文章目录
2.9、实验八：p命名空间
引入p命名空间
<?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:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/util
http://www.springframework.org/schema/util/spring-util.xsd
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
引入p命名空间后，可以通过以下方式为bean的各个属性赋值
<bean id="studentSix" class="org.example.bean.Student"
p:id="1006" p:name="小明" p:clazz-ref="clazzOne" p:teacherMap-ref="teacherMap"></bean>
2.10、实验九：引入外部属性文件
①加入依赖
<!-- MySQL驱动 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.30</version>
</dependency>
<!-- 数据源 -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.2.15</version>
</dependency>
②创建外部属性文件
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jdbc.user=root
jdbc.password=123456
jdbc.url=jdbc:mysql://localhost:3306/ssm?serverTimezone=UTC
jdbc.driver=com.mysql.cj.jdbc.Driver
③引入属性文件
引入context 名称空间
<?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">
</beans>
<!-- 引入外部属性文件 -->
<context:property-placeholder location="classpath:jdbc.properties"/>
注意：在使用 <context:property-placeholder> 元素加载外包配置文件功能前，首先需要在 XML 配置的一级标签 <beans> 中添加 context 相关的约束。
④配置bean
<bean id="druidDataSource" class="com.alibaba.druid.pool.DruidDataSource">
<property name="url" value="${jdbc.url}"/>
<property name="driverClassName" value="${jdbc.driver}"/>
<property name="username" value="${jdbc.user}"/>
<property name="password" value="${jdbc.password}"/>
</bean>
⑤测试
@Test
public void testDataSource() throws SQLException {
ApplicationContext ac = new ClassPathXmlApplicationContext("spring-datasource.xml");
DataSource dataSource = ac.getBean(DataSource.class);
Connection connection = dataSource.getConnection();
System.out.println(connection);
}
2.11、实验十：bean的作用域
①概念
在Spring中可以通过配置bean标签的scope属性来指定bean的作用域范围，各取值含义参加下表：
如果是在WebApplicationContext环境下还会有另外几个作用域（但不常用）：
②创建类User
package org.example.bean;
public class User {
private Integer id;
private String username;
private String password;
private Integer age;
public User() {
}
public User(Integer id, String username, String password, Integer age) {
this.id = id;
this.username = username;
this.password = password;
this.age = age;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
", age=" + age +
'}';
}
}
③配置bean
<!-- scope属性：取值singleton（默认值），bean在IOC容器中只有一个实例，IOC容器初始化时创建对象 -->
<!-- scope属性：取值prototype，bean在IOC容器中可以有多个实例，getBean()时创建对象 -->
<bean class="org.example.bean.User" scope="prototype"></bean>
④测试
@Test
public void testBeanScope(){
ApplicationContext ac = new ClassPathXmlApplicationContext("spring-scope.xml");
User user1 = ac.getBean(User.class);
User user2 = ac.getBean(User.class);
System.out.println(user1==user2);
}
2.12、实验十一：bean生命周期
①具体的生命周期过程
-
1、bean对象创建（调用无参构造器）
-
2、给bean对象设置属性
-
3、bean的后置处理器（初始化之前）
-
4、bean对象初始化（需在配置bean时指定初始化方法）
-
5、bean的后置处理器（初始化之后）
-
6、bean对象就绪可以使用
-
7、bean对象销毁（需在配置bean时指定销毁方法）
-
8、IOC容器关闭
②修改类User
public class User {
private Integer id;
private String username;
private String password;
private Integer age;
public User() {
System.out.println("生命周期：1、创建对象");
}
public User(Integer id, String username, String password, Integer age) {
this.id = id;
this.username = username;
this.password = password;
this.age = age;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
System.out.println("生命周期：2、依赖注入");
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public Integer getAge() {
return age;
}
public void setAge(Integer age) {
this.age = age;
}
public void initMethod(){
System.out.println("生命周期：3、初始化");
}
public void destroyMethod(){
System.out.println("生命周期：5、销毁");
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
", age=" + age +
'}';
}
}
③配置bean
<!-- 使用init-method属性指定初始化方法 -->
<!-- 使用destroy-method属性指定销毁方法 -->
<bean class="org.example.bean.User" scope="prototype" init-method="initMethod" destroy-method="destroyMethod">
<property name="id" value="1001"></property>
<property name="username" value="admin"></property>
<property name="password" value="123456"></property>
<property name="age" value="23"></property>
</bean>
④测试
@Test
public void testLife(){
ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("spring-lifecycle.xml");
User bean = ac.getBean(User.class);
System.out.println("生命周期：4、通过IOC容器获取bean并使用");
ac.close();
}
⑤bean的后置处理器
bean的后置处理器会在生命周期的初始化前后添加额外的操作，需要实现BeanPostProcessor接口，且配置到IOC容器中，需要注意的是，bean后置处理器不是单独针对某一个bean生效，而是针对IOC容器中所有bean都会执行
创建bean的后置处理器：
package org.example.process;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;
public class MyBeanProcessor implements BeanPostProcessor {
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
System.out.println("☆☆☆" + beanName + " = " + bean);
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
System.out.println("★★★" + beanName + " = " + bean);
return bean;
}
}
在IOC容器中配置后置处理器：
<!-- bean的后置处理器要放入IOC容器才能生效 -->
<bean id="myBeanProcessor" class="org.example.process.MyBeanProcessor"/>
2.13、实验十二：FactoryBean
①简介
FactoryBean是Spring提供的一种整合第三方框架的常用机制。和普通的bean不同，配置一个FactoryBean类型的bean，在获取bean的时候得到的并不是class属性中配置的这个类的对象，而是getObject()方法的返回值。通过这种机制，Spring可以帮我们把复杂组件创建的详细过程和繁琐细节都屏蔽起来，只把最简洁的使用界面展示给我们。
整合Mybatis时，Spring就是通过FactoryBean机制来帮我们创建SqlSessionFactory对象的。
/*
* Copyright 2002-2020 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.beans.factory;
import org.springframework.lang.Nullable;
/**
* Interface to be implemented by objects used within a {@link BeanFactory} which
* are themselves factories for individual objects. If a bean implements this
* interface, it is used as a factory for an object to expose, not directly as a
* bean instance that will be exposed itself.
*
* <p><b>NB: A bean that implements this interface cannot be used as a normal bean.</b>
* A FactoryBean is defined in a bean style, but the object exposed for bean
* references ({@link #getObject()}) is always the object that it creates.
*
* <p>FactoryBeans can support singletons and prototypes, and can either create
* objects lazily on demand or eagerly on startup. The {@link SmartFactoryBean}
* interface allows for exposing more fine-grained behavioral metadata.
*
* <p>This interface is heavily used within the framework itself, for example for
* the AOP {@link org.springframework.aop.framework.ProxyFactoryBean} or the
* {@link org.springframework.jndi.JndiObjectFactoryBean}. It can be used for
* custom components as well; however, this is only common for infrastructure code.
*
* <p><b>{@code FactoryBean} is a programmatic contract. Implementations are not
* supposed to rely on annotation-driven injection or other reflective facilities.</b>
* {@link #getObjectType()} {@link #getObject()} invocations may arrive early in the
* bootstrap process, even ahead of any post-processor setup. If you need access to
* other beans, implement {@link BeanFactoryAware} and obtain them programmatically.
*
* <p><b>The container is only responsible for managing the lifecycle of the FactoryBean
* instance, not the lifecycle of the objects created by the FactoryBean.</b> Therefore,
* a destroy method on an exposed bean object (such as {@link java.io.Closeable#close()}
* will <i>not</i> be called automatically. Instead, a FactoryBean should implement
* {@link DisposableBean} and delegate any such close call to the underlying object.
*
* <p>Finally, FactoryBean objects participate in the containing BeanFactory's
* synchronization of bean creation. There is usually no need for internal
* synchronization other than for purposes of lazy initialization within the
* FactoryBean itself (or the like).
*
* @author Rod Johnson
* @author Juergen Hoeller
* @since 08.03.2003
* @param <T> the bean type
* @see org.springframework.beans.factory.BeanFactory
* @see org.springframework.aop.framework.ProxyFactoryBean
* @see org.springframework.jndi.JndiObjectFactoryBean
*/
public interface FactoryBean<T> {
/**
* The name of an attribute that can be
* {@link org.springframework.core.AttributeAccessor#setAttribute set} on a
* {@link org.springframework.beans.factory.config.BeanDefinition} so that
* factory beans can signal their object type when it can't be deduced from
* the factory bean class.
* @since 5.2
*/
String OBJECT_TYPE_ATTRIBUTE = "factoryBeanObjectType";
/**
* Return an instance (possibly shared or independent) of the object
* managed by this factory.
* <p>As with a {@link BeanFactory}, this allows support for both the
* Singleton and Prototype design pattern.
* <p>If this FactoryBean is not fully initialized yet at the time of
* the call (for example because it is involved in a circular reference),
* throw a corresponding {@link FactoryBeanNotInitializedException}.
* <p>As of Spring 2.0, FactoryBeans are allowed to return {@code null}
* objects. The factory will consider this as normal value to be used; it
* will not throw a FactoryBeanNotInitializedException in this case anymore.
* FactoryBean implementations are encouraged to throw
* FactoryBeanNotInitializedException themselves now, as appropriate.
* @return an instance of the bean (can be {@code null})
* @throws Exception in case of creation errors
* @see FactoryBeanNotInitializedException
*/
@Nullable
T getObject() throws Exception;
/**
* Return the type of object that this FactoryBean creates,
* or {@code null} if not known in advance.
* <p>This allows one to check for specific types of beans without
* instantiating objects, for example on autowiring.
* <p>In the case of implementations that are creating a singleton object,
* this method should try to avoid singleton creation as far as possible;
* it should rather estimate the type in advance.
* For prototypes, returning a meaningful type here is advisable too.
* <p>This method can be called <i>before</i> this FactoryBean has
* been fully initialized. It must not rely on state created during
* initialization; of course, it can still use such state if available.
* <p><b>NOTE:</b> Autowiring will simply ignore FactoryBeans that return
* {@code null} here. Therefore it is highly recommended to implement
* this method properly, using the current state of the FactoryBean.
* @return the type of object that this FactoryBean creates,
* or {@code null} if not known at the time of the call
* @see ListableBeanFactory#getBeansOfType
*/
@Nullable
Class<?> getObjectType();
/**
* Is the object managed by this factory a singleton? That is,
* will {@link #getObject()} always return the same object
* (a reference that can be cached)?
* <p><b>NOTE:</b> If a FactoryBean indicates to hold a singleton object,
* the object returned from {@code getObject()} might get cached
* by the owning BeanFactory. Hence, do not return {@code true}
* unless the FactoryBean always exposes the same reference.
* <p>The singleton status of the FactoryBean itself will generally
* be provided by the owning BeanFactory; usually, it has to be
* defined as singleton there.
* <p><b>NOTE:</b> This method returning {@code false} does not
* necessarily indicate that returned objects are independent instances.
* An implementation of the extended {@link SmartFactoryBean} interface
* may explicitly indicate independent instances through its
* {@link SmartFactoryBean#isPrototype()} method. Plain {@link FactoryBean}
* implementations which do not implement this extended interface are
* simply assumed to always return independent instances if the
* {@code isSingleton()} implementation returns {@code false}.
* <p>The default implementation returns {@code true}, since a
* {@code FactoryBean} typically manages a singleton instance.
* @return whether the exposed object is a singleton
* @see #getObject()
* @see SmartFactoryBean#isPrototype()
*/
default boolean isSingleton() {
return true;
}
}
②创建类UserFactoryBean
package org.example.bean;
public class UserFactoryBean implements FactoryBean<User> {
@Override
public User getObject() throws Exception {
return new User();
}
@Override
public Class<?> getObjectType() {
return User.class;
}
}
③配置bean
<bean id="user" class="org.example.bean.UserFactoryBean"></bean>
④测试
@Test
public void testUserFactoryBean(){
//获取IOC容器
ApplicationContext ac = new ClassPathXmlApplicationContext("spring-factorybean.xml");
User user = (User) ac.getBean("user");
System.out.println(user);
}
2.14、实验十三：基于xml自动装配
①场景模拟
创建类UserController
package org.example.autowire.controller;
public class UserController {
private UserService userService;
public void setUserService(UserService userService) {
this.userService = userService;
}
public void saveUser(){
userService.saveUser();
}
}
创建接口UserService
package org.example.autowire.service;
public interface UserService {
void saveUser();
}
创建类UserServiceImpl实现接口UserService
package org.example.autowire.service.impl;
public class UserServiceImpl implements UserService {
private UserDao userDao;
public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
@Override
public void saveUser() {
userDao.saveUser();
}
}
创建接口UserDao
package org.example.autowire.dao;
public interface UserDao {
void saveUser();
}
创建类UserDaoImpl实现接口UserDao
package org.example.autowire.dao.impl;
public class UserDaoImpl implements UserDao {
@Override
public void saveUser() {
System.out.println("保存成功");
}
}
②配置bean
<bean id="userController" class="org.example.autowire.controller.UserController" autowire="byType"></bean>
<bean id="userService" class="org.example.autowire.service.impl.UserServiceImpl" autowire="byType"></bean>
<bean id="userDao" class="org.example.autowire.dao.impl.UserDaoImpl"></bean>
<bean id="userController" class="org.example.autowire.controller.UserController" autowire="byName"></bean>
<bean id="userService" class="org.example.autowire.service.impl.UserServiceImpl" autowire="byName"></bean>
<bean id="userServiceImpl" class="org.example.autowire.service.impl.UserServiceImpl" autowire="byName"></bean>
<bean id="userDao" class="org.example.autowire.dao.impl.UserDaoImpl"></bean>
<bean id="userDaoImpl" class="org.example.autowire.dao.impl.UserDaoImpl"></bean>
③测试
@Test
public void testAutoWireByXML(){
ApplicationContext ac = new ClassPathXmlApplicationContext("autowire-xml.xml");
UserController userController = ac.getBean(UserController.class);
userController.saveUser();
}
3、基于注解管理Bean
从 Java 5 开始，Java 增加了对注解（Annotation）的支持，它是代码中的一种特殊标记，可以在编译、类加载和运行时被读取，执行相应的处理。开发人员可以通过注解在不改变原有代码和逻辑的情况下，在源代码中嵌入补充信息。
Spring 从 2.5 版本开始提供了对注解技术的全面支持，我们可以使用注解来实现自动装配，简化 Spring 的 XML 配置。
Spring 通过注解实现自动装配的步骤如下：
- 引入依赖
- 开启组件扫描
- 使用注解定义 Bean
- 依赖注入
3.1、搭建子模块spring6-ioc-annotation
①搭建模块
搭建方式如：spring6-ioc-xml
②引入配置文件
引入spring-ioc-xml模块日志log4j2.xml
③添加依赖
<dependencies>
<!--spring context依赖-->
<!--当你引入Spring Context依赖之后，表示将Spring的基础依赖引入了-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>6.0.3</version>
</dependency>
<!--junit5测试-->
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-api</artifactId>
</dependency>
<!--log4j2的依赖-->
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-core</artifactId>
<version>2.19.0</version>
</dependency>
<dependency>
<groupId>org.apache.logging.log4j</groupId>
<artifactId>log4j-slf4j2-impl</artifactId>
<version>2.19.0</version>
</dependency>
</dependencies>
3.2、开启组件扫描
Spring 默认不使用注解装配 Bean，因此我们需要在 Spring 的 XML 配置中，通过 <context:component-scan> 元素开启 Spring Beans的自动扫描功能。开启此功能后，Spring 会自动从扫描指定的包（base-package 属性设置）及其子包下的所有类，如果类上使用了 @Component 注解，就将该类装配到容器中。
<?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-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<!--开启组件扫描功能-->
<context:component-scan base-package="org.example"></context:component-scan>
</beans>
注意：在使用 <context:component-scan> 元素开启自动扫描功能前，首先需要在 XML 配置的一级标签 <beans> 中添加 context 相关的约束。
情况一：最基本的扫描方式
<context:component-scan base-package="org.example">
</context:component-scan>
情况二：指定要排除的组件
<context:component-scan base-package="org.example">
<!-- context:exclude-filter标签：指定排除规则 -->
<!--
type：设置排除或包含的依据
type="annotation"，根据注解排除，expression中设置要排除的注解的全类名
type="assignable"，根据类型排除，expression中设置要排除的类型的全类名
-->
<context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
<!--<context:exclude-filter type="assignable" expression="org.example.controller.UserController"/>-->
</context:component-scan>
情况三：仅扫描指定组件
<context:component-scan base-package="org.example" use-default-filters="false">
<!-- context:include-filter标签：指定在原有扫描规则的基础上追加的规则 -->
<!-- use-default-filters属性：取值false表示关闭默认扫描规则 -->
<!-- 此时必须设置use-default-filters="false"，因为默认规则即扫描指定包下所有类 -->
<!--
type：设置排除或包含的依据
type="annotation"，根据注解排除，expression中设置要排除的注解的全类名
type="assignable"，根据类型排除，expression中设置要排除的类型的全类名
-->
<context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/>
<!--<context:include-filter type="assignable" expression="org.example.controller.UserController"/>-->
</context:component-scan>
3.3、使用注解定义 Bean
Spring 提供了以下多个注解，这些注解可以直接标注在 Java 类上，将它们定义成 Spring Bean。
3.4、实验一：@Autowired注入
单独使用@Autowired注解，默认根据类型装配。【默认是byType】
查看源码：
package org.springframework.beans.factory.annotation;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target({ElementType.CONSTRUCTOR, ElementType.METHOD, ElementType.PARAMETER, ElementType.FIELD, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Autowired {
boolean required() default true;
}
源码中有两处需要注意：
-
第一处：该注解可以标注在哪里？
-
- 构造方法上
- 方法上
- 形参上
- 属性上
- 注解上
-
第二处：该注解有一个
required属性，默认值是true，表示在注入的时候要求被注入的Bean必须是存在的，如果不存在则报错。如果required属性设置为false，表示注入的Bean存在或者不存在都没关系，存在的话就注入，不存在的话，也不报错。
①场景一：属性注入
创建UserDao接口
package org.example.dao;
public interface UserDao {
public void print();
}
创建UserDaoImpl实现
package org.example.dao.impl;
import org.example.dao.UserDao;
import org.springframework.stereotype.Repository;
@Repository
public class UserDaoImpl implements UserDao {
@Override
public void print() {
System.out.println("Dao层执行结束");
}
}
创建UserService接口
package org.example.spring6.service;
public interface UserService {
public void out();
}
创建UserServiceImpl实现类
package org.example.spring6.service.impl;
import org.example.spring6.dao.UserDao;
import org.example.spring6.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl implements UserService {
@Autowired
private UserDao userDao;
@Override
public void out() {
userDao.print();
System.out.println("Service层执行结束");
}
}
创建UserController类
package org.exampleu.spring6.controller;
import org.example.spring6.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
@Controller
public class UserController {
@Autowired
private UserService userService;
public void out() {
userService.out();
System.out.println("Controller层执行结束。");
}
}
测试一
package org.example.spring6.bean;
import org.example.spring6.controller.UserController;
import org.junit.jupiter.api.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class UserTest {
private Logger logger = LoggerFactory.getLogger(UserTest.class);
@Test
public void testAnnotation(){
ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");
UserController userController = context.getBean("userController", UserController.class);
userController.out();
logger.info("执行成功");
}
}
以上构造方法和setter方法都没有提供，经过测试，仍然可以注入成功。
②场景二：set注入
修改UserServiceImpl类
package org.example.service.impl;
import org.example.dao.UserDao;
import org.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl implements UserService {
private UserDao userDao;
@Autowired
public void setUserDao(UserDao userDao) {
this.userDao = userDao;
}
@Override
public void out() {
userDao.print();
System.out.println("Service层执行结束");
}
}
修改UserController类
package org.example.controller;
import org.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
@Controller
public class UserController {
private UserService userService;
@Autowired
public void setUserService(UserService userService) {
this.userService = userService;
}
public void out() {
userService.out();
System.out.println("Controller层执行结束。");
}
}
测试：成功调用
③场景三：构造方法注入
修改UserServiceImpl类
package org.example.service.impl;
import org.example.dao.UserDao;
import org.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl implements UserService {
private UserDao userDao;
@Autowired
public UserServiceImpl(UserDao userDao) {
this.userDao = userDao;
}
@Override
public void out() {
userDao.print();
System.out.println("Service层执行结束");
}
}
修改UserController类
package org.example.controller;
import org.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
@Controller
public class UserController {
private UserService userService;
@Autowired
public UserController(UserService userService) {
this.userService = userService;
}
public void out() {
userService.out();
System.out.println("Controller层执行结束。");
}
}
测试：成功调用
④场景四：形参上注入
修改UserServiceImpl类
package org.example.service.impl;
import org.example.spring6.dao.UserDao;
import org.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl implements UserService {
private UserDao userDao;
public UserServiceImpl(@Autowired UserDao userDao) {
this.userDao = userDao;
}
@Override
public void out() {
userDao.print();
System.out.println("Service层执行结束");
}
}
修改UserController类
package org.example.controller;
import org.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
@Controller
public class UserController {
private UserService userService;
public UserController(@Autowired UserService userService) {
this.userService = userService;
}
public void out() {
userService.out();
System.out.println("Controller层执行结束。");
}
}
测试：成功调用
⑤场景五：只有一个构造函数，无注解
修改UserServiceImpl类
package org.example.service.impl;
import org.example.dao.UserDao;
import org.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl implements UserService {
@Autowired
private UserDao userDao;
public UserServiceImpl(UserDao userDao) {
this.userDao = userDao;
}
@Override
public void out() {
userDao.print();
System.out.println("Service层执行结束");
}
}
测试通过
当有参数的构造方法只有一个时，@Autowired注解可以省略。
说明：有多个构造方法时呢？大家可以测试（再添加一个无参构造函数），测试报错
⑥场景六：@Autowired注解和@Qualifier注解联合
添加dao层实现
package org.example.dao.impl;
import org.example.dao.UserDao;
import org.springframework.stereotype.Repository;
@Repository
public class UserDaoRedisImpl implements UserDao {
@Override
public void print() {
System.out.println("Redis Dao层执行结束");
}
}
测试：测试异常
错误信息中说：不能装配，UserDao这个Bean的数量等于2
怎么解决这个问题呢？当然要byName，根据名称进行装配了。
修改UserServiceImpl类
package org.example.service.impl;
import org.example.dao.UserDao;
import org.example.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl implements UserService {
@Autowired
@Qualifier("userDaoImpl") // 指定bean的名字
private UserDao userDao;
@Override
public void out() {
userDao.print();
System.out.println("Service层执行结束");
}
}
总结
@Autowired注解可以出现在：属性上、构造方法上、构造方法的参数上、setter方法上。- 当带参数的构造方法只有一个，@Autowired注解可以省略。（）
- @Autowired注解默认根据类型注入。如果要根据名称注入的话，需要配合
@Qualifier注解一起使用。
3.5、实验二：@Resource注入
@Resource注解也可以完成属性注入。那它和@Autowired注解有什么区别？
@Resource注解是JDK扩展包中的，也就是说属于JDK的一部分。所以该注解是标准注解，更加具有通用性。(JSR-250标准中制定的注解类型。JSR是Java规范提案。)- @Autowired注解是Spring框架自己的。
- @Resource注解默认根据名称装配byName，未指定name时，使用属性名作为name。通过name找不到的话会自动启动通过类型byType装配。
- @Autowired注解默认根据类型装配byType，如果想根据名称装配，需要配合@Qualifier注解一起用。
- @Resource注解用在属性上、setter方法上。
- @Autowired注解用在属性上、setter方法上、构造方法上、构造方法参数上。
@Resource注解属于JDK扩展包，所以不在JDK当中，需要额外引入以下依赖：【如果是JDK8的话不需要额外引入依赖。高于JDK11或低于JDK8需要引入以下依赖。】
<dependency>
<groupId>jakarta.annotation</groupId>
<artifactId>jakarta.annotation-api</artifactId>
<version>2.1.1</version>
</dependency>
源码：
package jakarta.annotation;
import java.lang.annotation.ElementType;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
@Target({ElementType.TYPE, ElementType.FIELD, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Repeatable(Resources.class)
public @interface Resource {
String name() default "";
String lookup() default "";
Class<?> type() default Object.class;
Resource.AuthenticationType authenticationType() default Resource.AuthenticationType.CONTAINER;
boolean shareable() default true;
String mappedName() default "";
String description() default "";
public static enum AuthenticationType {
CONTAINER,
APPLICATION;
private AuthenticationType() {
}
}
}
①场景一：根据name注入
修改UserDaoImpl类
package org.example.dao.impl;
import org.example.dao.UserDao;
import org.springframework.stereotype.Repository;
@Repository("myUserDao")
public class UserDaoImpl implements UserDao {
@Override
public void print() {
System.out.println("Dao层执行结束");
}
}
修改UserServiceImpl类
package org.example.service.impl;
import org.example.dao.UserDao;
import org.example.service.UserService;
import jakarta.annotation.Resource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl implements UserService {
@Resource(name = "myUserDao")
private UserDao myUserDao;
@Override
public void out() {
myUserDao.print();
System.out.println("Service层执行结束");
}
}
测试通过
②场景二：name未知注入
修改UserDaoImpl类
package org.example.dao.impl;
import org.example.dao.UserDao;
import org.springframework.stereotype.Repository;
@Repository("myUserDao")
public class UserDaoImpl implements UserDao {
@Override
public void print() {
System.out.println("Dao层执行结束");
}
}
修改UserServiceImpl类
package org.example.service.impl;
import org.example.dao.UserDao;
import org.example.service.UserService;
import jakarta.annotation.Resource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl implements UserService {
@Resource
private UserDao myUserDao;
@Override
public void out() {
myUserDao.print();
System.out.println("Service层执行结束");
}
}
测试通过
当@Resource注解使用时没有指定name的时候，还是根据name进行查找，这个name是 属性名 。
③场景三 其他情况
修改UserServiceImpl类，userDao1属性名不存在
package org.example.service.impl;
import org.example.dao.UserDao;
import org.example.service.UserService;
import jakarta.annotation.Resource;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Service;
@Service
public class UserServiceImpl implements UserService {
@Resource
private UserDao userDao1;
@Override
public void out() {
userDao1.print();
System.out.println("Service层执行结束");
}
}
测试异常
根据异常信息得知：显然当通过name找不到的时候，自然会启动byType进行注入，以上的错误是因为UserDao接口下有两个实现类导致的。所以根据类型注入就会报错。
@Resource的set注入可以自行测试
总结：
@Resource注解：默认byName注入，没有指定name时把属性名当做name，根据name找不到时，才会byType注入。byType注入时，某种类型的Bean只能有一个
3.6、Spring全注解开发
全注解开发就是不再使用spring配置文件了，写一个配置类来代替配置文件。
package org.example.config;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
@Configuration
//@ComponentScan({"org.example.controller", "org.example.service","org.example.dao"})
@ComponentScan("org.example")
public class Spring6Config {
}
测试类
@Test
public void testAllAnnotation(){
ApplicationContext context = new AnnotationConfigApplicationContext(Spring6Config.class);
UserController userController = context.getBean("userController", UserController.class);
userController.out();
logger.info("执行成功");
}