements Plugin {
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public static final String NAME = "MyPlugin";
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private static Set<String> TARGET_TYPES = new HashSet<>(Arrays.asList(
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// Use only primitive types for simplicity
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byte.class.getName(), short.class.getName(), char.class.getName(), int.class.getName(),
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long.class.getName(), float.class.getName(), double.class.getName()
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));
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@Override
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public String getName() {
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return NAME;
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}
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@Override
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public void init(JavacTask task, String... args) {
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Context context = ((BasicJavacTask) task).getContext();
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task.addTaskListener(new TaskListener() {
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@Override
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public void started(TaskEvent e) {
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}
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@Override
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public void finished(TaskEvent e) {
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if (e.getKind() != TaskEvent.Kind.PARSE) {
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return;
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}
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e.getCompilationUnit().accept(new TreeScanner<Void, Void>() {
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@Override
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public Void visitMethod(MethodTree method, Void v) {
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List<VariableTree> parametersToInstrument = method.getParameters()
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.stream()
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.filter(SampleJavacPlugin.this::shouldInstrument)
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.collect(Collectors.toList());
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if (!parametersToInstrument.isEmpty()) {
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// There is a possible case that more than one argument is marked by @Positive,
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// as the checks are added to the method's body beginning, we process parameters RTL
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// to ensure correct order.
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Collections.reverse(parametersToInstrument);
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parametersToInstrument.forEach(p -> addCheck(method, p, context));
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}
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// There is a possible case that there is a nested class declared in a method's body,
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// hence, we want to proceed with method body AST as well.
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return super.visitMethod(method, v);
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}
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}, null);
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}
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});
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}
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private boolean shouldInstrument(VariableTree parameter) {
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return TARGET_TYPES.contains(parameter.getType().toString())
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&& parameter.getModifiers().getAnnotations()
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.stream()
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.anyMatch(a -> Positive.class.getSimpleName().equals(a.getAnnotationType().toString()));
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}
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private void addCheck(MethodTree method, VariableTree parameter, Context context) {
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JCTree.JCIf check = createCheck(parameter, context);
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JCTree.JCBlock body = (JCTree.JCBlock) method.getBody();
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body.stats = body.stats.prepend(check);
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}
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private static JCTree.JCIf createCheck(VariableTree parameter, Context context) {
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TreeMaker factory = TreeMaker.instance(context);
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Names symbolsTable = Names.instance(context);
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String parameterName = parameter.getName().toString();
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String errorMessagePrefix = String.format("Argument '%s' of type %s is marked by @%s but got '",
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parameterName, parameter.getType(), Positive.class.getSimpleName());
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String errorMessageSuffix = "' for it";
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Name parameterId = symbolsTable.fromString(parameterName);
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return factory.at(((JCTree) parameter).pos).If(
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factory.Parens(
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factory.Binary(
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JCTree.Tag.LE,
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factory.Ident(parameterId),
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factory.Literal(TypeTag.INT, 0))
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),
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factory.Block(0, com.sun.tools.javac.util.List.of(
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factory.Throw(
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factory.NewClass(
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null,
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nil(),
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factory.Ident(
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symbolsTable.fromString(IllegalArgumentException.class.getSimpleName())
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),
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com.sun.tools.javac.util.List.of(
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factory.Binary(JCTree.Tag.PLUS,
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factory.Binary(JCTree.Tag.PLUS,
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factory.Literal(TypeTag.CLASS, errorMessagePrefix),
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factory.Ident(parameterId)),
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factory.Literal(TypeTag.CLASS, errorMessageSuffix))),
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null
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)
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)
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)),
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null
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);
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}
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}

‎core-java/src/main/resources/META-INF/services/com.sun.source.util.Plugin‎

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com.baeldung.javac.SampleJavacPlugin

‎core-java/src/test/java/com/baeldung/javac/SampleJavacPluginIntegrationTest.java‎

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package com.baeldung.javac;
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import org.junit.Test;
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import static org.junit.Assert.assertEquals;
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public class SampleJavacPluginIntegrationTest {
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private static final String CLASS_TEMPLATE =
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"package com.baeldung.javac;\n" +
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"\n" +
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"public class Test {\n" +
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" public static %1$s service(@Positive %1$s i) {\n" +
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" return i;\n" +
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" }\n" +
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"}\n" +
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"";
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private TestCompiler compiler = new TestCompiler();
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private TestRunner runner = new TestRunner();
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@Test(expected = IllegalArgumentException.class)
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public void givenInt_whenNegative_thenThrowsException() throws Throwable {
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compileAndRun(double.class,-1);
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}
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@Test(expected = IllegalArgumentException.class)
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public void givenInt_whenZero_thenThrowsException() throws Throwable {
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compileAndRun(int.class,0);
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}
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@Test
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public void givenInt_whenPositive_thenSuccess() throws Throwable {
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assertEquals(1, compileAndRun(int.class, 1));
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}
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private Object compileAndRun(Class<?> argumentType, Object argument) throws Throwable {
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String qualifiedClassName = "com.baeldung.javac.Test";
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byte[] byteCode = compiler.compile(qualifiedClassName, String.format(CLASS_TEMPLATE, argumentType.getName()));
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return runner.run(byteCode, qualifiedClassName, "service", new Class[] {argumentType}, argument);
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}
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}

‎core-java/src/test/java/com/baeldung/javac/SimpleClassFile.java‎

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package com.baeldung.javac;
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import javax.tools.SimpleJavaFileObject;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import java.io.OutputStream;
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import java.net.URI;
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/** Holds compiled byte code in a byte array */
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public class SimpleClassFile extends SimpleJavaFileObject {
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private ByteArrayOutputStream out;
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public SimpleClassFile(URI uri) {
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super(uri, Kind.CLASS);
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}
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@Override
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public OutputStream openOutputStream() throws IOException {
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return out = new ByteArrayOutputStream();
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}
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public byte[] getCompiledBinaries() {
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return out.toByteArray();
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}
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}

‎core-java/src/test/java/com/baeldung/javac/SimpleFileManager.java‎

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package com.baeldung.javac;
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import javax.tools.*;
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import java.net.URI;
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import java.util.ArrayList;
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import java.util.List;
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/** Adapts {@link SimpleClassFile} to the {@link JavaCompiler} */
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public class SimpleFileManager extends ForwardingJavaFileManager<StandardJavaFileManager> {
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private final List<SimpleClassFile> compiled = new ArrayList<>();
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public SimpleFileManager(StandardJavaFileManager delegate) {
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super(delegate);
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}
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@Override
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public JavaFileObject getJavaFileForOutput(Location location,
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String className,
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JavaFileObject.Kind kind,
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FileObject sibling)
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{
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SimpleClassFile result = new SimpleClassFile(URI.create("string://" + className));
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compiled.add(result);
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return result;
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}
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/**
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* @return compiled binaries processed by the current class
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*/
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public List<SimpleClassFile> getCompiled() {
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return compiled;
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}
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}

‎core-java/src/test/java/com/baeldung/javac/SimpleSourceFile.java‎

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package com.baeldung.javac;
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import javax.tools.SimpleJavaFileObject;
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import java.net.URI;
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/** Exposes given test source to the compiler. */
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public class SimpleSourceFile extends SimpleJavaFileObject {
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private final String content;
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public SimpleSourceFile(String qualifiedClassName, String testSource) {
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super(URI.create(String.format("file://%s%s",
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qualifiedClassName.replaceAll("\\.", "/"),
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Kind.SOURCE.extension)),
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Kind.SOURCE);
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content = testSource;
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}
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@Override
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public CharSequence getCharContent(boolean ignoreEncodingErrors) {
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return content;
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}
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}

‎core-java/src/test/java/com/baeldung/javac/TestCompiler.java‎

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package com.baeldung.javac;
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import javax.tools.JavaCompiler;
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import javax.tools.ToolProvider;
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import java.io.StringWriter;
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import java.util.ArrayList;
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import java.util.List;
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import static java.util.Arrays.asList;
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import static java.util.Collections.singletonList;
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public class TestCompiler {
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public byte[] compile(String qualifiedClassName, String testSource) {
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StringWriter output = new StringWriter();
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JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
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SimpleFileManager fileManager = new SimpleFileManager(compiler.getStandardFileManager(
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null,
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null,
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null
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));
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List<SimpleSourceFile> compilationUnits = singletonList(new SimpleSourceFile(qualifiedClassName, testSource));
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List<String> arguments = new ArrayList<>();
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arguments.addAll(asList("-classpath", System.getProperty("java.class.path"),
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"-Xplugin:" + SampleJavacPlugin.NAME));
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JavaCompiler.CompilationTask task = compiler.getTask(output,
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fileManager,
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null,
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arguments,
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null,
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compilationUnits);
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task.call();
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return fileManager.getCompiled().iterator().next().getCompiledBinaries();
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}
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}

‎core-java/src/test/java/com/baeldung/javac/TestRunner.java‎

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package com.baeldung.javac;
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import java.lang.reflect.InvocationTargetException;
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import java.lang.reflect.Method;
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public class TestRunner {
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public Object run(byte[] byteCode,
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String qualifiedClassName,
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String methodName,
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Class<?>[] argumentTypes,
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Object... args)
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throws Throwable
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{
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ClassLoader classLoader = new ClassLoader() {
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@Override
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protected Class<?> findClass(String name) throws ClassNotFoundException {
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return defineClass(name, byteCode, 0, byteCode.length);
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}
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};
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Class<?> clazz;
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try {
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clazz = classLoader.loadClass(qualifiedClassName);
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} catch (ClassNotFoundException e) {
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throw new RuntimeException("Can't load compiled test class", e);
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}
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Method method;
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try {
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method = clazz.getMethod(methodName, argumentTypes);
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} catch (NoSuchMethodException e) {
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throw new RuntimeException("Can't find the 'main()' method in the compiled test class", e);
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}
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try {
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return method.invoke(null, args);
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} catch (InvocationTargetException e) {
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throw e.getCause();
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}
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}
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}

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