Java 反射机制 之 简单模拟反编译

Java 反射机制 之 简单模拟反编译

　　如何解决参数名是 arg0... 之类，参考: Java8获取参数名及Idea/Eclipse/Maven配置 , 当然如果去反编译 Java 自带的类 比如 String 得到的参数还是 arg0... 。
　　为什么？因为反射机制是对 字节码文件（.class 结尾）操作。而我们使用 String 之类的类是已经编译好的，看 jre 压缩包就能发现。
　　

源码（带注释）：

    public static void main(String[] args) throws ClassNotFoundException {
        StringBuilder sb = new StringBuilder();

        //
        Class<?> reflectClass = Class.forName("com.hjx.反射.Field反编译.Person");

        // reflectClass.getModifiers() 得到是特定 数字
        // 需要用 Modifier.toString() 转为特定 修饰符
        sb.append(Modifier.toString(reflectClass.getModifiers()));
        sb.append(" class ");
        // getName() 获取全称  如：java.lang.String
        // getSimpleName() 获取简称  如：String
        sb.append(reflectClass.getSimpleName());
        sb.append(" {");

        // 注意是 getDeclaredFields 而不是 getFields
        // 因为 getFields 方法只能获取所有公开的属性
        Field[] fields = reflectClass.getDeclaredFields();
        for (Field field : fields) {
            sb.append("\n\t");
            sb.append(Modifier.toString(field.getModifiers()));
            sb.append(" ");
            sb.append(field.getType().getSimpleName());
            sb.append(" ");
            sb.append(field.getName());
            sb.append(";");
        }

        sb.append("\n");


        // 添加类的构造方法
        Constructor[] constructors = reflectClass.getDeclaredConstructors();
        for (Constructor constructor : constructors) {
            sb.append("\n\t");
            sb.append(Modifier.toString(constructor.getModifiers()));
            sb.append(" ");
            sb.append(reflectClass.getSimpleName());
            sb.append(" (");
            // 参数类型  数组
            Class<?>[] types = constructor.getParameterTypes();
            // 参数名  数组
            Parameter[] parameters = constructor.getParameters();

            appendParam(sb, types, parameters);

            sb.append(")");
            sb.append("{}");
        }

        // 添加类的方法
        // getDeclaredMethods  getMethods 区别同上
        Method[] methods = reflectClass.getDeclaredMethods();
        for (Method method : methods) {
            sb.append("\n\t");
            sb.append(Modifier.toString(method.getModifiers()));
            sb.append(" ");
            // getReturnType() 返回类型
            sb.append(method.getReturnType().getSimpleName());
            sb.append(" ");
            sb.append(method.getName());
            sb.append(" (");

            Class<?>[] types = method.getParameterTypes();
            Parameter[] parameters = method.getParameters();

            appendParam(sb, types, parameters);

            sb.append(")");
            sb.append("{}");
        }

        sb.append("\n}");
        System.out.println(sb.toString());
    }

    // 添加方法参数
    private static void appendParam(StringBuilder sb,Class<?>[] types,Parameter[] parameters){
        int num = 0;
        for (int i = 0; i < types.length; i++) {
            sb.append(types[i].getSimpleName());
            sb.append(" ");
            sb.append(parameters[i].getName());
            sb.append(",");
            num++;
        }
        // 删除多余的 ","
        if (num > 0){
            sb.deleteCharAt(sb.length()-1);
        }
    }

Person类 源码：

public class Person {

    public void test(String str, int i, char c){}

    private String name;
    private int age;
    private String address;
    private String remark;

    public Person() {
    }
    public Person(String name, int age, String address, String remark) {
        this.name = name;
        this.age = age;
        this.address = address;
        this.remark = remark;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getRemark() {
        return remark;
    }

    public void setRemark(String remark) {
        this.remark = remark;
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                ", address='" + address + '\'' +
                ", remark='" + remark + '\'' +
                '}';
    }

    private static void test(String[] strs,Object o){

    }
}

运行结果：

public class Person {
	private String name;
	private int age;
	private String address;
	private String remark;

	public Person (String name,int age,String address,String remark){}
	public Person (){}
	public String toString (){}
	public String getAddress (){}
	public String getName (){}
	public void setName (String name){}
	public void test (String str,int i,char c){}
	public void setAge (int age){}
	public void setAddress (String address){}
	public void setRemark (String remark){}
	public String getRemark (){}
	public int getAge (){}
}