5.java动态代理、反射

1.java动态代理、反射(IDEA导入JUnit4)

1.1.反射

　　通过反射的方式可以获取class对象中的属性、方法、构造函数等

1.2.反射代码

import java.io.Serializable;

public class Person implements Serializable,TestInterface{
    private Long id;
    public String name;

    public Person() {
        this.id = 100L;
        this.name = "afsdfasd";
    }

    public Person(Long id, String name) {
        //super();
        this.id = id;
        this.name = name;
    }
    
    
    public Person(Long id) {
        super();
        this.id = id;
    }
    @SuppressWarnings("unused")
    private Person(String name) {
        super();
        this.name = name+"=======";
    }

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String toString() {
        return "Person [>;
    }
    private String getSomeThing() {
        return "sdsadasdsasd";
    }
    
    private void testPrivate(){
        System.out.println("this is a private method");
    }
}
package cn.itcast_04_reflect;

import java.io.Serializable;

public class Person implements Serializable,TestInterface{
    private Long id;
    public String name;

    public Person() {
        this.id = 100L;
        this.name = "afsdfasd";
    }

    public Person(Long id, String name) {
       //super();
        this.id = id;
        this.name = name;
    }
    
    
    public Person(Long id) {
        super();
        this.id = id;
    }
    @SuppressWarnings("unused")
    private Person(String name) {
        super();
        this.name = name+"=======";
    }

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public String toString() {
        return "Person [>;
    }
    private String getSomeThing() {
        return "sdsadasdsasd";
    }
    
    private void testPrivate(){
        System.out.println("this is a private method");
    }
}

package cn.itcast_04_reflect;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
import org.junit.Before;
import org.junit.Test;

public class MyReflect {
    public String className = null;
    @SuppressWarnings("rawtypes")
    public Class personClass = null;
    /**
     * 反射Person类
     * @throws Exception
     */
    @Before
    public void init() throws Exception {
        className = "cn.itcast_04_reflect.Person";
        personClass = Class.forName(className);
    }
    /**
     *获取某个class文件对象
     */
    @Test
    public void getClassName() throws Exception {
        System.out.println(personClass);
    }
    /**
     *获取某个class文件对象的另一种方式
     */
    @Test
    public void getClassName2() throws Exception {
        System.out.println(Person.class);
    }
    /**
     *创建一个class文件表示的实例对象，底层会调用空参数的构造方法
     */
    @Test
    public void getNewInstance() throws Exception {
        System.out.println(personClass.newInstance());
    }
    /**
     *获取非私有的构造函数
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    @Test
    public void getPublicConstructor() throws Exception {
        Constructor  constructor  = personClass.getConstructor(Long.class,String.class);
        Person person = (Person)constructor.newInstance(100L,"zhangsan");
        System.out.println(person.getId());
        System.out.println(person.getName());
    }
    /**
     *获得私有的构造函数
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    @Test
    public void getPrivateConstructor() throws Exception {
        Constructor con = personClass.getDeclaredConstructor(String.class);
        con.setAccessible(true);//强制取消Java的权限检测
        Person person2 = (Person)con.newInstance("zhangsan");
        System.out.println("**"+person2.getName());
    }
    /**
     *访问非私有的成员变量
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    @Test
    public void getNotPrivateField() throws Exception {
        Constructor  constructor  = personClass.getConstructor(Long.class,String.class);
        Object obj = constructor.newInstance(100L,"zhangsan");
        
        Field field = personClass.getField("name");
        field.set(obj, "lisi");
        System.out.println(field.get(obj));
    }
    /**
     *访问私有的成员变量
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    @Test
    public void getPrivateField() throws Exception {
        Constructor  constructor  = personClass.getConstructor(Long.class);
        Object obj = constructor.newInstance(100L);
        
        Field field2 = personClass.getDeclaredField("id");
        field2.setAccessible(true);//强制取消Java的权限检测
        field2.set(obj,10000L);
        System.out.println(field2.get(obj));
    }
    /**
     *获取非私有的成员函数
     */
    @SuppressWarnings({ "unchecked" })
    @Test
    public void getNotPrivateMethod() throws Exception {
        System.out.println(personClass.getMethod("toString"));
        
        Object obj = personClass.newInstance();//获取空参的构造函数
        Method toStringMethod = personClass.getMethod("toString");
        Object object = toStringMethod.invoke(obj);
        System.out.println(object);
    }
    /**
     *获取私有的成员函数
     */
    @SuppressWarnings("unchecked")
    @Test
    public void getPrivateMethod() throws Exception {
        Object obj = personClass.newInstance();//获取空参的构造函数
        Method method = personClass.getDeclaredMethod("getSomeThing");
        method.setAccessible(true);
        Object value = method.invoke(obj);
        System.out.println(value);

    }
    @Test
    public void otherMethod() throws Exception {
        //当前加载这个class文件的那个类加载器对象
        System.out.println(personClass.getClassLoader());
        //获取某个类实现的所有接口
        Class[] interfaces = personClass.getInterfaces();
        for (Class class1 : interfaces) {
            System.out.println(class1);
        }
        //反射当前这个类的直接父类
        System.out.println(personClass.getGenericSuperclass());
        /**
         * getResourceAsStream这个方法可以获取到一个输入流，这个输入流会关联到name所表示的那个文件上。
         */
        //path 不以’/'开头时默认是从此类所在的包下取资源，以’/'开头则是从ClassPath根下获取。其只是通过path构造一个绝对路径，最终还是由ClassLoader获取资源。
        System.out.println(personClass.getResourceAsStream("/log4j.properties"));
        System.out.println(personClass.getResourceAsStream("log4j.properties"));
        
        //判断当前的Class对象表示是否是数组
        System.out.println(personClass.isArray());
        System.out.println(new String[3].getClass().isArray());
        
        //判断当前的Class对象表示是否是枚举类
        System.out.println(personClass.isEnum());
        System.out.println(Class.forName("cn.itcast_04_reflect.City").isEnum());
        
        //判断当前的Class对象表示是否是接口
        System.out.println(personClass.isInterface());
        System.out.println(Class.forName("cn.itcast_04_reflect.TestInterface").isInterface());
    }
}

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