Spring IOC & DI

 

新建Maven项目，设置Maven版本，配置文件与Maven仓库，在代码引入之前，需要用代码实现以下

• User模块实体类：User.java

package entity;

public class User {
private Integer id;
private String name;
private Integer gender;
}

• User模块视图类：UserVo.java

package vo;

public class UserVo {
private Integer id;
private String name;
private Integer gender;
private String genderName;
public UserVo() {
}
public UserVo(User user) {
this.id = user.getId();
this.name = user.getName();
this.gender = user.getGender();
}
}

• User模块Dao层：UserDao.java

package dao;

public interface UserDao {
User getEntity(Integer id);
}

• User模块Dao层实现类：UserDaoImpl.java

package dao.impl;

public class UserDaoImpl implements UserDao {
public User getEntity(Integer id) {
User user = new User();
user.setId(1);
user.setName("Anne");
user.setGender(0);
return user;
}
}

• User模块Service层：UserService.java

package services;

public interface UserService {
UserVo getVo(Integer id);
}

• User模块Service层实现类：UserServiceImpl.java

package services.impl;

public class UserServiceImpl implements UserService {
private UserDao userDao;

public UserVo getVo(Integer id) {
userDao = new UserDaoImpl();
User user = userDao.getEntity(id);
UserVo userVo = new UserVo(user);
userVo.setGenderName(userVo.getGender() == 0 ? "female" : "male");
return userVo;
}
}

• User模块Controller层：UserController.java

package controller;

public class UserController {
private UserService userService;

public UserVo getVo(Integer id) {
userService = new UserServiceImpl();
return userService.getVo(id);
}
}

• User模块测试类：UserTest.java

public class UserTest {
public static void main(String[] args) {
UserController userController = new UserController();
UserVo userVo = userController.getVo(1);
System.out.println(userVo);
}
}

引入IOC

<bean id="userDao" class="dao.impl.UserDaoImpl"/>
<bean id="userService" class="services.impl.UserServiceImpl"/>
<bean id="userController" class="controller.UserController"/>

• User模块测试类：UserTest.java

public class UserTest {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
UserController userController = (UserController) context.getBean("userController");
UserVo userVo = userController.getVo(1, context);
System.out.println(userVo);
}
}

• User模块Controller层：UserController.java

package controller;

public class UserController {
private UserService userService;

public UserVo getVo(Integer id, ApplicationContext context) {
userService = (UserService) context.getBean("userService");
return userService.getVo(id, context);
}
}

• User模块Service层实现类：UserServiceImpl.java

package services.impl;

public class UserServiceImpl implements UserService {
private UserDao userDao;

public UserVo getVo(Integer id, ApplicationContext context) {
userDao = (UserDao) context.getBean("userDao");
User user = userDao.getEntity(id);
UserVo userVo = new UserVo(user);
userVo.setGenderName(userVo.getGender() == 0 ? "female" : "male");
return userVo;
}
}

 

引入IOC(XML)

代码实现

要想使用SpringIOC首先需要导入Spring框架基础包并且添加Spring核心配置文件

将依赖交给Spring的beanFactory管理

 <bean id="userDao" class="dao.impl.UserDaoImpl"/>
<bean id="userService" class="services.impl.UserServiceImpl"/>
<bean id="userController" class="controller.UserController"/>

User模块测试类：UserTest.java

1. 读取配置文件刷新Spring容器
2. Controller由手动实例化改为从Spring容器拿取
3. 把ApplicationContext传到Controller层继续使用

public class UserTest {
    public static void main(String[] args) {
        // 读取配置文件刷新Spring容器
        ApplicationContext context = new ClassPathXmlApplicationContext("classpath:applicationContext.xml");
        // 从Spring容器拿Controller
        UserController userController = (UserController) context.getBean("userController");
        // 执行Controller层方法，因为之后还需要用到context对象，故下传
        UserVo userVo = userController.getVo(1, context);
        System.out.println(userVo);
    }
}

User模块Controller层：UserController.java

1. Service由手动实例化改为从Spring容器拿取
2. 把ApplicationContext传到Service层继续使用

 

package controller;

public class UserController {
    private UserService userService;

    public UserVo getVo(Integer id, ApplicationContext context) {
        // 从Spring容器拿Service
        userService = (UserService) context.getBean("userService");
        // 执行Service层方法，因为之后还需要用到context对象，故下传
        return userService.getVo(id, context);
    }
}

User模块Service层实现类：UserServiceImpl.java

Dao由手动实例化改为从Spring容器拿取

package services.impl;

public class UserServiceImpl implements UserService {
    private UserDao userDao;

    public UserVo getVo(Integer id, ApplicationContext context) {
        // 从Spring容器拿Dao
        userDao = (UserDao) context.getBean("userDao");
        // 执行Dao层方法
        User user = userDao.getEntity(id);
        // 省略业务逻辑处理。。。
        UserVo userVo = new UserVo(user);
        userVo.setGenderName(userVo.getGender() == 0 ? "female" : "male");
        return userVo;
    }
}

XML改注解(IOC)

核心配置文件修改

context-component-scan标签Spring框架自定义的xml标签，通过base-package属性指明需要被自动扫描实例化的类所在位置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:util="http://www.springframework.org/schema/util"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/util
        https://www.springframework.org/schema/util/spring-util.xsd
        http://www.springframework.org/schema/context
        https://www.springframework.org/schema/context/spring-context.xsd
       ">

    <!-- bean definitions here -->
    <context:component-scan base-package="dao"/>
    <context:component-scan base-package="services"/>
    <context:component-scan base-package="controller"/>

</beans>

引入DI

User模块Controller层：UserController.java

package controller;

@Controller
public class UserController {
    // 改为自动注入
    @Autowired
    private UserService userService;

    public UserVo getVo(Integer id, ApplicationContext context) {
        // 执行Service层方法，因为之后还需要用到context对象，故下传
        return userService.getVo(id, context);
    }
}

User模块Dao层实现类：UserDaoImpl.java

去除指定bean id，改为默认bean id（userDaoImpl）

package dao.impl;

// 改为默认bean id“userDaoImpl”
@Repository
public class UserDaoImpl implements UserDao {
    public User getEntity(Integer id) {
        // 此处应该从数据库查询值 方便起见直接返回一个固定对象
        User user = new User();
        user.setId(1);
        user.setName("Anne");
        user.setGender(0);
        return user;
    }
}

User模块Service层实现类：UserServiceImpl.java

改为自动注入并指定需要注入的实例id

package services.impl;

@Service("userService")
public class UserServiceImpl implements UserService {
    // 改为自动注入并指定需要注入的实例id
    @Autowired
    @Qualifier("userDaoImpl")
    private UserDao userDao;

    public UserVo getVo(Integer id) {
        // 执行Dao层方法
        User user = userDao.getEntity(id);
        // 省略业务逻辑处理。。。
        UserVo userVo = new UserVo(user);
        userVo.setGenderName(userVo.getGender() == 0 ? "female" : "male");
        return userVo;
    }
}