java反射常用类

Posted 2021-01-01 你真的好美

1. 测试实体类

public class TestClass {

    public String classInfo;

    public String getClassInfo() {
        return classInfo;
    }

    public TestClass(String classInfo) {
        this.classInfo = classInfo;
        System.out.println("invoke this param classInfo constructor.");
    }

    public TestClass()
    {
        System.out.println("invoke this default constructor.");
    }
    public void setClassInfo(String classInfo) {
        this.classInfo = classInfo;
    }

    static {
        System.out.println("init first class.");
    }

    public void showinfo()
    {
        System.out.println("this is default show info method.");
    }

    public void showinfo(String info)
    {
        System.out.println("this is have param method.");
        System.out.println("param context:"+info);
    }



}

1. 　　测试实现类

import org.junit.Test;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

public class getClassInfoTest {
    @Test
    public void testDemo() throws Exception
    {
        /**
         * 1.实现反射的第一步：获取对象的类型信息，java中指存放类型信息的.class文件
         * 2.在这里是获取对象的所有构造方法.
         * 3.找到需要的构造方法.
         * 4.调用指定构造方法,创建对象.
         */
        Class clazz=Class.forName("TestClass");
        /**
         * 获取构造方法
         * 调用newInstance(...) 相当于 new TestClass(...)
         */
        Constructor[] constructors=clazz.getConstructors();
        System.out.println("constructor item:"+‘
‘);
        arrayToStringItem(constructors);
        Object test=constructors[0].newInstance();
        Object test2=constructors[1].newInstance("hello");

        /**
         * 获取属性
         */
        Field[] fields=clazz.getFields();
        System.out.println("field item:"+‘
‘);
        arrayToStringItem(fields);
        Field field=fields[0];
        System.out.println("field name:"+field.getName());
        System.out.println("get dafault constructor field value:"+field.get(test));
        System.out.println("get have param constructor field value:"+field.get(test2));

        /**
         * 获取方法
         */
        Method[] methods=clazz.getMethods();
        System.out.println("method item:"+‘
‘);
        arrayToStringItem(methods);
        System.out.println("invoke "+methods[0].getName()+" get return value:"+methods[0].invoke(test2));
    }

    public void arrayToStringItem(Object[] args)
    {
        for (Object c:args)
        {
            System.out.println(c);
        }
    }
}