chapter.java.reflect.xml

<?xml version="1.0" encoding="UTF-8"?>
<chapter id="index"><?dbhtml dir="reflect" ?>
	<title>Reflection 反射</title>
	<screen>
this.getClass().getName() //当前Class名字
Thread.currentThread().getStackTrace()[1].getMethodName()); //当前方法名
	</screen>
		<section>
			<title>获得所有变量</title>
			<programlisting>
			<![CDATA[
			
	Field[] fields = objClass.getFields();
	for (Field field : fields) {
		System.out.println(field.getName());
	}
			]]>
			</programlisting>
			<para>注意：只能去除 public变量</para>
		</section>

		<section>
			<title>批量赋值</title>
		</section>
		
	<section>
		<title>方法操作</title>
		<para>JAVA反射调用方法的步骤有三步</para>
		<screen>
得到要调用类的class
得到要调用的类中的方法(Method)
方法调用(invoke)
		</screen>
		<section>
			<title>获得所有方法</title>
			<programlisting>
			<![CDATA[
	Class<?> objClass = a.getClass();
	Method[] methods =  objClass.getDeclaredMethods();
	for (Method method : methods) {
		System.out.println(method);
	}			
			]]>
			</programlisting>
		</section>
		<section>
			<title>set/get 方法</title>
			<programlisting>
			<![CDATA[
package cn.netkiller.reflect;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class Member {
	public String name;
	private int age;

	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;
	}

	@Override
	public String toString() {
		return "ClassA [name=" + name + ", age=" + age + "]";
	}

	public Member() {
		// TODO Auto-generated constructor stub
	}

	public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchMethodException, SecurityException, IllegalArgumentException, InvocationTargetException {
		Class<?> cls = Class.forName("cn.netkiller.reflect.Member");
		Object member = cls.newInstance();
		Method setMethod = cls.getDeclaredMethod("setAge", int.class);
		setMethod.invoke(member, 15);

		Method getMethod = cls.getDeclaredMethod("getAge");
		System.out.println(getMethod.invoke(member));

	}

}
			]]>
			</programlisting>
			<para>下面做一个稍微复杂点的例子，ClassB继承ClassA，取出ClassA的成员变量赋值到ClassA。</para>
			<screen>
			<![CDATA[
package cn.netkiller.reflect;

public class ClassA {
	public String name;
	private int age;

	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 ClassA() {
		// TODO Auto-generated constructor stub
	}

	@Override
	public String toString() {
		return "ClassA [name=" + name + ", age=" + age + "]";
	}
}

package cn.netkiller.reflect;

public class ClassB extends ClassA{

	public ClassB() {
		// TODO Auto-generated constructor stub
	}
	private String address;

	public String getAddress() {
		return address;
	}

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

	@Override
	public String toString() {
		return "ClassB [address=" + address + "]";
	}
	
}


package cn.netkiller.reflect;

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

public class ReflectionTest {

	public ReflectionTest() {
		// TODO Auto-generated constructor stub
	}

	public void testSetMethod() throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, InstantiationException {

		// ClassA a = new ClassA();

		ClassB b = new ClassB();
		b.setAddress("Shenzhen");

		Class<ClassA> classA = ClassA.class;
		ClassA a = classA.newInstance();
		a.setName("Neo");
		a.setAge(30);

		System.out.println(classA.getDeclaredMethod("getAge").invoke(a));

		Method m = classA.getDeclaredMethod("setAge", int.class);
		m.setAccessible(true); // 因为写成private 所以这里必须设置
		m.invoke(b, 26);

		System.out.println(a.toString());
		System.out.println(b.toString());

		System.out.println(b.getName());
		System.out.println(b.getAge());
	}

	public static void main(String[] args) throws InvocationTargetException {

		ReflectionTest rt = new ReflectionTest();
		try {
			rt.testSetMethod();
			
		} catch (NoSuchMethodException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (SecurityException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalArgumentException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		
	}

}



			]]>
			</screen>
			<para>set 方法</para>
			<programlisting>
			<![CDATA[
System.out.println(classA.getDeclaredMethod("getAge").invoke(a));	
			]]>
			</programlisting>
			<para>get 方法</para>
			<programlisting>
			<![CDATA[
	Method m = classA.getDeclaredMethod("setAge", int.class);
	m.setAccessible(true);	//因为写成private 所以这里必须设置
	m.invoke(b, 26);	
			]]>
			</programlisting>
		</section>
		<section>
			<title>static 方法调用</title>
			<para></para>
			<programlisting>
			<![CDATA[
Class cls = Class.forName("cn.netkiller.reflect.Student");
Method setMethod = cls.getDeclaredMethod("setAge",int.class);
setMethod.invoke(cls.newInstance(), 15);
			]]>
			</programlisting>
			<para>static 方法调用时，不必得实例化对象</para>
			<programlisting>
			<![CDATA[
Class cls = Class.forName("cn.netkiller.reflect.Student");
Method staticMethod = cls.getDeclaredMethod("setAge",int.class);
staticMethod.invoke(cls,20); //这里不需要newInstance
			]]>
			</programlisting>
		</section>
	</section>
	<section>
		<title>完成的例子</title>
		<programlisting>
		<![CDATA[
package cn.netkiller;

import java.lang.reflect.Field;


public class Test {
    static class MyClass {
        public String var1 = "Hello";
        public int var2 = 123;
        public double var3;
        public String var4;
    }

    public static void main(String[] args) throws IllegalAccessException, NoSuchFieldException {
        MyClass obj = new MyClass();

//        obj.var4 = "World";

        Class<? extends MyClass> clazz = obj.getClass();
        Field field1 = clazz.getDeclaredField("var4");
        field1.setAccessible(true); // 设置可访问性
        field1.set(obj, "Neo"); // 设置值


        Field[] fields = obj.getClass().getDeclaredFields();
        for (Field field : fields) {
            field.setAccessible(true); // 设置为可访问
            if (field.get(obj) != null) {
                System.out.println(field.getName() + " = " + field.get(obj));
            }
        }
    }
}
		
		]]>
		</programlisting>
		<programlisting>
		<![CDATA[
package cn.netkiller;

import lombok.Data;

import java.lang.reflect.Field;


public class Test {
    @Data
    static class MyClass {
        public String var1;
        public Integer var2;
        public Double var3;
        public String var4;
    }

    public static Object setValue(Object obj, Object target) throws IllegalAccessException, NoSuchFieldException {
        Field[] fields = obj.getClass().getDeclaredFields();
        Class<?> clazz = target.getClass();
        for (Field field : fields) {
            field.setAccessible(true); // 设置为可访问
            System.out.println(field.getName() + " = " + field.get(obj));
            if (field.get(obj) != null) {

                Field field1 = clazz.getDeclaredField(field.getName());
                field1.setAccessible(true); // 设置可访问性
                field1.set(target, field.get(obj)); // 设置值
            }
        }
        System.out.println(target);
        return target;
    }

    public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
        MyClass obj = new MyClass();
        obj.var1 = "Hello";
        obj.var4 = "World";
        MyClass target = new MyClass();
        setValue(obj, target);
    }
}		
		]]>
		</programlisting>
	</section>
</chapter>