注解的使用
引入外部的properties文件
首先创建配置文件
创建beans6.xml
<?xml version="1.0" encoding="UTF-8"?><beans xmlns="/schema/beans"xmlns:xsi="/2001/XMLSchema-instance"xsi:schemaLocation="/schema/beans /schema/beans/spring-beans.xsd"><bean id="druid" class="com.alibaba.druid.pool.DruidDataSource"><property name="driverClassName" value="com.mysql.jdbc.Driver"></property><property name="url" value="jdbc:mysql://localhost:3306/maclu"></property><property name="username" value="root"></property><property name="password" value="123456"></property></bean></beans>
测试
@Testpublic void Tses15(){ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beans6.xml");DruidDataSource druid = context.getBean("druid", DruidDataSource.class);DruidPooledConnection connection = null;try {connection = druid.getConnection();System.out.println(connection);} catch (SQLException e) {e.printStackTrace();}finally {try {connection.close();} catch (SQLException e) {e.printStackTrace();}}}
结果
或者先添加druid的pom依赖
<!-- /artifact/com.alibaba/druid --><dependency><groupId>com.alibaba</groupId><artifactId>druid</artifactId><version>1.2.6</version></dependency>
创建beans7.xml
<?xml version="1.0" encoding="UTF-8"?><beans xmlns="/schema/beans"xmlns:xsi="/2001/XMLSchema-instance"xmlns:context="/schema/context"xsi:schemaLocation="/schema/beans /schema/beans/spring-beans.xsd /schema/context /schema/context/spring-context.xsd"><context:property-placeholder location="classpath:db.properties"></context:property-placeholder><bean id="druid" class="com.alibaba.druid.pool.DruidDataSource"><property name="driverClassName" value="${jdbc.driverClassName}"></property><property name="url" value="${jdbc.url}"></property><property name="username" value="${jdbc.username}"></property><property name="password" value="${jdbc.password}"></property></bean></beans>
结果
依赖注入
1）Spring配置文件引入context约束
<?xml version="1.0" encoding="UTF-8"?><beans xmlns="/schema/beans"xmlns:xsi="/2001/XMLSchema-instance"xmlns:context="/schema/context"xmlns:aop="/schema/aop"xmlns:c="/schema/c"xmlns:util="/schema/util"xmlns:p="/schema/p"xsi:schemaLocation="/schema/beans /schema/beans/spring-beans.xsd/schema/context /schema/context/spring-context-4.3.xsd/schema/aop /schema/aop/spring-aop-4.3.xsd/schema/util /schema/util/spring-util-4.3.xsd"></beans>
2）Spring配置文件中开启注解扫描
<?xml version="1.0" encoding="UTF-8"?><beans xmlns="/schema/beans"xmlns:xsi="/2001/XMLSchema-instance"xmlns:context="/schema/context"xmlns:aop="/schema/aop"xmlns:c="/schema/c"xmlns:util="/schema/util"xmlns:p="/schema/p"xsi:schemaLocation="/schema/beans /schema/beans/spring-beans.xsd/schema/context /schema/context/spring-context-4.3.xsd/schema/aop /schema/aop/spring-aop-4.3.xsd/schema/util /schema/util/spring-util-4.3.xsd"><context:component-scan base-package="com.cqucc" /></beans>
在classpath中的扫描组件：component-scan，他能够在classpath中自动扫描，自动检查和实例化具有特定注解的组件。
特定组件包括
@Component ：组件通用注解，标识一个受Spring管理的组件@Controller ：常用于对表现标注@Service：常用于对服务层（业务层）标注@Repository：常用于对持久层标注
@Component、@Controller、@Service和@Repository功能一样，可以互换，我们使用不同注解主要为了区分被注解的类处在不同的业务层，使逻辑更加清晰。
它们使用方法：
（1）标注在类上
（2）@Component("name")等于@Component(value="user")
（3）@Component相当于@Component("className")
3）案例
Users类
package com.cqucc.pojo;import org.ponent;@Componentpublic class Users {private Integer userid;private String usernama;private String password;public Users (){System.out.println("这是无参构造方法");}public Users(Integer userid, String usernama, String password) {System.out.println("这是有参构造方法");this.userid = userid;this.usernama = usernama;this.password = password;}public void say(){System.out.println("hello");}public String getPassword() {return password;}public void setPassword(String password) {this.password = password;}public String getUsernama() {return usernama;}public void setUsernama(String usernama) {this.usernama = usernama;}public Integer getUserid() {return userid;}public void setUserid(Integer userid) {this.userid = userid;}@Overridepublic String toString() {return "Users{" +"userid=" + userid +", usernama='" + usernama + '\'' +", password='" + password + '\'' +'}';}}
编写测试类：
@Testpublic void Tses(){ApplicationContext act = new ClassPathXmlApplicationContext("beans8.xml");Users users = act.getBean(Users.class);Users users2 = act.getBean("users",Users.class);System.out.println(users);System.out.println(users2);}
测试结果
注:在注解中value属性值可以省略不写，
@Testpublic void Tses17(){ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beans8.xml");DeptAction deptAction = context.getBean(DeptAction.class);System.out.println(deptAction);deptAction.show();DeptService deptService = context.getBean(DeptService.class);System.out.println(deptService);deptService.show();DeptDao deptDao = context.getBean(DeptDao.class);System.out.println(deptDao);}
，首字母小写
4）属性注入
4.1@Autowired
自动注入的方式进行注入，默认根据类的名称来进行装配
DeptDao类
package com.cqucc.dao;import org.springframework.stereotype.Repository;@Repositorypublic class DeptDao {public void show(){System.out.println("dept执行了");}}
DeptService 类
package com.cqucc.service;import com.cqucc.dao.DeptDao;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Service;@Servicepublic class DeptService {@Autowiredprivate DeptDao deptDao;public void show(){System.out.println("service执行了");deptDao.show();}}
DeptAction 类
package com.cqucc.action;import com.cqucc.service.DeptService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Controller;@Controllerpublic class DeptAction {@Autowiredprivate DeptService deptService;public void show(){System.out.println("action执行了");deptService.show();}}
测试类
@Testpublic void Tses17(){ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beans8.xml");DeptAction deptAction = context.getBean(DeptAction.class);System.out.println(deptAction);deptAction.show();DeptService deptService = context.getBean(DeptService.class);System.out.println(deptService);deptService.show();DeptDao deptDao = context.getBean(DeptDao.class);System.out.println(deptDao);}
测试结果
@Autowired注意事项：
默认情况下，所有使用@Autowired注解的属性都需要被设置。当Spring找不到匹配的bean装配属性时，会抛出异常。
如去掉DeptAction 类中的的@Autowired时
package com.cqucc.action;import com.cqucc.service.DeptService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Controller;@Controllerpublic class DeptAction {private DeptService deptService;public void show(){System.out.println("action执行了");deptService.show();}}//测试方法@Testpublic void Tses17(){ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("beans8.xml");DeptAction deptAction = context.getBean(DeptAction.class);System.out.println(deptAction);deptAction.show();}
测试结果
4.2 @Qualifier
@Autowired是按照类型进行匹配，如果当前@Autowired标注的依赖在容器中只能找到一个实例一致对应的话，那还好。可是，要是能够同时找到多个或者同一类型的对象实例，那该怎么办？可以使用@Qualifier对依赖注入的条件做进一步限定。如下
定义接口
package com.cqucc.dao;public interface DeptDaoInter {public void show();}
实现接口的两个类
package com.cqucc.dao.Impl;import com.cqucc.dao.DeptDaoInter;import org.springframework.stereotype.Repository;@Repositorypublic class DeptDao implements DeptDaoInter {public void show(){System.out.println("dept执行了");}}
package com.cqucc.dao.Impl;import com.cqucc.dao.DeptDaoInter;import org.springframework.stereotype.Repository;@Repositorypublic class DeptDao1 implements DeptDaoInter {public void show(){System.out.println("dept1执行了");}}
测试类
@Testpublic void test18(){ApplicationContext context = new ClassPathXmlApplicationContext("beans9.xml");DeptService deptService = context.getBean(DeptService.class);System.out.println(deptService);}
结果：
当添加@Qualifier（"deptDao1"）后
package com.cqucc.service;import com.cqucc.dao.DeptDaoInter;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.annotation.Qualifier;import org.springframework.stereotype.Service;@Servicepublic class DeptService {@Autowired@Qualifier("deptDao1")private DeptDaoInter deptDaoInter;public void show(){System.out.println("service执行了");deptDaoInter.show();}}
测试结果
4.3 @Resource
@Resource（name = "deptDao1"）相当于@Autowired+@Qualifier（"name"）
package com.cqucc.service;import com.cqucc.dao.DeptDaoInter;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.annotation.Qualifier;import org.springframework.stereotype.Service;import javax.annotation.Resource;@Servicepublic class DeptService {// @Autowired// @Qualifier("deptDao1")@Resource(name = "deptDao1")private DeptDaoInter deptDaoInter;public void show(){System.out.println("service执行了");deptDaoInter.show();}}
测试结果
5)包含（不包含）组件
<context:component-scan>提供了两个子标签
<context:include-filter><context:exclude-filter>
在说明这两个子标签前，先说一下<context:component-scan>有一个use-default-filters属性，该属性默认为true，这就意味着会扫描指定包下的全部的标有Spring注解的类，并注册成bean。也就是@Component，@Controller，@Service，@Reposity等。所以如果仅仅是在配置文件中这么写
<context:component-scan base-package="com.*"/>
use-default-filter此时为true那么会对base-package包或者子包下的所有的进行java类进行扫描,并把匹配的java类注册成bean。
可以发现这种扫描的粒度有点太大，如果你只想扫描指定包下面的Controller，该怎么办？此时子标签<context:incluce-filter>就起到了勇武之地。如下所示
<context:component-scan base-package="com.cqucc" use-default-filters="false"><context:include-filter type="annotation" expression="org.springframework.stereotype.Controller"/></context:component-scan>
这样就会只扫描base-package包或者子包下所有@Controller下的java类，并注册成bean。
去访问除了@Controller以为的类会包下面的错误
如果不想扫描指定包下面的Controller时，需要使用<context:exclude-filter>标签
<context:component-scan base-package="com.cqucc"><context:exclude-filter type="annotation" expression="org.springframework.stereotype.Controller"/></context:component-scan>
去访问@Controller以为的类会包下面的错误
6)无配置注解
@Configuration用于定义配置类，可替换xml配置文件，被注解的类内部包含有一个或多个被@Bean注解的方法，这些方法将会被AnnotationConfigApplicationContext或AnnotationConfigWebApplicationContext类进行扫描，并用于构建bean定义，初始化Spring容器。
注意：@Configuration注解的配置类有如下要求：
@Configuration不可以是final类型；
@Configuration不可以是匿名类；
嵌套的configuration必须是静态类。
如下:
package com.cqucc.config;import org.springframework.ponentScan;import org.springframework.context.annotation.Configuration;@Configuration@ComponentScan(basePackages = {"com.cqucc"})public class SpringConfig {public SpringConfig(){System.out.println("容器启动初始化...");}}
测试类
@Testpublic void test20(){ApplicationContext context = new AnnotationConfigApplicationContext(SpringConfig.class);DeptAction action = context.getBean(DeptAction.class);System.out.println(action);action.show();}
结果
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