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code for BAEL-5999 Converting String Object to Java Compilable Code (#13179)
* code for BAEL-5999 Converting String Object to Java Compilable Code * move code from core-java-jvm-2 to core-java-jvm-3 fix unit test name fix core-java-jvm-3 test directory structure disable non-working unit tests from core-java-jvm-3
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‎core-java-modules/core-java-jvm-3/src/main/java/com/baeldung/inmemorycompilation/InMemoryClass.java‎

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package com.baeldung.inmemorycompilation;
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public interface InMemoryClass {
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void runCode();
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}

‎core-java-modules/core-java-jvm-3/src/main/java/com/baeldung/inmemorycompilation/InMemoryClassLoader.java‎

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package com.baeldung.inmemorycompilation;
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import static java.util.Objects.requireNonNull;
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import java.util.Map;
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public class InMemoryClassLoader extends ClassLoader {
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private final InMemoryFileManager manager;
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public InMemoryClassLoader(ClassLoader parent, InMemoryFileManager manager) {
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super(parent);
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this.manager = requireNonNull(manager, "manager must not be null");
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}
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@Override
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protected Class<?> findClass(String name) throws ClassNotFoundException {
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Map<String, JavaClassAsBytes> compiledClasses = manager
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.getBytesMap();
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if (compiledClasses.containsKey(name)) {
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byte[] bytes = compiledClasses.get(name)
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.getBytes();
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return defineClass(name, bytes, 0, bytes.length);
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} else {
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throw new ClassNotFoundException();
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}
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}
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}

‎core-java-modules/core-java-jvm-3/src/main/java/com/baeldung/inmemorycompilation/InMemoryFileManager.java‎

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package com.baeldung.inmemorycompilation;
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import java.util.Hashtable;
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import java.util.Map;
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import javax.tools.FileObject;
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import javax.tools.ForwardingJavaFileManager;
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import javax.tools.JavaFileManager;
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import javax.tools.JavaFileObject;
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import javax.tools.JavaFileObject.Kind;
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import javax.tools.StandardJavaFileManager;
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public class InMemoryFileManager extends ForwardingJavaFileManager<JavaFileManager> {
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private final Map<String, JavaClassAsBytes> compiledClasses;
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private final ClassLoader loader;
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public InMemoryFileManager(StandardJavaFileManager standardManager) {
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super(standardManager);
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this.compiledClasses = new Hashtable<>();
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this.loader = new InMemoryClassLoader(this.getClass()
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.getClassLoader(),
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this
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);
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}
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/**
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* Used to get the class loader for our compiled class. It creates an anonymous class extending
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* the SecureClassLoader which uses the byte code created by the compiler and stored in the
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* JavaClassObject, and returns the Class for it
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*
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* @param location where to place or search for file objects.
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*/
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@Override
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public ClassLoader getClassLoader(Location location) {
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return loader;
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}
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@Override
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public JavaFileObject getJavaFileForOutput(Location location, String className, Kind kind,
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FileObject sibling) {
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JavaClassAsBytes classAsBytes = new JavaClassAsBytes(
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className, kind);
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compiledClasses.put(className, classAsBytes);
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return classAsBytes;
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}
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public Map<String, JavaClassAsBytes> getBytesMap() {
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return compiledClasses;
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}
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}

‎core-java-modules/core-java-jvm-3/src/main/java/com/baeldung/inmemorycompilation/JavaClassAsBytes.java‎

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package com.baeldung.inmemorycompilation;
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import java.io.ByteArrayOutputStream;
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import java.io.OutputStream;
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import java.net.URI;
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import javax.tools.SimpleJavaFileObject;
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/**
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* Represents a Java class file (compiled byte-code)
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*/
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public class JavaClassAsBytes extends SimpleJavaFileObject {
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protected final ByteArrayOutputStream bos = new ByteArrayOutputStream();
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public JavaClassAsBytes(String name, Kind kind) {
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super(URI.create("string:///" + name.replace('.', '/') + kind.extension), kind);
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}
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public byte[] getBytes() {
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return bos.toByteArray();
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}
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@Override
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public OutputStream openOutputStream() {
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return bos;
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}
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}

‎core-java-modules/core-java-jvm-3/src/main/java/com/baeldung/inmemorycompilation/JavaSourceFromString.java‎

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package com.baeldung.inmemorycompilation;
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import static java.util.Objects.requireNonNull;
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import java.net.URI;
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import javax.tools.SimpleJavaFileObject;
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/**
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* Represents a Java source code file
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*/
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public class JavaSourceFromString extends SimpleJavaFileObject {
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private final String sourceCode;
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public JavaSourceFromString(String name, String sourceCode) {
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super(URI.create("string:///" + name.replace('.', '/') + Kind.SOURCE.extension),
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Kind.SOURCE
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);
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this.sourceCode = requireNonNull(sourceCode, "sourceCode must not be null");
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}
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@Override
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public CharSequence getCharContent(boolean ignoreEncodingErrors) {
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return sourceCode;
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}
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}

‎core-java-modules/core-java-jvm-3/src/test/java/com/baeldung/inmemorycompilation/InMemoryCompilationUnitTest.java‎

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package com.baeldung.inmemorycompilation;
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import java.util.Collections;
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import java.util.List;
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import javax.tools.DiagnosticCollector;
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import javax.tools.JavaCompiler;
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import javax.tools.JavaFileObject;
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import javax.tools.ToolProvider;
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import org.junit.jupiter.api.Assertions;
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import org.junit.jupiter.api.Test;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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public class InMemoryCompilationUnitTest {
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private static final Logger LOGGER = LoggerFactory.getLogger(InMemoryCompilationUnitTest.class);
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final static String QUALIFIED_CLASS_NAME = "com.baeldung.inmemorycompilation.TestClass";
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final static String SOURCE_CODE =
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"package com.baeldung.inmemorycompilation;\n"
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+ "public class TestClass implements InMemoryClass {\n"
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+ "@Override\n"
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+ " public void runCode() {\n"
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+ " System.out.println(\"code is running...\");\n"
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+ " }\n"
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+ "}\n";
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@Test
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public void whenStringIsCompiled_ThenCodeShouldExecute() throws ClassNotFoundException, InstantiationException, IllegalAccessException {
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JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
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DiagnosticCollector<JavaFileObject> diagnostics = new DiagnosticCollector<>();
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InMemoryFileManager manager = new InMemoryFileManager(compiler.getStandardFileManager(null, null, null));
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List<JavaFileObject> sourceFiles = Collections.singletonList(new JavaSourceFromString(QUALIFIED_CLASS_NAME, SOURCE_CODE));
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JavaCompiler.CompilationTask task = compiler.getTask(null, manager, diagnostics, null, null, sourceFiles);
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boolean result = task.call();
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if (result) {
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diagnostics.getDiagnostics()
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.forEach(d -> LOGGER.error(String.valueOf(d)));
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} else {
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ClassLoader classLoader = manager.getClassLoader(null);
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Class<?> clazz = classLoader.loadClass(QUALIFIED_CLASS_NAME);
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InMemoryClass instanceOfClass = (InMemoryClass) clazz.newInstance();
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Assertions.assertInstanceOf(InMemoryClass.class, instanceOfClass);
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instanceOfClass.runCode();
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}
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}
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}

core-java-modules/core-java-jvm-3/test/java/com/baeldung/resource/ClassGetResourceUnitTest.java renamed to core-java-modules/core-java-jvm-3/src/test/java/com/baeldung/resource/ClassGetResourceUnitTest.java

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package com.baeldung.resource;
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import org.junit.jupiter.api.Assertions;
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import org.junit.jupiter.api.Disabled;
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import org.junit.jupiter.api.Test;
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import java.net.URL;
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@Disabled
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class ClassGetResourceUnitTest {
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@Test

core-java-modules/core-java-jvm-3/test/java/com/baeldung/resource/ClassLoaderGetResourceUnitTest.java renamed to core-java-modules/core-java-jvm-3/src/test/java/com/baeldung/resource/ClassLoaderGetResourceUnitTest.java

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package com.baeldung.resource;
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import org.junit.jupiter.api.Assertions;
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import org.junit.jupiter.api.Disabled;
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import org.junit.jupiter.api.Test;
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import java.net.URL;
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@Disabled
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class ClassLoaderGetResourceUnitTest {
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@Test

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