Java之反射的应用

 

package com.zheges;

import java.util.Date;

public class Customer {//JavaBean 对象
	private String name;
	private int password;
	public String present = "God";
	private Date date;

	@Override
	public String toString() {
		return "Customer [name=" + name + ", password=" + password
				+ ", present=" + present + ", date=" + date + "]";
	}

	public String getPresent() {
		return present;
	}
	public void setPresent(String present) {
		this.present = present;
	}
	public String getName() {
		return name;
	}
	public Date getDate() {
		return date;
	}
	public void setDate(Date date) {
		this.date = date;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getPassword() {
		return password;
	}
	public void setPassword(int password) {
		this.password = password;
	}
	public String getAB(){
		return "AB";
	}
}

 

package com.zheges;

import static org.junit.Assert.assertEquals;//静态导入Assert所有静态方法
import java.lang.reflect.Field;
import org.junit.Before;
import org.junit.Test;

/**
* 项目名称：Reflection
* 类名称：FirDemo
* 类描述：反射的基本应用
* 创建人：ZHe
* 创建时间：2015年8月29日 下午5:01:43
* 修改人：ZHe
* 修改时间：2015年8月29日 下午5:01:43
 */
public class FirDemo {

	private Class<?> clazz;//类的字节码
	private Customer customer = new Customer();

	/**
	 * 1.加载类，并且获得类的字节码
	 * @throws ClassNotFoundException
	 */
	@Before
	public void getClassLoader() throws ClassNotFoundException {
		//1.使用Class的静态方法加载
		clazz = Class.forName("com.zheges.Customer");//注意：这里要使用类的全名
		//2.通过类对象获得其字节码
		clazz = new Customer().getClass();
		//3.通过类的静态属性获得
		clazz = Customer.class;

		assertEquals("com.zheges.Customer",clazz.getName());
	}

	/**
	 * 2.获得类的字段(注意：不等同于属性，属性由getter来确定！)
	 * @throws SecurityException
	 * @throws NoSuchFieldException
	 * @throws IllegalAccessException
	 * @throws IllegalArgumentException
	 */
	@Test
	public void getClassProperties() throws NoSuchFieldException, SecurityException, IllegalArgumentException, IllegalAccessException{

		//1.获得私有字段及其类型
		Field field = clazz.getDeclaredField("name");
		Class<?> type = field.getType();
		assertEquals(String.class, type);

		//2.获得公有字段及其类型
		Field field1 = clazz.getField("present");
		Class<?> type1 = field1.getType();
		assertEquals(String.class, type1);

		//3.true if this object is the same as the obj argument; false otherwise.
		assertEquals(true, field.equals(clazz.getDeclaredField("name")));

		//4.设置某个对象上该字段的值
		field.setAccessible(true);//该字段是私有的,需要设置setAccessible
		field.set(customer,"ZheGes");

		field1.set(customer, "Nor");

		assertEquals(customer.getName(), "ZheGes");
		assertEquals(customer.getPresent(), "Nor");

		//5.获取某个对象上该字段的值
		assertEquals(field.get(customer), "ZheGes");//前提是该私有变量设置了Accessible
		assertEquals(field1.get(customer), "Nor");
	}
}

 

package com.zheges;

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import static org.junit.Assert.*;

import org.junit.Ignore;
import org.junit.Test;

/**
* 项目名称：Reflection
* 类名称：SecDemo
* 类描述：反射高级应用：内省
* 创建人：ZHe
* 创建时间：2015年8月29日 下午5:03:02
* 修改人：ZHe
* 修改时间：2015年8月29日 下午5:03:02
 */
public class SecDemo {
	//内省：通过反射的方式访问javabean的技术
	//JavaBean:1.必须有无参的构造函数 2.属性必须私有（属性数目由get数目来定，并非由字段来定！）3.提供标准的getter和setter

	//1.打印Customer的所有属性(包含Object的属性)
	/*result:
			    AB-----Customer getter
				class ----Object getter,getClass---->这个方法是继承Object的
				date
				name
				password
				present*/
	@Ignore
	public void getProperties() throws IntrospectionException{
		BeanInfo beanInfo = Introspector.getBeanInfo(Customer.class);
		PropertyDescriptor [] propertyDescriptors = beanInfo.getPropertyDescriptors();
		for (PropertyDescriptor propertyDescriptor : propertyDescriptors) {
			System.out.println(propertyDescriptor.getName());
		}
	}

	//2.打印Customer的所有属性（不包含Object的属性）
	@Ignore
	public void getOwnProperties() throws IntrospectionException{
		BeanInfo beanInfo = Introspector.getBeanInfo(Customer.class,Object.class);
		PropertyDescriptor [] propertyDescriptors = beanInfo.getPropertyDescriptors();
		for (PropertyDescriptor propertyDescriptor : propertyDescriptors) {
			System.out.println(propertyDescriptor.getName());
		}
	}

	//3.操作JavaBean的指定属性
	@Test
	public void actProperty() throws IntrospectionException, IllegalAccessException, IllegalArgumentException, InvocationTargetException{
		Customer customer = new Customer();

		PropertyDescriptor propertyDescriptor = new PropertyDescriptor("name", Customer.class);
		Method method = propertyDescriptor.getWriteMethod();
		method.invoke(customer, "zheGes");

		Method method2 = propertyDescriptor.getReadMethod();
		System.out.println(method2.invoke(customer, null));
	}

	//4.获得当前操作属性的类型
	@Ignore
	public void getPropertyType() throws IntrospectionException{
		PropertyDescriptor propertyDescriptor = new PropertyDescriptor("name", Customer.class);
		assertEquals(String.class, propertyDescriptor.getPropertyType());
	}

}

 

package com.zheges;

import static org.junit.Assert.assertTrue;

import java.lang.reflect.InvocationTargetException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import org.apache.commons.beanutils.BeanUtils;
import org.apache.commons.beanutils.ConversionException;
import org.apache.commons.beanutils.ConvertUtils;
import org.apache.commons.beanutils.Converter;
import org.apache.commons.beanutils.locale.converters.DateLocaleConverter;
import org.junit.Ignore;
import org.junit.Test;

/**
* 项目名称：Reflection
* 类名称：ThrDemo
* 类描述：反射的高级应用2：BeanUtils
* 创建人：ZHe
* 创建时间：2015年8月29日 下午5:50:20
* 修改人：ZHe
* 修改时间：2015年8月29日 下午5:50:20
 */
public class ThrDemo {
	private Customer customer = new Customer();

	//1.BeanUtils操作属性
	@Ignore
	public void actProperty() throws IllegalAccessException, InvocationTargetException, Exception{

		BeanUtils.setProperty(customer, "name", "ZHeGes");
		BeanUtils.setProperty(customer, "password", "404");//发生了String转int，但这种转换只支持8种基础类型！

		System.out.println(BeanUtils.getProperty(customer, "name")+" "+
				BeanUtils.getProperty(customer, "password"));
	}

	//2.对于非基础类型的转换，则要给BeanUtils注册转换器
	@Ignore
	public void registConver() throws Exception {

		//注册一个日期转换器,Converter接口，使用匿名内部类实现
		ConvertUtils.register(new Converter(){
			@Override
			public Object convert(Class type, Object value) {
				if(null == value){
					return null;
				}
				if( !(value instanceof String)){
					throw new ConversionException("只支持String类型的转换");
				}
				String str = (String)value;
				SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");

				try {
					return simpleDateFormat.parse(str);
				} catch (ParseException e) {
					throw new RuntimeException(e);//异常链不能断！
				}
			}

		}, Date.class);

		BeanUtils.setProperty(customer, "date", "1992-3-18");
		//The property's value, converted to a String
		System.out.println(BeanUtils.getProperty(customer, "date"));
		System.out.println(customer.getDate().toLocaleString());
	}

	//3.使用Apach公司提供的日期转换器
	@Ignore
	public void registConver2() throws Exception{
		ConvertUtils.register(new DateLocaleConverter(), Date.class);
		BeanUtils.setProperty(customer, "date", "1992-3-18");
		System.out.println(customer.getDate().toLocaleString());
	}

	//4.使用BeanUtils将Map对象填充到JavaBean
	@Ignore
	public void usePopulate() throws Exception{
		Map map = new HashMap<>();
		map.put("name", "ZheGes");
		map.put("password", "123");
		map.put("date", "1992-2-1");

		//日期转换器
		ConvertUtils.register(new DateLocaleConverter(), Date.class);

		BeanUtils.populate(customer, map);
		System.out.println(customer);
	}

	@Test
	public void test(){
		String str = "hell";
		String str1 = str;
		str = "wofl";
		System.out.println(str+" "+str1);
	}

	@Ignore
	public void test2(){
		Class<String> t1 = String.class;
		//Class<String> t2 = Date.class;      false：加了类型约束，必须是类String的字节码，否则报错！
		Class t3 = String.class;
		assertTrue(t1 == t3);
	}
}