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[Java教程]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);	}}