ASM操作字节码，动态生成Java类class文件

package com.shanhy.demo.asm.hello; import java.io.File; import java.io.FileOutputStream; import java.lang.reflect.Method; import org.objectweb.asm.ClassReader; import org.objectweb.asm.ClassWriter; import org.objectweb.asm.FieldVisitor; import org.objectweb.asm.Label; import org.objectweb.asm.MethodVisitor; import org.objectweb.asm.Opcodes; /** * 通过ASM生成类的字节码 * * @author Administrator * */ public class HelloGeneratorClass implements Opcodes { /** * 使用构造Hello类class字节码<br/> * package中的Hello.java只是代码原型，本例中只供对比用，没有实际使用到这个类。<br/> * ASM代码生成工具使用 bytecode * * @return * @throws Exception * @author SHANHY * @create 2016年2月3日 */ public static byte[] generatorHelloClass() throws Exception { ClassWriter cw = new ClassWriter(0); FieldVisitor fv; MethodVisitor mv; cw.visit(V1_7, ACC_PUBLIC + ACC_SUPER, "com/shanhy/demo/asm/hello/Hello", null, "java/lang/Object", null); cw.visitSource("Hello.java", null); { fv = cw.visitField(ACC_PUBLIC + ACC_FINAL + ACC_STATIC, "FLAG", "Ljava/lang/String;", null, "\u6211\u662f\u5e38\u91cf"); fv.visitEnd(); } { mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null); mv.visitCode(); Label l0 = new Label(); mv.visitLabel(l0); mv.visitVarInsn(ALOAD, 0); mv.visitMethodInsn(INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false); mv.visitInsn(RETURN); Label l1 = new Label(); mv.visitLabel(l1); mv.visitMaxs(1, 1); mv.visitEnd(); } { mv = cw.visitMethod(ACC_PUBLIC, "display", "()V", null, null); mv.visitCode(); Label l0 = new Label(); mv.visitLabel(l0); mv.visitInsn(ICONST_0); mv.visitVarInsn(ISTORE, 1); Label l1 = new Label(); mv.visitLabel(l1); Label l2 = new Label(); mv.visitJumpInsn(GOTO, l2); Label l3 = new Label(); mv.visitLabel(l3); mv.visitFrame(Opcodes.F_APPEND, 1, new Object[] { Opcodes.INTEGER }, 0, null); mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;"); mv.visitLdcInsn(">>>>>>>>>>\u6211\u662f\u5e38\u91cf"); mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false); Label l4 = new Label(); mv.visitLabel(l4); mv.visitIincInsn(1, 1); mv.visitLabel(l2); mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null); mv.visitVarInsn(ILOAD, 1); mv.visitIntInsn(BIPUSH, 8); mv.visitJumpInsn(IF_ICMPLT, l3); Label l5 = new Label(); mv.visitLabel(l5); mv.visitInsn(RETURN); Label l6 = new Label(); mv.visitLabel(l6); mv.visitMaxs(2, 2); mv.visitEnd(); } { mv = cw.visitMethod(ACC_PUBLIC, "testList", "()Ljava/util/List;", "()Ljava/util/List<Ljava/lang/String;>;", null); mv.visitCode(); Label l0 = new Label(); mv.visitLabel(l0); mv.visitTypeInsn(NEW, "java/util/ArrayList"); mv.visitInsn(DUP); mv.visitMethodInsn(INVOKESPECIAL, "java/util/ArrayList", "<init>", "()V", false); mv.visitVarInsn(ASTORE, 1); Label l1 = new Label(); mv.visitLabel(l1); mv.visitVarInsn(ALOAD, 1); mv.visitLdcInsn("Tome"); mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true); mv.visitInsn(POP); Label l2 = new Label(); mv.visitLabel(l2); mv.visitVarInsn(ALOAD, 1); mv.visitLdcInsn("Jack"); mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true); mv.visitInsn(POP); Label l3 = new Label(); mv.visitLabel(l3); mv.visitVarInsn(ALOAD, 1); mv.visitLdcInsn("Lily"); mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true); mv.visitInsn(POP); Label l4 = new Label(); mv.visitLabel(l4); mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;"); mv.visitTypeInsn(NEW, "java/lang/StringBuilder"); mv.visitInsn(DUP); mv.visitLdcInsn(">>>>>>>>>>testList > list.size = "); mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "(Ljava/lang/String;)V", false); mv.visitVarInsn(ALOAD, 1); mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "size", "()I", true); mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;", false); mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false); mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false); Label l5 = new Label(); mv.visitLabel(l5); mv.visitVarInsn(ALOAD, 1); mv.visitInsn(ARETURN); Label l6 = new Label(); mv.visitLabel(l6); mv.visitMaxs(4, 2); mv.visitEnd(); } { mv = cw.visitMethod(ACC_PUBLIC + ACC_VARARGS, "testMapList", "(Z[Ljava/util/Map;)Ljava/util/List;", "(Z[Ljava/util/Map<Ljava/lang/String;Ljava/lang/String;>;)Ljava/util/List<Ljava/util/Map<Ljava/lang/String;Ljava/lang/String;>;>;", null); mv.visitCode(); Label l0 = new Label(); mv.visitLabel(l0); mv.visitTypeInsn(NEW, "java/util/ArrayList"); mv.visitInsn(DUP); mv.visitMethodInsn(INVOKESPECIAL, "java/util/ArrayList", "<init>", "()V", false); mv.visitVarInsn(ASTORE, 3); Label l1 = new Label(); mv.visitLabel(l1); mv.visitVarInsn(ILOAD, 1); Label l2 = new Label(); mv.visitJumpInsn(IFEQ, l2); Label l3 = new Label(); mv.visitLabel(l3); mv.visitVarInsn(ALOAD, 2); mv.visitInsn(DUP); mv.visitVarInsn(ASTORE, 7); mv.visitInsn(ARRAYLENGTH); mv.visitVarInsn(ISTORE, 6); mv.visitInsn(ICONST_0); mv.visitVarInsn(ISTORE, 5); Label l4 = new Label(); mv.visitJumpInsn(GOTO, l4); Label l5 = new Label(); mv.visitLabel(l5); mv.visitFrame(Opcodes.F_FULL, 8, new Object[] { "com/shanhy/demo/asm/hello/Hello", Opcodes.INTEGER, "[Ljava/util/Map;", "java/util/List", Opcodes.TOP, Opcodes.INTEGER, Opcodes.INTEGER, "[Ljava/util/Map;" }, 0, new Object[] {}); mv.visitVarInsn(ALOAD, 7); mv.visitVarInsn(ILOAD, 5); mv.visitInsn(AALOAD); mv.visitVarInsn(ASTORE, 4); Label l6 = new Label(); mv.visitLabel(l6); mv.visitVarInsn(ALOAD, 3); mv.visitVarInsn(ALOAD, 4); mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "add", "(Ljava/lang/Object;)Z", true); mv.visitInsn(POP); Label l7 = new Label(); mv.visitLabel(l7); mv.visitIincInsn(5, 1); mv.visitLabel(l4); mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null); mv.visitVarInsn(ILOAD, 5); mv.visitVarInsn(ILOAD, 6); mv.visitJumpInsn(IF_ICMPLT, l5); mv.visitLabel(l2); mv.visitFrame(Opcodes.F_FULL, 4, new Object[] { "com/shanhy/demo/asm/hello/Hello", Opcodes.INTEGER, "[Ljava/util/Map;", "java/util/List" }, 0, new Object[] {}); mv.visitFieldInsn(GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;"); mv.visitTypeInsn(NEW, "java/lang/StringBuilder"); mv.visitInsn(DUP); mv.visitLdcInsn(">>>>>>>>>>testMapList > list.size = "); mv.visitMethodInsn(INVOKESPECIAL, "java/lang/StringBuilder", "<init>", "(Ljava/lang/String;)V", false); mv.visitVarInsn(ALOAD, 3); mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "size", "()I", true); mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "append", "(I)Ljava/lang/StringBuilder;", false); mv.visitMethodInsn(INVOKEVIRTUAL, "java/lang/StringBuilder", "toString", "()Ljava/lang/String;", false); mv.visitMethodInsn(INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false); Label l8 = new Label(); mv.visitLabel(l8); mv.visitVarInsn(ALOAD, 3); mv.visitInsn(ARETURN); Label l9 = new Label(); mv.visitLabel(l9); mv.visitMaxs(4, 8); mv.visitEnd(); } cw.visitEnd(); return cw.toBy