手把手教你学spring之springIOC（一）

spring IOC （Inversion of Control，控制反转）

从这一小节开始，我们进入spring的学习

在学习之前我把之前所有的代码都共享出来，方便大家学习 探讨。

代码地址：

https://gitee.com/cgyspace/code-demos

选用的spring版本： 5.2.13.RELEASE

基于xml配置方式

• 先创建几个java类

  package com.cgy.spring5.ioc.entity;
  
  public class User {
      private String userName;
      private String password;
  
      public String getUserName() {
          return userName;
      }
  
      public void setUserName(String userName) {
          this.userName = userName;
      }
  
      public String getPassword() {
          return password;
      }
  
      public void setPassword(String password) {
          this.password = password;
      }
  }
  
  

  package com.cgy.demos.spring5.ioc.dao;
  
  import com.cgy.demos.spring5.ioc.entity.User;
  
  public class UserDao {
  
      public User getUserByName(String userName){
          User user = new User();
          user.setUserName(userName);
          user.setPassword("123456");
          return user;
      }
  }
  
  

  package com.cgy.spring5.ioc.service;
  
  import com.cgy.demos.spring5.ioc.dao.UserDao;
  import com.cgy.demos.spring5.ioc.entity.User;
  
  public class UserService {
  
      private UserDao userDao;
  
      public User getUserByName(String userName){
          return  userDao.getUserByName(userName);
      }
  
  
      public void setUserDao(UserDao userDao) {
          this.userDao = userDao;
      }
  }
  
  

  package com.cgy.spring5.ioc.service;
  
  import com.cgy.demos.spring5.ioc.entity.User;
  
  public class LoginService {
  
      public String login(User user){
          if (user!=null&& user.getUserName()!=null){
              return user.getUserName() + "登录成功";
          }
          return  "登录失败";
      }
  }
  
  

  这里准备了两个service 和一个dao 还有一个实体类 User

在resources目录下创建context.xml 内容如下

<?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.xsd">

 <bean id="loginService" class="com.cgy.spring5.ioc.service.LoginService">

 </bean>
 <bean name="userService" class="com.cgy.spring5.ioc.service.UserService">
  <property name="userDao" ref="userDao"></property>
 </bean>
<bean name="userDao" class="com.cgy.spring5.ioc.dao.UserDao">

</bean>
</beans>

创建测试类

package com.cgy.spring5.ioc;

import com.alibaba.fastjson.JSON;
import com.cgy.spring5.ioc.entity.User;
import com.cgy.spring5.ioc.service.LoginService;
import com.cgy.spring5.ioc.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {
    public static void main(String[] args) {
        ApplicationContext context = new ClassPathXmlApplicationContext("context.xml");
        UserService userService = context.getBean(UserService.class);
        LoginService loginService = (LoginService) context.getBean("loginService");
        User user = userService.getUserByName("张三");
        System.out.println(JSON.toJSONString(user));
        System.out.println(loginService);
    }
}

查看输出结果

几点说明： 用这种方式注入的 需要有setter方法，如果没有的话会报错。后面讲DI的时候也会说到

​ ApplicationContext context = new ClassPathXmlApplicationContext(“context.xml”); 这里的context.xml默认是classpath 目录下，如果改其他地方，请指定清楚，不然会找不到配置文件

静态工厂创建

 <bean name="clientService" class="com.cgy.spring5.ioc.service.ClientService"
 factory-method="getInstance" > <!-- 这里必须是静态工厂方法 -->

 </bean>

package com.cgy.spring5.ioc.service;

public class ClientService {


    private     String mark = "ClientService";
    private static ClientService clientService = new ClientService();

    private ClientService(){

    }
     public static ClientService getInstance(){
        return clientService;
    }

    public String getMark() {
        return mark;
    }

    public void setMark(String mark) {
        this.mark = mark;
    }

}

加入入参的静态工厂

<?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.xsd">

    <bean name="clientService" class="com.cgy.spring5.ioc.service.ClientService" factory-method="getInstance">
        <constructor-arg type="java.lang.String" value="测试输入参数"></constructor-arg>

    </bean>
 

package com.cgy.spring5.ioc.service;

public class ClientService {



    private static ClientService clientService = new ClientService();

    private ClientService(){

    }
     public static ClientService getInstance(String mark){
         System.out.println(mark);
        return clientService;
    }


}

工厂方法创建多个bean

<?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.xsd">
<bean name="serviceFactory" class="com.cgy.spring5.ioc.service.ServiceFactory">

</bean>
 <bean name="userService"   factory-bean="serviceFactory" factory-method= "getUserService"> <!--这里不能是静态方法-->

 </bean>
 <bean name="loginService"   factory-bean="serviceFactory" factory-method= "getLoginService">

 </bean>


</beans>

package com.cgy.spring5.ioc.service;

public class ServiceFactory {

    private static LoginService loginService = new LoginService();
    private static  UserService userService = new UserService();

    public   LoginService getLoginService(){
        return loginService;
    }
    public   UserService getUserService(){

        return userService;
    }

}

加入参数的工厂方法

<?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.xsd">
    <bean name="serviceFactory" class="com.cgy.spring5.ioc.service.ServiceFactory">

    </bean>
    <bean name="userService"   factory-bean="serviceFactory" factory-method= "getUserService"> <!--这里不能是静态方法-->
  <constructor-arg type="java.lang.String" value="这是一个标记"/>
    </bean>
    <bean name="loginService"   factory-bean="serviceFactory" factory-method= "getLoginService">
        <constructor-arg type="java.lang.String" value="这是另一个标记"/>
    </bean>


</beans>

package com.cgy.spring5.ioc.service;

public class ServiceFactory {

    private static LoginService loginService = new LoginService();
    private static  UserService userService = new UserService();

    public   LoginService getLoginService(String mark){
        System.out.println(mark);
        return loginService;
    }
    public   UserService getUserService(String mark){
        System.out.println(mark);
        return userService;
    }

}

说明：

这里的 factory-method 只会在context 初始化的时候调用一次，并把获取到的bean 放入容器中，如果你下次再获取这个bean 依然容器中创建好的同一个bean