[游戏开发]ASM 添加字段已经生成相对应的get set 方法

1 首先创建一个实体类Student. 代码如下

package com.org.xcyz.asm;

public class Student {
    private int id;
    private String name;
    private boolean sex;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public boolean isSex() {
        return sex;
    }

    public void setSex(boolean sex) {
        this.sex = sex;
    }
}

2 然后准备添加字段age和setAge以及getAge方法

package com.org.xcyz.asm.trans;

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

import static java.nio.file.StandardOpenOption.CREATE;
import static java.nio.file.StandardOpenOption.TRUNCATE_EXISTING;
import static org.objectweb.asm.Opcodes.ACC_PRIVATE;
import static org.objectweb.asm.Opcodes.ACC_PUBLIC;
import static org.objectweb.asm.Opcodes.ALOAD;
import static org.objectweb.asm.Opcodes.GETFIELD;
import static org.objectweb.asm.Opcodes.IRETURN;
import static org.objectweb.asm.Opcodes.PUTFIELD;
import static org.objectweb.asm.Opcodes.RETURN;

public class AddVisitorTransformer1 {
    public static void main(String[] args) throws IOException {
        String className = "com.org.xcyz.asm.Student";
        String classJvmName = className.replace('.', '/');
        ClassReader cr = new ClassReader(className);
        ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES|ClassWriter.COMPUTE_MAXS);
        ClassVisitor classVisitor = new ClassVisitor(Opcodes.ASM9,cw) {
            boolean hasFiled = false;
            @Override
            public FieldVisitor visitField(int access, String name, String descriptor, String signature, Object value) {
                if("age".equals(name) && "I".equals(descriptor))hasFiled=true;
                return super.visitField(access, name, descriptor, signature, value);
            }

            @Override
            public void visitEnd() {
                if (!hasFiled) {
                    FieldVisitor fieldVisitor = cv.visitField(ACC_PRIVATE, "age", "I", null, null);
                    if (fieldVisitor != null) {
                        fieldVisitor.visitEnd();
                    }
                    MethodVisitor setAge = cv.visitMethod(ACC_PUBLIC, "setAge", "(I)V", null, null);
                    if (setAge != null) {
                        setAge.visitCode();
                        setAge.visitVarInsn(ALOAD,0);
                        setAge.visitVarInsn(ALOAD,1);
                        setAge.visitFieldInsn(PUTFIELD,classJvmName,"age","I");
                        setAge.visitInsn(RETURN);
                        setAge.visitEnd();
                    }
                    MethodVisitor getAge = cv.visitMethod(ACC_PUBLIC, "getAge", "()I", null, null);
                    if (getAge != null) {
                        getAge.visitCode();
                        getAge.visitVarInsn(ALOAD,0);
                        getAge.visitFieldInsn(GETFIELD,classJvmName,"age","I");
                        getAge.visitInsn(IRETURN);
                        getAge.visitEnd();
                    }
                }
                super.visitEnd();
            }
        };
        cr.accept(classVisitor,ClassReader.SKIP_DEBUG|ClassReader.SKIP_FRAMES);
        byte[] bytes = cw.toByteArray();
        Files.write(Paths.get("target/classes/"+classJvmName+".class"),bytes,TRUNCATE_EXISTING,CREATE);
    }
}