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Spring控制反转IOC之注解方式.md

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Spring控制反转IOC之注解方式

一、Spring能够从classpath中自动扫描到bean

  • 注解包括：

    • @Component :除了下面的都拿它标识（组件）

    • @Respository ：持久层

    • @Service :业务层

    • @Controller :控制层

  • 对于扫描到的bean，默认id就是类名首字母小写，当然我们也可以通过value属性指定bean

    eg

    @Component//默认id是studentDao
StudentDao

@Component(value = "stu")//指定id为stu
StudentDao

  • 当在类上使用了特定注解后，还需要在配置文件中添加声明：

    eg

    <!-- base-package表示需要扫描的包及子包 -->
<context:component-scan base-package="com.edu.bean"></context:component-scan>

    • 子节点： 可以有多个(此节点有一个属性type: type的取值annotation(注解) 和assignable(具体接口或类))

      • <context:include-filter> 包含特例

      • <context:exclude-filter> 不包含特例

      eg:annotation

      ----------- exclude-filter--------------

      <context:component-scan base-package="com.edu.bean">
 <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Component"/>
</context:component-scan>

      ----------- include-filter--------------

      <context:component-scan base-package="com.edu.bean" use-default-filters="false">
 <context:include-filter type="annotation" expression="org.springframework.stereotype.Component"/>
</context:component-scan>

      eg:assignable

      ----------- exclude-filter--------------

       <context:component-scan base-package="com.edu.bean">
      <context:exclude-filter type="assignable" expression="com.edu.bean.Classroom"/>
 </context:component-scan>

      ----------- include-filter--------------

       <context:component-scan base-package="com.edu.bean" use-default-filters="false">
     <context:include-filter type="assignable" expression="com.edu.bean.Student"/>
 </context:component-scan>

二、环境配置

    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-beans</artifactId>
        <version>4.3.14.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.3.14.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.3.14.RELEASE</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-expression</artifactId>
        <version>4.3.14.RELEASE</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.16.18</version>
        <scope>provided</scope>
    </dependency>

三、应用

  • 1、@Component（组件）的使用

    • 1>javabean（Student类）

      package com.edu.bean;

import lombok.Data;
import org.springframework.stereotype.Component;

@Data
@Component//默认id是student
public class Student {
    private Integer id;
    private String name;
    private String gender;
}

    • 2>xml配置

      <context:component-scan base-package="com.edu.bean"/>

    • 3>测试

       @Test
 public void test1(){
     //1.创建ioc容器对象：
     ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring.xml");
     
     //通过id获得Student实例；com.edu.bean.Student的默认id是student
     Student student = (Student) applicationContext.getBean("student");
     
     //通过类名获得Student实例
     Student student2 = applicationContext.getBean(Student.class);
     
     System.out.println(student);
 }

    • 4>拓展

      • 指定id

        @Component(value = "stu")
或
@Component("stu")

      • @Component、@Respository、@Service、@Controller可以混用

        //@Component//默认id是student
//@Component(value = "stu")//指定id为stu
//@Component("stu")//指定id为stu
@Service//默认id是student
//@Service(value = "aa")//指定id为aa
//@Service("aa")//指定id为aa
public class Student {
    private Integer id;
    private String name;
    private String gender;
}

  • 2、<context:include-filter> 包含特例与<context:exclude-filter> 不包含特例的使用

    • javabean

      Student类

      package com.edu.bean;

import lombok.Data;
import org.springframework.stereotype.Component;

@Data
@Component
public class Student {
    private Integer id;
    private String name;
    private String gender;
}

      Classroom类

      package com.edu.bean;

import lombok.Data;
import org.springframework.stereotype.Component;

@Data
@Component
public class Classroom {
    private Integer id;
    private String name;
}

  • 2、xml配置

    • 1>xml配置之<context:include-filter>

       <context:component-scan base-package="com.edu.bean">
     <context:exclude-filter type="assignable" expression="com.edu.bean.Classroom"/>
 </context:component-scan>

    • 2>xml配置之<context:exclude-filter>

       <context:component-scan base-package="com.edu.bean" use-default-filters="false">
     <context:include-filter type="assignable" expression="com.edu.bean.Student"/>
 </context:component-scan>

  • 3、测试

     @Test
 public void testStudent(){
     ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring.xml");
     Student student = (Student)applicationContext.getBean("student");
     System.out.println(student);
 }

 @Test
 public void testStudent(){
     ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring.xml");
     Student student = (Student)applicationContext.getBean("student");
     System.out.println(student);
 }