尚学堂Spring视频教程（三）：Spring Core中的其他特性

集合装配

  如果bean中有一些集合属性，配置文件的配置如下

package com.bjsxt.dao.impl;

import java.util.List;
import java.util.Map;
import java.util.Set;

import com.bjsxt.dao.UserDAO;
import com.bjsxt.model.User;

public class UserDAOImpl implements UserDAO {
    /* (non-Javadoc)
     * @see com.bjsxt.dao.UserDAO#save(com.bjsxt.model.User)
     */
    private Set<String> sets;
    private List<String> lists;
    private Map<String , String> maps;
    
    
    public Set<String> getSets() {
        return sets;
    }



    public void setSets(Set<String> sets) {
        this.sets = sets;
    }



    public List<String> getLists() {
        return lists;
    }



    public void setLists(List<String> lists) {
        this.lists = lists;
    }



    public Map<String, String> getMaps() {
        return maps;
    }



    public void setMaps(Map<String, String> maps) {
        this.maps = maps;
    }



    public UserDAOImpl() {
    }
    
    

    public void save(User user) {
        System.out.println("user saved!");
    }
    
    @Override
    public String toString() {
        return "sets size:" + sets.size() + "| lists size:" + lists.size() + "| maps size:" + maps.size() ; 
    }

}

<?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 name="userDAO" class="com.bjsxt.dao.impl.UserDAOImpl">
      <property name="sets">
          <set>
              <value>1</value>
              <value>2</value>
          </set>
      </property>
      <property name="lists">
          <list>
              <value>1</value>
              <value>2</value>
              <value>3</value>
          </list>
      </property>
      <property name="maps">
          <map>
              <entry key="1" value="1"></entry>
              <entry key="2" value="2"></entry>
              <entry key="3" value="3"></entry>
              <entry key="4" value="4"></entry>
          </map>
      </property>
  </bean>

  <bean id="userService" class="com.bjsxt.service.UserService">
  <!-- 
      <property name="userDAO">
          <ref bean="userDAO"/>
      </property>
       -->
       <constructor-arg>
           <ref bean="userDAO"/>
       </constructor-arg>
  </bean>


</beans>

自动装配

  如果每个属性都使用ref配置，一个大项目的Spring配置会十分庞大，可以通过<bean>的autowire属性设置自动装配规则。使用后不需要再用<property>子标签设置该bean的属性、依赖关系。Spring会根据反射，自动寻找符合该条件的属性，设置到该bean属性上。如果autowire设置为byType，将会按照属性的类型自动装配，注意如果找到多个该属性类型的bean，会抛出异常。如果是byName，根据名称自动装配，例如如果bean中有个名为datasource的属性，Spring会把id为datasource的bean设置到该bean中

Bean的生命周期

  lazy-init：spring默认的是在启动时创建所有的bean的对象，如果一个项目很大，有500个bean，这些bean会一次性全部加载到内存中，会造成启动速度特别慢，将这个属性设置为true，那么beanfactory在调用getbean方法的时候该bean才会被创建

  init-method:bean在实例化之后执行的方法

  destroy-method:bean使用完毕后执行的方法

<?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 lazy-init="true" id="u" class="com.bjsxt.dao.impl.UserDAOImpl">
  </bean>
    
  <bean id="userService" class="com.bjsxt.service.UserService" init-method="init" destroy-method="destroy" scope="singleton">
      <!-- 
      <property name="userDAO" ref="u" />
       -->
       <constructor-arg>
           <ref bean="u"/>
       </constructor-arg>
  </bean>
  

</beans>

package com.bjsxt.service;
import com.bjsxt.dao.UserDAO;
import com.bjsxt.model.User;



public class UserService {
    
    private UserDAO userDAO;  
    
    public void init() {
        System.out.println("init");
    }
    
    public void add(User user) {
        userDAO.save(user);
    }
    public UserDAO getUserDAO() {
        return userDAO;
    }
    public void setUserDAO(UserDAO userDAO) {
        this.userDAO = userDAO;
    }
    
    public UserService(UserDAO userDAO) {
        super();
        this.userDAO = userDAO;
    }
    
    public void destroy() {
        System.out.println("destroy");
    }
}

package com.bjsxt.service;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.bjsxt.model.User;

//Dependency Injection
//Inverse of Control
public class UserServiceTest {

    @Test
    public void testAdd() throws Exception {
        ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml");
        
        
        UserService service = (UserService)ctx.getBean("userService");
        UserService service2 = (UserService)ctx.getBean("userService");
        
        ctx.destroy();
        
    }

}

执行结果

  注：因为我们配置文件中bean的scope属性设置为了singleton，表示该对象单例，所以实例化两次其实还是同一个对象，如果改为prototype，会输出两个init，不会执行detroy-method指定的方法，具体原因不明，可以查阅相关资料