com.gitee.huanminabc.utils_common.obj.dynamicbean.DynamicCompiler Maven / Gradle / Ivy
package com.gitee.huanminabc.utils_common.obj.dynamicbean;
import javax.tools.*;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URI;
import java.util.ArrayList;
import java.util.List;
public class DynamicCompiler {
/**
* 动态生成类,内存版, 不会生成类文件,不会生成class文件而是直接编译到内存里
* @param fullClassName 全路径的类名
* @param javaCode java代码
* @return 目标类
*/
public static Class compileToClass(String fullClassName, String javaCode) throws Exception {
JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
DiagnosticCollector diagnostics = new DiagnosticCollector<>();
MyFileManager fileManager = new MyFileManager(compiler.getStandardFileManager(diagnostics, null, null));
List jfiles = new ArrayList<>();
jfiles.add(new MySimpleJavaFileObject(fullClassName, javaCode));
List options = new ArrayList<>();
options.add("-encoding");
options.add("UTF-8");
JavaCompiler.CompilationTask task = compiler.getTask(null, fileManager, diagnostics, options, null, jfiles);
boolean success = task.call();
if (success) {
MyJavaClassFileObject javaClassObject = fileManager.getJavaClassObject();
MyClassLoader dynamicClassLoader = new MyClassLoader();
//加载至内存
return dynamicClassLoader.loadClass(fullClassName, javaClassObject);
} else {
for (Diagnostic diagnostic : diagnostics.getDiagnostics()) {
String error = compileError(diagnostic);
throw new RuntimeException(error);
}
throw new RuntimeException("compile error");
}
}
private static String compileError(Diagnostic diagnostic) {
StringBuilder res = new StringBuilder();
res.append("LineNumber:[").append(diagnostic.getLineNumber()).append("]\n");
res.append("ColumnNumber:[").append(diagnostic.getColumnNumber()).append("]\n");
res.append("Message:[").append(diagnostic.getMessage(null)).append("]\n");
return res.toString();
}
private static class MyClassLoader extends ClassLoader {
public Class loadClass(String fullName, MyJavaClassFileObject javaClassObject) {
byte[] classData = javaClassObject.getBytes();
return this.defineClass(fullName, classData, 0, classData.length);
}
}
private static class MyFileManager extends ForwardingJavaFileManager {
private MyJavaClassFileObject javaClassObject;
protected MyFileManager(StandardJavaFileManager standardJavaFileManager) {
super(standardJavaFileManager);
}
public MyJavaClassFileObject getJavaClassObject(){
return javaClassObject;
}
@Override
public JavaFileObject getJavaFileForOutput(Location location, String className, JavaFileObject.Kind kind, FileObject sibling) {
this.javaClassObject = new MyJavaClassFileObject(className, kind);
return javaClassObject;
}
}
//这里需要重写openOutStream()方法，不输出字节码到文件，而是直接保存在一个输出流中。
private static class MyJavaClassFileObject extends SimpleJavaFileObject {
private final ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
public MyJavaClassFileObject(String name, Kind kind) {
super(URI.create("string:///" + name.replace('.', '/') + kind.extension), kind);
}
public byte[] getBytes() {
return outputStream.toByteArray();
}
//编译时候会调用openOutputStream获取输出流,并写数据
@Override
public OutputStream openOutputStream() throws IOException {
return outputStream;
}
}
private static class MySimpleJavaFileObject extends SimpleJavaFileObject {
private String contents;
private String className;
public MySimpleJavaFileObject(String className, String contents) {
super(URI.create("string:///" + className.replace('.', '/') + Kind.SOURCE.extension), Kind.SOURCE);
this.className = className;
this.contents = contents;
}
@Override
public CharSequence getCharContent(boolean ignoredEncodingErrors) throws IOException {
return contents;
}
}
}