Spring 基于注解装配Bean

傷城~ 2022-02-09 12:21 392阅读 0赞

### 文章目录 ###

*   *  Spring 基于注解的配置
     *   *  创建Bean
         *  依赖注入
         *   *  普通值注入
             *  引用值注入
             *  生命周期
             *  作用域

## Spring 基于注解的配置 ##

从 Spring 2.5 开始就可以使用注解来配置依赖注入。而不是采用 XML 来描述一个 bean 连线，你可以使用相关类，方法或字段声明的注解，将 bean 配置移动到组件类本身。

*  注解：就是一个类，使用@注解名称
 *  开发中：使用注解 取代 xml配置文件。

### 创建Bean ###

@Component取代`<bean class="">`  
@Component(“id”) 取代 `<bean id="" class="">`

web开发，提供3个@Component注解衍生注解（功能一样）取代`<bean class="">`

*  @Repository ：dao层
 *  @Service：service层
 *  @Controller：web层

注解使用前提，添加命名空间，让spring扫描含有注解类

*  配置

*  schema命名空间  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Nja2V2aW5jeWg_size_16_color_FFFFFF_t_70]
 *  User

@Component("userId")
    public class User {
        private String username;
        private Address address;
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public Address getAddress() {
            return address;
        }
    
        public void setAddress(Address address) {
            this.address = address;
        }
    }

*  测试

@Test
        public void demo01(){
            String xmlPath = "annotation.xml";
            ApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
            User user = (User) applicationContext.getBean("userId");
            System.out.println(user);
        }

结果发现报错了，报错如下：

java.lang.IllegalArgumentException
    	at org.springframework.asm.ClassReader.<init>(Unknown Source)
    	at org.springframework.asm.ClassReader.<init>(Unknown Source)
    	at org.springframework.asm.ClassReader.<init>(Unknown Source)
    	at org.springframework.core.type.classreading.SimpleMetadataReader.<init>(SimpleMetadataReader.java:52)
    	at org.springframework.core.type.classreading.SimpleMetadataReaderFactory.getMetadataReader(SimpleMetadataReaderFactory.java:80)
    	at org.springframework.core.type.classreading.CachingMetadataReaderFactory.getMetadataReader(CachingMetadataReaderFactory.java:101)
    	at org.springframework.core.type.classreading.SimpleMetadataReaderFactory.getMetadataReader(SimpleMetadataReaderFactory.java:76)
    	at org.springframework.context.annotation.ConfigurationClassParser.getImports(ConfigurationClassParser.java:298)
    	at org.springframework.context.annotation.ConfigurationClassParser.getImports(ConfigurationClassParser.java:300)
    	at org.springframework.context.annotation.ConfigurationClassParser.getImports(ConfigurationClassParser.java:300)
    	at org.springframework.context.annotation.ConfigurationClassParser.doProcessConfigurationClass(ConfigurationClassParser.java:230)
    	at org.springframework.context.annotation.ConfigurationClassParser.processConfigurationClass(ConfigurationClassParser.java:153)
    	at org.springframework.context.annotation.ConfigurationClassParser.parse(ConfigurationClassParser.java:130)
    	at org.springframework.context.annotation.ConfigurationClassPostProcessor.processConfigBeanDefinitions(ConfigurationClassPostProcessor.java:285)
    	at org.springframework.context.annotation.ConfigurationClassPostProcessor.postProcessBeanDefinitionRegistry(ConfigurationClassPostProcessor.java:223)
    	at org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(AbstractApplicationContext.java:630)
    	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:461)
    	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
    	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
    	at com.cc.study.annotation.TestAnnotation.demo01(TestAnnotation.java:16)
    	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    	at java.lang.reflect.Method.invoke(Method.java:498)
    	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
    	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
    	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
    	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
    	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
    	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
    	at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    	at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
    	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:117)
    	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
    	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:262)
    	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:84)
    	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    	at java.lang.reflect.Method.invoke(Method.java:498)
    	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

然后我试了一下把Spring的版本改成4.0，把JDK改为1.8即可

<dependencies>
            
            
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-context</artifactId>
                <version>4.2.0.RELEASE</version>
            </dependency>
            
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-beans</artifactId>
                <version>4.2.0.RELEASE</version>
            </dependency>
            
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-core</artifactId>
                <version>4.2.0.RELEASE</version>
            </dependency>
            
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-expression</artifactId>
                <version>4.2.0.RELEASE</version>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.7</version>
            </dependency>
        </dependencies>
        <build>
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <configuration>
                        <source>1.8</source>
                        <target>1.8</target>
                    </configuration>
                </plugin>
            </plugins>
        </build>

测试结果：  
![在这里插入图片描述][20190502235030374.png]

### 依赖注入 ###

依赖注入，**给私有字段设置，也可以给setter方法设置**

#### 普通值注入 ####

**使用@Value**

*  User

@Component("userId")
    public class User {
        @Value("Kevin")
        private String username;
        private Address address;
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public Address getAddress() {
            return address;
        }
    
        public void setAddress(Address address) {
            this.address = address;
        }
    }

*  测试

@Test
        public void demo02(){
            String xmlPath = "annotation.xml";
            ApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
            User user = (User) applicationContext.getBean("userId");
            System.out.println(user.getUsername());
        }

![在这里插入图片描述][20190502235311474.png]

#### 引用值注入 ####

方式1：按照【类型】注入  
@Autowired

*  Address

@Component
    public class Address {
        @Value("北京")
        private String addr;
        @Value("112")
        private String tel;
    
        public String getAddr() {
            return addr;
        }
    
        public void setAddr(String addr) {
            this.addr = addr;
        }
    
        public String getTel() {
            return tel;
        }
    
        public void setTel(String tel) {
            this.tel = tel;
        }
    }

*  User

@Component("userId")
    public class User {
        @Value("Kevin")
        private String username;
        @Autowired
        private Address address;
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public Address getAddress() {
            return address;
        }
    
        public void setAddress(Address address) {
            this.address = address;
        }
    }

*  测试

@Test
        public void demo03(){
            String xmlPath = "annotation.xml";
            ApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
            User user = (User) applicationContext.getBean("userId");
            System.out.println(user.getUsername());
            System.out.println(user.getAddress().getAddr());
            System.out.println(user.getAddress().getTel());
        }

![在这里插入图片描述][20190502235617998.png]

方式2：按照【名称】注入1  
@Autowired  
@Qualifier(“名称”)

*  Address

@Component("addressId")
    public class Address {
        @Value("北京")
        private String addr;
        @Value("112")
        private String tel;
    
        public String getAddr() {
            return addr;
        }
    
        public void setAddr(String addr) {
            this.addr = addr;
        }
    
        public String getTel() {
            return tel;
        }
    
        public void setTel(String tel) {
            this.tel = tel;
        }
    }

*  User

@Component("userId")
    public class User {
        @Value("Kevin")
        private String username;
        @Autowired
        @Qualifier("addressId")
        private Address address;
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public Address getAddress() {
            return address;
        }
    
        public void setAddress(Address address) {
            this.address = address;
        }
    }

*  测试

![在这里插入图片描述][2019050223592567.png]

方式3：按照【名称】注入2  
@Resource(name=“名称”)

*  User

@Component("userId")
    public class User {
        @Value("Kevin")
        private String username;
    
        @Resource(name = "addressId")
        private Address address;
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public Address getAddress() {
            return address;
        }
    
        public void setAddress(Address address) {
            this.address = address;
        }
    }

*  测试

![在这里插入图片描述][20190503000457534.png]

#### 生命周期 ####

初始化：@PostConstruct  
销毁：@PreDestroy

*  User

*  测试

@Test
        public void demo04(){
            String xmlPath = "annotation.xml";
            AbstractApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
            User user = (User) applicationContext.getBean("userId");
            System.out.println(user.getUsername());
            System.out.println(user.getAddress().getAddr());
            System.out.println(user.getAddress().getTel());
            applicationContext.close();
        }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Nja2V2aW5jeWg_size_16_color_FFFFFF_t_70 1]

#### 作用域 ####

@Scope(“prototype”) 多例

*  User

@Component("userId")
    @Scope("prototype")
    public class User {
        @Value("Kevin")
        private String username;
    
        @Resource(name = "addressId")
        private Address address;
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public Address getAddress() {
            return address;
        }
    
        public void setAddress(Address address) {
            this.address = address;
        }
    
        @PostConstruct
        public void init(){
            System.out.println("初始化");
        }
        @PreDestroy
        public void destroy(){
            System.out.println("销毁");
        }
    }

*  测试

@Test
        public void demo05(){
            String xmlPath = "annotation.xml";
            AbstractApplicationContext applicationContext = new ClassPathXmlApplicationContext(xmlPath);
            User user1 = (User) applicationContext.getBean("userId");
            User user2 = (User) applicationContext.getBean("userId");
            System.out.println(user1);
            System.out.println(user2);
        }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Nja2V2aW5jeWg_size_16_color_FFFFFF_t_70 2]

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[20190502235030374.png]: /images/20220206/aaa9f99bcae242e4bcb07db2eeb10483.png
[20190502235311474.png]: /images/20220206/07e76571957a42bf8a03233025175e94.png
[20190502235617998.png]: /images/20220206/347c2f25b416401e8e84668eb51612d4.png
[2019050223592567.png]: /images/20220206/c3f52ec0e55f459490747822ef5ea5f8.png
[20190503000457534.png]: /images/20220206/03722600bccc46688e1cbd14e1fb8c90.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Nja2V2aW5jeWg_size_16_color_FFFFFF_t_70 1]: /images/20220206/93078bfd362641d1ae10c07718f5f223.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2Nja2V2aW5jeWg_size_16_color_FFFFFF_t_70 2]: /images/20220206/99e1a9798b8947059549c129cca8bbbd.png