三种实例化bean的步骤

三种实例化bean的方法

情形如下：我们有一个PersonDaoImpl类，需要交给spring容器进行管理

PersonDao.java

package com.chris.dao;public interface PersonDao {public abstract void save();}

PersonDaoImpl.java

package com.chris.dao.impl;import com.chris.dao.PersonDao;public class PersonDaoImpl implements PersonDao {/* (non-Javadoc) * @see com.chris.dao.PersonDao#save() */@Overridepublic void save(){System.out.println("save....");}}

?

方法一：通过类默认构造器进行实例化

?????在spring配置文件beans.xml中配置如下代码

<?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/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd">....<bean name="personDaoBean" name="code">package com.chris.factory;import com.chris.dao.PersonDao;import com.chris.dao.impl.PersonDaoImpl;public class PersonDaoFactory {//静态工厂方法public static PersonDao getInstence(){return new PersonDaoImpl();}}

?在spring配置文件beans.xml中配置如下代码

<?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/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd">....<bean name="personDaoBean" factory-method="getInstence"/> <!--class属性为静态工厂类 factory-method为静态工厂方法-->                      ....</beans>

?方法三：通过实例工厂进行实例化

实例工厂类PersonDaoFactory.java

package com.chris.factory;import com.chris.dao.PersonDao;import com.chris.dao.impl.PersonDaoImpl;public class PersonDaoFactory {public PersonDao getInstence(){return new PersonDaoImpl();}}

?

?在spring配置文件beans.xml中配置如下代码

<?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/beanshttp://www.springframework.org/schema/beans/spring-beans-3.0.xsd"><!--首先配置实例工厂，将实例工厂交给容器管理 --><bean name = "personDaoFacotry" class = "com.chris.factory.PersonDaoFactory"/><!--factory-bean中填写实例工厂在容器中的名称   factory-method为工厂中获取对象实例方法--><bean name = "personDaoBean" factory-bean="personDaoFacotry" factory-method="getInstence"/></beans>

??

经过上述三种方法任选一种进行配置后，我们就可以从spring容器中获取我们需要的PersonDaoImpl对象了

ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");PersonDao personDao = (PersonDao) applicationContext.getBean("personDaoBean");personDao.save();

?