自定义compiler
核心代码是JavaCompiler.CompilationTask， 通过调用JavaCompiler.CompilationTask.call方法
编译无误返回true，反之返回false
参数：out - 用于来自编译器的其他输出的 Writer；如果为 null，则使用 System.err
fileManager - 文件管理器；如果为 null，则使用编译器的标准文件管理器标准文件管理器有两个用途：
• 自定义编译器如何读写文件的基本构建块
• 在多个编译任务之间共享
diagnosticListener - 诊断侦听器；如果为 null，则使用编译器的默认方法报告诊断信息
options - 编译器选项； null 表示没有选项
classes - 类名称（用于注释处理）， null 表示没有类名称
compilationUnits - 要编译的编译单元； null 表示没有编译单元
此处我们自定了fileManager，用于接收String类型输入。编译单元是单个的String流
package io.github.kennethfan.compiler;import javax.tools.*;import java.util.ArrayList;import java.util.List;import java.util.Locale;/** * Created by kenneth on 2023/5/28. */public class RuntimeCompiler { private JavaCompiler javaCompiler; public RuntimeCompiler() { this.javaCompiler = ToolProvider.getSystemJavaCompiler(); } public Class<?> compileAndLoad(String fullName, String sourceCode) throws ClassNotFoundException { DiagnosticCollector<? super JavaFileObject> diagnosticCollector = new DiagnosticCollector<>(); JavaFileManager javaFileManager = new ClassFileManager(this.javaCompiler.getStandardFileManager(diagnosticCollector, null, null)); List<JavaFileObject> javaFileObjectList = new ArrayList<>(); javaFileObjectList.add(new JavaSourceObject(fullName, sourceCode)); JavaCompiler.CompilationTask task = this.javaCompiler.getTask(null, javaFileManager, diagnosticCollector, null, null, javaFileObjectList); if (task.call()) { return javaFileManager.getClassLoader(null).loadClass(fullName); } System.out.println(diagnosticCollector.getDiagnostics().get(0).getLineNumber()); System.out.println(diagnosticCollector.getDiagnostics().get(0).getColumnNumber()); System.out.println(diagnosticCollector.getDiagnostics().get(0).getMessage(Locale.ENGLISH)); System.out.println(diagnosticCollector.getDiagnostics().get(0).getSource()); System.out.println(diagnosticCollector.getDiagnostics().get(0).getCode()); return Class.forName(fullName); }}自定义源文件处理
自定义源文件处理，核心方法是getCharContent，返回源码内容，kind=SOURCE
package io.github.kennethfan.compiler;import javax.tools.SimpleJavaFileObject;import java.io.IOException;import java.net.URI;/** * Created by kenneth on 2023/5/28. */class JavaSourceObject extends SimpleJavaFileObject { /** * 类名 */ private final String className; /** * 源代码 */ private final String sourceCode; public JavaSourceObject(String className, String sourceCode) { super(URI.create("String:///" + className.replaceAll("\\.", ".") + Kind.SOURCE.extension), Kind.SOURCE); this.className = className; this.sourceCode = sourceCode; } @Override public CharSequence getCharContent(boolean ignoreEncodingErrors) throws IOException { return this.sourceCode; } public String getClassName() { return className; }}自定义输出文件处理
接下来自定义编译class文件处理，
class JavaClassObject extends SimpleJavaFileObject { private final String className; private final ByteArrayOutputStream byteArrayOutputStream; public JavaClassObject(String className) { super(URI.create("String:///" + className.replaceAll("\\.", "/") + Kind.CLASS.extension), Kind.CLASS); this.className = className; this.byteArrayOutputStream = new ByteArrayOutputStream(); } @Override public OutputStream openOutputStream() throws IOException { return this.byteArrayOutputStream; } public String getClassName() { return className; } public byte[] getBytes() { return this.byteArrayOutputStream.toByteArray(); }}自定义JavaFileManager
接下来实现JavaFileManager，此处继承ForwardingJavaFileManager
package io.github.kennethfan.compiler;import javax.tools.FileObject;import javax.tools.ForwardingJavaFileManager;import javax.tools.JavaFileManager;import javax.tools.JavaFileObject;import java.io.IOException;import java.security.SecureClassLoader;/** * Created by kenneth on 2023/5/28. */public class ClassFileManager extends ForwardingJavaFileManager<JavaFileManager> { private JavaClassObject javaClassObject; public ClassFileManager(JavaFileManager fileManager) { super(fileManager); } @Override public ClassLoader getClassLoader(Location location) { return new SecureClassLoader() { @Override protected Class<?> findClass(String name) throws ClassNotFoundException { byte[] bytes = javaClassObject.getBytes(); return super.defineClass(name, bytes, 0, bytes.length); } }; } @Override public JavaFileObject getJavaFileForOutput(Location location, String className, JavaFileObject.Kind kind, FileObject sibling) throws IOException { this.javaClassObject = new JavaClassObject(className); return this.javaClassObject; }}测试
import io.github.kennethfan.compiler.RuntimeCompiler;import org.junit.Assert;import org.junit.Test;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;public class RuntimeCompilerTest { @Test public void test_static() throws ClassNotFoundException, InvocationTargetException, IllegalAccessException, NoSuchMethodException { String classStream = "public class TestClass {\n" + "\n" + " public int add(int a, int b) {\n" + " return a + b;\n" + " }\n" + "\n" + " public static double pow(double a, double b) {\n" + " return Math.pow(a, b);\n" + " }\n" + "}\n"; Class<?> clazz = new RuntimeCompiler().compileAndLoad("TestClass", classStream); Method staticMethod = clazz.getMethod("pow", double.class, double.class); double a = 2.0d; double b = 3.0d; Assert.assertEquals(8.0d, staticMethod.invoke(null, a, b)); } @Test public void test_normal() throws ClassNotFoundException, InvocationTargetException, IllegalAccessException, NoSuchMethodException, InstantiationException { String classStream = "public class TestClass {\n" + "\n" + " public int add(int a, int b) {\n" + " return a + b;\n" + " }\n" + "\n" + " public static double pow(double a, double b) {\n" + " return Math.pow(a, b);\n" + " }\n" + "}\n"; Class<?> clazz = new RuntimeCompiler().compileAndLoad("TestClass", classStream); Method staticMethod = clazz.getMethod("add", int.class, int.class); Assert.assertEquals(8, staticMethod.invoke(clazz.newInstance(), 5, 3)); }}
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