Spring自动检测并装配bean

自动化装配bean

Spring从两个角度来实现自动化装配：
1. 组件扫描(component scanning)：spring会自动发现应用上下文中所创建的bean。
2. 自动装配(autowiring)：spring自动满足bean之间的依赖。

组件扫描和自动化装配组合在一起就能发挥出强大作用，能做到将显示配置做到最少。

1.自动扫描bean

（1）entity
厨师类：

package spring.ch2.topic7;import org.springframework.beans.factory.annotation.Value;import org.springframework.stereotype.Component;/** * Created by louyuting on 17/1/22. */@Component("jack")public class Chief {    @Value("jack")    private String name = "";    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

上面的@Component 注解后面接的属性值就是制定的bean的id值，如果不加，bean的id值就是默认的首字母小写的类名。

其实还有其他标签可以作为bean的标注：
@Component-作为构件来配置bean
@Repository-标识数据仓库
@Service-标识服务
@Controller-标识MVC的控制器
但是上面的几个标签的作用大同小异，都是标注有这么一个bean。

（2）配置文件：

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"       xmlns:aop="http://www.springframework.org/schema/aop" xmlns:util="http://www.springframework.org/schema/util"       xsi:schemaLocation="        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.0.xsd        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd        http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsd        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">    <context:component-scan base-package="spring.ch2.topic7" /></beans>

配置文件里面很简单，值添加了context:component-scan 标签，里面base-package指定了扫描组件的包。

（3）测试类：

package spring.ch2.topic7;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.ApplicationContext;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;/** * Created by louyuting on 17/1/20. */@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration(locations = {"/spring/ch2/topic7/ApplicationContext-test.xml"})public class ChiefTest {    @Autowired    private ApplicationContext applicationContext;    @Test    public void testChief(){        Chief jack = (Chief)applicationContext.getBean("jack");        System.out.println(jack.getName());    }}

（4）运行结果：

jack

说明成功注入了bean，并获取到了对象。

2.过滤器 context:include-filter

这一节我们来讨论一下过滤器的使用。
（1）entity
Person接口

package spring.ch2.topic7.filter;/** * Created by louyuting on 17/1/23. */public interface Person {}

拳击手类：

package spring.ch2.topic7.filter;import org.springframework.beans.factory.annotation.Value;/** * Created by louyuting on 17/1/23. */public class Fighter implements Person {    @Value("mike")    private String name = "";    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

厨师类：

package spring.ch2.topic7.filter;import org.springframework.beans.factory.annotation.Value;/** * Created by louyuting on 17/1/23. */public class Chief implements Person{    @Value("jack")    private String name = "";    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

在上面的类里面我们没有使用任何标记bean的注解，而且我们再配置文件里面也不会显示标记bean。

（2）配置文件：

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"       xmlns:aop="http://www.springframework.org/schema/aop" xmlns:util="http://www.springframework.org/schema/util"       xsi:schemaLocation="        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.0.xsd        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd        http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsd        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">    <context:component-scan base-package="spring.ch2.topic7" >        <context:include-filter type="assignable" expression="spring.ch2.topic7.filter.Person"/>    </context:component-scan></beans>

在配置文件里面：
（1）我们配置自动扫描 context:component-scan
（2）在自动扫描里面我们在配置context:include-filter，然后type=”assignable”，这里的意思是，Person接口所派生出来的所有类，都自动注册bean。

type的四种参数：
assignable -指定扫描某个接口派生出来的类;
annotation -指定扫描使用某个注解的类;
aspectj -指定扫描AspectJ表达式相匹配的类;
custom -指定扫描自定义的实现了org.springframework.core.type.filter.TypeFilter接口的类;
regex-指定扫描符合正则表达式的类。

（3）测试类：

package spring.ch2.topic7.filter;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.ApplicationContext;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;/** * Created by louyuting on 17/1/20. * 注入List和Set */@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration(locations = {"/spring/ch2/topic7/filter/ApplicationContext-test.xml"})public class ChiefTest {    @Autowired    private ApplicationContext applicationContext;    @Test    public void testChief(){        Chief jack = (Chief)applicationContext.getBean("chief");        System.out.println(jack.getName());        Fighter mike = (Fighter)applicationContext.getBean("fighter");        System.out.println(mike.getName());    }}

（4）运行结果：

jackmike

使用场景：上面我们只是演示了第一种，因为有些时候我们是没有源码或者一个接口派生n多实现类的情况，这种场景使用这个最为合适。

3.过滤器context:exclude-filter

这个过滤器与上一节过滤器作用相反，这个过滤器主要用于过滤掉不装配的bean.下面通过一个例子来说明。
针对第二节的例子增加一些类：MyComponent类

package spring.ch2.topic7.filter;import org.springframework.stereotype.Component;/** * Created by louyuting on 17/1/23. */@Componentpublic class MyComponent implements Person {}

在这个类里面我们标记了@Component注解，一会儿我们会使用过滤器排除这个注解的所有bean

配置文件：

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"       xmlns:aop="http://www.springframework.org/schema/aop" xmlns:util="http://www.springframework.org/schema/util"       xsi:schemaLocation="        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.0.xsd        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd        http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsd        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">    <context:component-scan base-package="spring.ch2.topic7" >        <context:include-filter type="assignable" expression="spring.ch2.topic7.filter.Person"/>        <context:exclude-filter type="annotation" expression="org.springframework.stereotype.Component" />    </context:component-scan></beans>

在配置文件里面：
（1）我们配置自动扫描context:component-scan
（2）在自动扫描里面我们在配置context:include-filter，然后type=”assignable”，这里的意思是，Person接口所派生出来的所有类，都自动注册bean
（3）还配置了context:exclude-filter，所有被注解@Component标记的类我们都不自动注册。

测试类：

package spring.ch2.topic7.filter;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.context.ApplicationContext;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;/** * Created by louyuting on 17/1/20. */@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration(locations = {"/spring/ch2/topic7/filter/ApplicationContext-test.xml"})public class ChiefTest {    @Autowired    private ApplicationContext applicationContext;    @Test    public void testChief(){        Chief jack = (Chief)applicationContext.getBean("chief");        System.out.println(jack.getName());        Fighter mike = (Fighter)applicationContext.getBean("fighter");        System.out.println(mike.getName());       System.out.println(applicationContext.containsBean("myComponent"));    }}

运行结果：
`
jack
mike
false


上面所有代码的github地址。