【JavaEE案例】spring中的Bean的管理

Dear 丶 2024-03-23 12:31 111阅读 0赞

【案例介绍】

（1）Bean的装配方式之基于注解的装配。

![db7ee618ec27439a98dcb56058cf737d.png][]

（2）Bean的生命周期。

![7266cb917add4ab493fe7c84fc9a357f.png][]

【案例实现】

![870b97b3f6794a98bb60b6d42d6cfabe.png][]

*  创建项目

![e4801ec459cf40ea9e643c752c464828.png][]

*  引入相关依赖：在**pom.xml**文件中加载Spring依赖包。

<?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">
        <modelVersion>4.0.0</modelVersion>
    
        <groupId>com.itheima</groupId>
        <artifactId>userManager</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <properties>
            <maven.compiler.source>17</maven.compiler.source>
            <maven.compiler.target>17</maven.compiler.target>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-context</artifactId>
                <version>5.3.16</version>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.12</version>
            </dependency>
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-aop</artifactId>
                <version>5.2.8.RELEASE</version>
            </dependency>
            <dependency>
                <groupId>javax.annotation</groupId>
                <artifactId>javax.annotation-api</artifactId>
                <version>1.3.2</version>
            </dependency>
        </dependencies>
    
    </project>

1.1 在src/main/resources目录下创建**applicationContext.xml**，在该文件中引入Context约束并启动Bean的自动扫描功能。

<?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:context="http://www.springframework.org/schema/context"
           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">
        
        <context:component-scan base-package="com.itheima" />
    </beans>

1.2 定义实体类

在com.itheima包下新建entity包，在entity包下新建**User**实体类。

package com.itheima.entity;
    
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.context.annotation.Scope;
    import org.springframework.stereotype.Component;
    
    @Component("user")
    @Scope("singleton")
    
    public class User {
        @Value("1")
        private int id;
        @Value("张三")
        private String name;
        @Value("123")
        private String password;
        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getPassword() {
            return password;
        }
        public void setPassword(String password) {
            this.password = password;
        }
        public String toString(){
            return "id="+id+",name="+name+",password="+password;
        }
    }

1.3 编写DAO层

在com.itheima包下创建dao包，在dao包下创建**接口UserDao**作为数据访问层接口，并在**UserDao接口**中声明save()方法，用于查询User实体的对象信息。

package com.itheima.dao;
    
    public interface UserDao {
        public void save(); //用于查询user实体的对象信息
    }

在com.itheima.dao包下创建**UerDaoImpl作为**UserDao接口的实现类，并在**UerDaoImpl类**中实现UserDao接口中的save()方法。

package com.itheima.dao;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    import org.springframework.stereotype.Repository;
    import com.itheima.entity.User;
    
    //使用@Repository注解将UserDaoImpl类标识为Spring中的Bean
    @Repository("userDao")
    
    public class UserDaoImpl implements UserDao {
        public void save(){
            //代码加载applicationContext.xml配置文件
            ApplicationContext applicationContext=new ClassPathXmlApplicationContext("applicationContext.xml");
            //User实例化
            User user=(User) applicationContext.getBean("user");
            //打印实例化后的user和提示信息
            System.out.println(user);
            System.out.println("执行UserDaoImpl.save()");
        }
    }

1.4 编写Service层

在com.itheima包下新建service包，在service包下创建**UserService接口**作为业务逻辑层接口，并在**UserService****接口**中定义save()方法。

package com.itheima.service;
    
    public interface UserService {
        public void save();
    }

在com.itheima.dao包下创建**UserServiceImpl作为**UserService接口的实现类，并在**UserServiceImpl类**中实现UserService接口中的save()方法。

package com.itheima.service;
    
    import com.itheima.dao.UserDao;
    import org.springframework.stereotype.Service;
    import javax.annotation.Resource;
    
    //使用@Service注解将UserServiceImpl类标识为Spring中的Bean
    @Service("userService")
    
    public class UserServiceImpl implements UserService {
        //使用@Resource注解注入UserDao
        @Resource(name="userDao")
        private UserDao userDao;
        public void save(){
            this.userDao.save();
            System.out.println("执行UserServiceImpl.save()");
        }
    }

1.5 编写Controller层

在com.itheima包下新建controller包，在service包下创建**UserController类**作为控制层。

package com.itheima.controller;
    
    import org.springframework.stereotype.Controller;
    import com.itheima.service.UserService;
    import javax.annotation.Resource;
    
    //使用Controller注解将UserController类标识为Spring中的Bean
    @Controller
    
    public class UserController {
        //使用@Resource注解注入UserService
        @Resource(name="userService")
        private UserService userService;
        public void save(){
            this.userService.save();
            System.out.println("执行UserController.save()");
        }
    }

1.6 编写测试类**AnnotationTest.java**

package com.itheima;
    
    import com.itheima.controller.UserController;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    public class AnnotationTest {
        public  static  void main (String[] args){
            ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
            UserController userController = (UserController)  applicationContext.getBean("userController");
            userController.save();
    
        }
    }

2.1 在com.itheima包下创建**Student类**，在类中定义id和name字段，并使用@PostConstruct指定初始化方法，使用@PreDestroy指定Bean销毁前的方法。

package com.itheima;
    
    import org.springframework.beans.factory.annotation.Value;
    import org.springframework.stereotype.Component;
    import javax.annotation.PostConstruct;
    import javax.annotation.PreDestroy;
    
    @Component("student")
    
    public class Student {
        @Value("1")
        private String id;
        @Value("张三")
        private String name;
        public String getId() {
            return id;
        }
        public void setId(String id) {
            this.id = id;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        @PostConstruct
        public  void init(){
            System.out.println("Bean对象的初始化完成，调用init（）的方法");
        }
        @PreDestroy
        public void destroy(){
            System.out.println("Bean销毁调用destroy（）方法");
        }
        public String toString(){
            return "id="+id+",name="+name;
        }
    }

2.2 在src/main/resources目录下创建**applicationStudent.xml**，在该文件中引入Context约束并启动Bean的自动扫描功能。

2.3 编写测试类**StudentTest.java**

package com.itheima;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.AbstractApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    public class StudentTest {
        public static  void main (String[] args){
            ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationStudent.xml");
            Student student = (Student) applicationContext.getBean("student");
            System.out.println(student);
            AbstractApplicationContext ac=(AbstractApplicationContext)  applicationContext;
            ac.registerShutdownHook();
        }
    }

[db7ee618ec27439a98dcb56058cf737d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/23/20133307a0aa490885235c225d687dbd.png
[7266cb917add4ab493fe7c84fc9a357f.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/23/e26947b8c0b440be836ef18b4d236f6c.png
[870b97b3f6794a98bb60b6d42d6cfabe.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/23/d8d1211de46347e7abaefee56ac58ede.png
[e4801ec459cf40ea9e643c752c464828.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/23/e0b3d5fb4a3643fe98f8bed00448f1db.png