Spring安装基本属性的原理分析与代码实现

Spring装配基本属性的原理分析与代码实现

首先，做一个配置属性的基本测试。修改beans.xml,使引用外部类变成内部bean属性：

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

?????? xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

?????? xsi:schemaLocation="http://www.springframework.org/schema/beans

?????????? http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

???????? <bean id="peopleDao" style="text-align: left; margin: 0cm 0cm 3.75pt; background: #fafafa; padding: 0cm;">???????? <bean id="peopleService" style="text-align: left; margin: 0cm 0cm 3.75pt; background: #fafafa; padding: 0cm;">???????? ???????? <property name="peopleDao" ref=” peopleDao”/>

???????? ????????

???????? </bean>

</beans>

? 测试：

public class Test {

??? public static void main(String[] args) {

??????? //IOC容器实例化

??????? ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("beans.xml");

??????? PeopleService peopleService = (PeopleService) ac.getBean("peopleService");

??????? peopleService.save();

??? }

}

? ??结果正常！能够引用得到（这不是废话么）?

?? 使用ref，ref所指向的bean可以被多个bean引用；ref依赖对象将作为一个属性被注入。

Spring是如何实现装配基本属性的呢？下面用源码模拟实现之：

1、在xml配置文件中增加属性：

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

?????? xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

?????? xsi:schemaLocation="http://www.springframework.org/schema/beans

?????????? http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">

???????? <!--? <bean id="peopleDao" style="text-align: left; margin: 0cm 0cm 3.75pt; background: #fafafa; padding: 0cm;">???????? <bean id="peopleService" style="text-align: left; margin: 0cm 0cm 3.75pt; background: #fafafa; padding: 0cm;">???????? ?????????? <property name="peopleDao" ref="com.wxy.dao.impl.PeopleDaoBean"/>

???????? ?????????? <property name="name" value="wxy"/>

???????? ?????????? <property name="id" value="218"/>

???????? </bean>

</beans>

????

2、在属性Bean：PorpertyDefinition中定义相应的属性，用来存放xml文件中定义的属性：

package com.wxy.bean;

/**

*?? 存放bean的property属性

*?? @creator??????????? xiaoyu.wang??

*?? @create-time???? 2011-8-10?? 下午04:40:07??

*?? @revision????????? $Id

public class PropertyDefinition {

? ??private String name; //属性名

??? private String ref;? //属性依赖对象

??? private String value;

??? /**

???? * @return the name

???? */

??? public String getName() {

??????? return name;

??? }

??? /**

???? * @param name the name to set

???? */

??? public void setName(String name) {

??????? this.name = name;

??? }

??? /**

???? * @return the ref

???? */

??? public String getRef() {

??????? return ref;

??? }

??? /**

???? * @param ref the ref to set

???? */

??? public void setRef(String ref) {

?????? ?this.ref = ref;

??? }

??? public PropertyDefinition(String name, String ref, String value) {

??????? super();

??????? this.name = name;

??????? this.ref = ref;

??????? this.value = value;

??? }

??? /**

???? * @return the value

???? */

??? public String getValue() {

??????? return value;

??? }

??? /**

???? * @param value the value to set

???? */

??? public void setValue(String value) {

??????? this.value = value;

??? }

??? /* (non-Javadoc)

???? * @see java.lang.Object#toString()

???? */

? ??@Override

??? public String toString() {

??????? return "PropertyDefinition [name=" + name + ", ref=" + ref + ", value=" + value + "]";

??? }

}

???

3、修改PeopelServiceBean ，添加相对应的属性：

?public class PeopleServiceBean implements PeopleService {

??? private PeopleDao peopleDao;

??? private String??? name;

??? private Integer?? id;

??? /**

???? * @return the peopleDao

???? */

??? public PeopleDao getPeopleDao() {

??????? return peopleDao;

??? }

??? /**

???? * @param peopleDao the peopleDao to set

?? ??*/

??? public void setPeopleDao(PeopleDao peopleDao) {

??????? this.peopleDao = peopleDao;

??? }

??? /**

???? * @return the name

???? */

??? public String getName() {

??????? return name;

??? }

??? /**

???? * @param name the name to set

???? */

??? public void setName(String name) {

??????? this.name = name;

??? }

??? /**

???? * @return the id

???? */

??? public Integer getId() {

??????? return id;

??? }

??? /**

???? * @param id the id to set

???? */

??? public void setId(Integer id) {

??????? this.id = id;

??? }

??? public void save() {

??????? System.out.println("--> the method is called save()! name=" + name + ",id=" + id);

??????? peopleDao.add();

??? }

}

4、读取属性值，修改WxyClassPathXMLApplicationContext.java, 添加注入属性功能?：?

package com.wxy.content;

import java.beans.IntrospectionException;

import java.beans.Introspector;

import java.beans.PropertyDescriptor;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.net.URL;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import org.apache.commons.beanutils.ConvertUtils;

import org.dom4j.Document;

import org.dom4j.Element;

import org.dom4j.XPath;

import org.dom4j.io.SAXReader;

import com.wxy.bean.BeanDefinition;

import com.wxy.bean.PropertyDefinition;

/**

*? 自定义IoC容器

*? BeanDefinition的resource定位:readXML();

*? BeanDefinition的载入和解析 :readXML();

*? BeanDefinition在IoC容器中的注册 instanceBeans();

*?? @create-time???? 2011-8-10?? 上午09:19:17??

*? ?@revision????????? $Id

public class WxyClassPathXMLApplicationContext {

??? //存放BeanDefinition的列表，在beans.xml中定义的bean可能不止一个

??? private final List<BeanDefinition> beanDefines = new ArrayList<BeanDefinition>();

??? //将类名作为索引，将创建的Bean对象存入到Map中

??? private final Map<String, Object>? sigletons?? = new HashMap<String, Object>();

??? public WxyClassPathXMLApplicationContext(String fileName) {

??????? //读取xml配置文件

??????? this.readXML(fileName);

??????? //实例化bean

??????? this.instanceBeans();

??????? //注入对象

? ??????this.injectObject();

??? }

??? /**

???? *为bean对象的属性注入值

???? */

??? private void injectObject() {

??????? for (BeanDefinition beanDefinition : beanDefines) {

??????????? //获取beanDefines中的对象

??????????? Object bean = sigletons.get(beanDefinition.getId());

??????????? if (bean != null) {

??????????????? //如果存在，利用反射技术将值注入

??????????????? try {

??????????????????? //获取Bean的描述属性类

??????????????????? PropertyDescriptor[] ps = Introspector.getBeanInfo(bean.getClass())

??????????????????????? .getPropertyDescriptors();

??????????????????? for (PropertyDefinition propertyDefinition : beanDefinition.getProperties()) {

??????????????????????? for (PropertyDescriptor properdesc : ps) {

??????????????????????????? //取得属性名字与propertyDefinition中的属性做比较

??????????????????????????? if (propertyDefinition.getName().equals(properdesc.getName())) {

??????????????????????????????? //获得属性的setter方法

??????????????????????????????? Method setter = properdesc.getWriteMethod();

??????????????????????????????? if (setter != null) {

??????????????????????????????????? Object value = null;

??????????????????????????????????? if (propertyDefinition.getRef() != null

??????????????????????????????????????? && !propertyDefinition.getRef().isEmpty()) {//注入依赖对象

???????????? ???????????????????????????value = sigletons.get(propertyDefinition.getRef());

??????????????????????????????????? } else {//注入基本类型

??????????????????????????????????????? //将字符串类型装换成用户需要的类型，需要用到jar包中的commons-beanutils.jar

???????????????????????????????? ???????value = ConvertUtils.convert(propertyDefinition.getValue(),

??????????????????????????????????????????? properdesc.getPropertyType());

??????????????????????????????????? }

??????????????????????????????????? //允许访私有方法

????????????????????????????? ??????setter.setAccessible(true);

??????????????????????????????????? //把引用对象注入到属性

??????????????????????????????????? setter.invoke(bean, value);

??????????????????????????????? }

??????????????????????????? }

??????????????????????? }

?????????????????? ?}

??????????????? } catch (SecurityException e) {

??????????????????? // TODO Auto-generated catch block