Spring见解2

3.基于注解的IOC配置

学习基于注解的IOC配置,大家脑海里首先得有一个认知,即注解配置和xml配置要实现的功能都是一样的,都是要降低程序间的耦合。只是配置的形式不一样。4

3.1.创建工程

Spring见解2_第1张图片

3.1.1.pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>spring</artifactId>
        <groupId>com.by</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.by</groupId>
    <artifactId>Spring_IOC_Annotation</artifactId>

    <properties>
        <!-- 项目源码及编译输出的编码 -->
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <!-- 项目编译JDK版本 -->
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

    <dependencies>
        <!-- Spring常用依赖 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.1.8.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.7.30</version>
        </dependency>
    </dependencies>
</project>

3.1.2.dao

package com.by.dao;

import org.springframework.stereotype.Repository;

@Repository
public class UserDaoImpl implements UserDao{

    @Override
    public void addUser(){
        System.out.println("insert into tb_user......");
    }
}

3.1.3.service

package com.by.service;

import com.by.dao.UserDao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;

@Service
@Scope("prototype")
public class UserServiceImpl implements UserService{
    //@Resource(name="userDaoImpl") //按名称从容器中获得bean,并注入给userDao
    @Autowired
    private UserDao userDao;
    @Value("${name}")//${name}:从ioc容器中获得“name”的值,@Value():并注入给name
    private String name;
    @Value("${age}")
    private Integer age;
    @Override
    public void addUser() {
        System.out.println(userDao+"     "+name+"      "+age);
        userDao.addUser();
    }
}

3.2.IOC

3.2.1.applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       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
				http://www.springframework.org/schema/context
      			http://www.springframework.org/schema/context/spring-context.xsd ">
    <!--加载config.properties配置文件,并把配置文件中的数据存到IOC容器中-->
    <context:property-placeholder location="config.properties"></context:property-placeholder>
    <!--
        告诉spring,容器启动时要扫描的包,且spring会依据注解创建对象并存到IOC容器中
    -->
    <context:component-scan base-package="com.by"></context:component-scan>
</beans>

3.2.2.dao

package com.by.dao;

import org.springframework.stereotype.Repository;

@Repository
public class UserDaoImpl implements UserDao{

    @Override
    public void addUser(){
        System.out.println("insert into tb_user......");
    }
}

3.2.3.service

package com.by.service;

import com.by.dao.UserDao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;

@Service
@Scope("prototype")
public class UserServiceImpl implements UserService{
    //@Resource(name="userDaoImpl") //按名称从容器中获得bean,并注入给userDao
    @Autowired
    private UserDao userDao;
    @Value("${name}")//${name}:从ioc容器中获得“name”的值,@Value():并注入给name
    private String name;
    @Value("${age}")
    private Integer age;
    @Override
    public void addUser() {
        System.out.println(userDao+"     "+name+"      "+age);
        userDao.addUser();
    }
}

3.3.DI

3.3.1.service

package com.by.service;

import com.by.dao.UserDao;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;

@Service
@Scope("prototype")
public class UserServiceImpl implements UserService{
    //@Resource(name="userDaoImpl") //按名称从容器中获得bean,并注入给userDao
    @Autowired
    private UserDao userDao;
    @Value("${name}")//${name}:从ioc容器中获得“name”的值,@Value():并注入给name
    private String name;
    @Value("${age}")
    private Integer age;
    @Override
    public void addUser() {
        System.out.println(userDao+"     "+name+"      "+age);
        userDao.addUser();
    }
}

3.3.2.测试

package com.by.web;

import com.by.service.UserService;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class client {
    public static void main(String[] args) {
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService userService = ac.getBean("userServiceImpl", UserService.class);
        userService.addUser();

        for (int i = 0; i < 5; i++) {
            UserService userServicei = ac.getBean("userServiceImpl", UserService.class);
            System.out.println(userServicei);
        }
    }
}

3.3.常用注解

3.3.1.用于创建对象的

以下四个注解的作用及属性都是一模一样的,都是针对一个的衍生注解只不过是提供了更加明确的语义化。

3.3.1.1.@Controller
  • 作用:

    把资源交给spring来管理,相当于:;一般用于表现层。

  • 属性:

    value:指定bean的id;如果不指定value属性,默认bean的id是当前类的类名,首字母小写;

3.3.1.2.@Service
  • 作用:

    把资源交给spring来管理,相当于:;一般用于业务层。

  • 属性:

    value:指定bean的id;如果不指定value属性,默认bean的id是当前类的类名,首字母小写;

  • 案例

//@Service("userService")声明bean,且id="userServiceImpl"
@Service//声明bean,且id="userServiceImpl"
public class UserServiceImpl implements UserService {
 	...   
}
3.3.1.3.@Repository
  • 作用:

    把资源交给spring来管理,相当于:;一般用于持久层。

  • 属性:

    value:指定bean的id;如果不指定value属性,默认bean的id是当前类的类名,首字母小写;

  • 案例

//@Repository("userDaoImpl")声明bean,且id="userDaoImpl"
@Repository//声明bean,且id="userDaoImpl"
public class UserDaoImpl implements UserDao {

    @Override
    public void addUser(){
        System.out.println("insert into tb_user......");
    }
}
3.3.1.4.@Component
  • 作用:

    把资源交给spring来管理,相当于:;通用。

  • 属性:

    value:指定bean的id;如果不指定value属性,默认bean的id是当前类的类名,首字母小写;

3.3.1.5.@Scope
  • 作用:

    指定bean的作用域范围。

  • 属性:

    value:指定范围的值,singleton prototype request session。

3.3.2.用于属性注入的

以下四个注解的作用相当于:

3.3.2.1.@Autowired
  • 作用:

    自动按照类型注入。set方法可以省略。

  • 案例:

@Service
public class UserServiceImpl implements UserService {

    @Autowired //注入类型为UserDAO的bean
    private UserDao userDao;

    public void addUser(){
        userDao.addUser();
    }
}
3.3.2.1.@Resource
  • 作用:

    自动按照名字注入。set方法可以省略。

  • 属性:

​ name:指定bean的id。

  • 案例:
@Service
public class UserServiceImpl implements UserService {

    @Resource(name="userDaoImpl")//注入id=“userDaoImpl”的bean
    private UserDao userDao;

    public void addUser(){
        userDao.addUser();
    }
}
3.3.2.1.@Value
  • 作用:

    注入基本数据类型和String类型数据的

  • 属性:

​ value:用于指定值

  • 案例一
@Service
public class UserServiceImpl implements UserService {

    @Resource(name="userDaoImpl") //注入id=“userDaoImpl”的bean
    private UserDao userDao;
    @Value("张三")//注入String
    private String name;
    @Value("18")//注入Integer
    private Integer age;

    public void addUser(){
        System.out.println(name+","+age);
        userDao.addUser();
    }
}
  • 案例二
  1. 创建config.properties
name=张三
age=18
  1. 加载配置文件
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       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
			http://www.springframework.org/schema/context
      		http://www.springframework.org/schema/context/spring-context.xsd ">
    <!--加载config.properties-->
    <context:property-placeholder location="config.properties"/>
    <context:component-scan base-package="com.by"></context:component-scan>
</beans>
  1. 注入属性值
@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserDao userDao;
    @Value("${name}")//注入String
    private String name;
    @Value("${age}")//注入Integer
    private Integer age;

    public void addUser() {
        System.out.println(name+","+age);
        userDao.addUser();
    }
}

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