1_Spring IOC-基于XML

1.配置pom文件

• 指定版本

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
    <mybatis.version>3.5.6</mybatis.version>
    <spring.version>5.2.9.RELEASE</spring.version>
  </properties>

• 导入依赖

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>${spring.version}</version>
    </dependency>
     <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context-support</artifactId>
      <version>${spring.version}</version>
    </dependency>
  

2.快速入门

1. dao的实现类其中一个UserDaoImpl ```java package com.jie.ssm.dao.impl;

import com.jie.ssm.dao.UserDao; import com.jie.ssm.entity.User;

import java.util.List;

public class UserDaoImpl implements UserDao { @Override public List selectUsers() { System.out.println(“UserDaoImpl”); return null; }

@Override
public User selectByUsername(String username) {
    return null;
}

@Override
public int insert(User user) {
    return 0;
}

@Override
public void update(User user) {

}

@Override
public int delete(int id) {
    return 0;
}

}

2. 
service的实现类
```java
package com.jie.ssm.service.impl;


import com.jie.ssm.dao.UserDao;
import com.jie.ssm.entity.User;
import com.jie.ssm.service.UserService;

import java.util.List;

public class UserServiceImpl implements UserService {
    private UserDao userDao;

    @Override
    public List<User> getAll() {
        return userDao.selectUsers();
    }

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }
}

• 不需要给userDao具体的实现类，通过下面的配置完成注入
  1. beans.xml配置注入 ```xml <?xml version=”1.0” encoding=”UTF-8”?>

<bean id="userDao" class="com.jie.ssm.dao.impl.UserDaoImpl"/>

<bean id="userService" class="com.jie.ssm.service.impl.UserServiceImpl">
    <property name="userDao" ref="userDao"/>
</bean>

   - 使userServiceImpl依赖于UserDaoImpl
4. 
测试类
```java
package com.jie.ssm.service;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class UserServiceTest {

    @Test
    public void test(){

        ApplicationContext context = new ClassPathXmlApplicationContext("beans.xml");

        UserService userService = context.getBean(UserService.class);

        userService.getAll();
    }
}

• 只需要改变beans.xml中配置可以将service实现类中的UserDao的实现改变

3.包扫描

1. beans.xml ```xml <?xml version=”1.0” encoding=”UTF-8”?>

<br />通过包路径进行扫描，如果扫描到有注解的，会将该类放到容器中

2. 
在dao层实现类上注解[@Repository ](/Repository ) 
```java
package com.jie.ssm.dao.impl;

import com.jie.ssm.dao.UserDao;
import com.jie.ssm.entity.User;
import org.springframework.stereotype.Repository;

import java.util.List;
@Repository
public class UserDaoImpl implements UserDao {
    @Override
    public List<User> selectUsers() {
        System.out.println("UserDaoImpl");
        return null;
    }

    @Override
    public User selectByUsername(String username) {
        return null;
    }

    @Override
    public int insert(User user) {
        return 0;
    }

    @Override
    public void update(User user) {

    }

    @Override
    public int delete(int id) {
        return 0;
    }
}

若有多个@Repository注解同一个接口的不同实现类会报异常，因为不唯一，可以在某一个实现类的@Repository上再添加一个@Primary注解

1. 在service实现类上添加注解@Service ```java package com.jie.ssm.service.impl;

import com.jie.ssm.dao.UserDao; import com.jie.ssm.entity.User; import com.jie.ssm.service.UserService; import org.springframework.stereotype.Service;

import java.util.List;

@Service public class UserServiceImpl implements UserService { @Autowired private UserDao userDao;

@Override
public List<User> getAll() {
    return userDao.selectUsers();
}

public void setUserDao(UserDao userDao) {
    this.userDao = userDao;
}

} ```

• 控制层@Controller，角色不明确用@Component
• @Autowired在属性上会从容器中赋值给这个属性