Spring Auto Scanning

30 Aug 2015

Reading time ~1 minute

一、一般的bean

1、CustomerDAO.java

package com.mkyong.customer.dao;

public class CustomerDAO 
{
    @Override
    public String toString() {
        return "Hello , This is CustomerDAO";
    }	
}

2、CustomerService.java

package com.mkyong.customer.services;

import com.mkyong.customer.dao.CustomerDAO;

public class CustomerService 
{
    CustomerDAO customerDAO;

    public void setCustomerDAO(CustomerDAO customerDAO) {
        this.customerDAO = customerDAO;
    }

    @Override
    public String toString() {
        return "CustomerService [customerDAO=" + customerDAO + "]";
    }
        
}

3、Spring-Customer.xml

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">
    
    <bean id="customerService" class="com.mkyong.customer.services.CustomerService">
        <property name="customerDAO" ref="customerDAO" />
    </bean>

    <bean id="customerDAO" class="com.mkyong.customer.dao.CustomerDAO" />

</beans>

二、auto Scanning

1、CustomerDAO.java

package com.mkyong.customer.dao;

import org.springframework.stereotype.Component;

@Component
public class CustomerDAO 
{
    @Override
    public String toString() {
        return "Hello , This is CustomerDAO";
    }	
}

2、CustomerService.java

package com.mkyong.customer.services;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import com.mkyong.customer.dao.CustomerDAO;

@Component
public class CustomerService 
{
    @Autowired
    CustomerDAO customerDAO;

    @Override
    public String toString() {
        return "CustomerService [customerDAO=" + customerDAO + "]";
    }
}

3、Spring-Customer.xml

<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-2.5.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-2.5.xsd">

    <context:component-scan base-package="com.mkyong.customer" />
n
</beans>

三、Annotation Types——自动扫描组件的注释类型

有4种注释类型，分别是：

@Component ——表示一个自动扫描component
@Repository ——表示持久化层的DAO component
@Service ——表示业务逻辑层的Service component
@Controller ——表示表示层的Controller component Spring将会扫描所有用@Component注释过得组件。

　　实际上，@Repository、@Service、@Controller三种注释它们都用@Component注释过。所以，在项目中，我们可以将所有自动扫描组件都用@Component注释，Spring将会扫描所有用@Component注释过得组件。　　但是，为了更好的可读性，应该在不同的应用层中，用不同的注释。

四、Spring Filter Components —— 在自动扫描中过滤组件

1、Filter Component——include

　　用”filter”自动扫描注册组件，这些组件只要匹配定义的”regex”的命名规则，Clasee前就不需要用@Component进行注释。

（1）DAO层，在CustomerDAO.java中

package com.mkyong.customer.dao;

public class CustomerDAO 
{
    @Override
    public String toString() {
        return "Hello , This is CustomerDAO";
    }	
}

（2）Service层，在CustomerService.java中

package com.mkyong.customer.services;

import org.springframework.beans.factory.annotation.Autowired;
import com.mkyong.customer.dao.CustomerDAO;

public class CustomerService 
{
    @Autowired
    CustomerDAO customerDAO;

    @Override
    public String toString() {
        return "CustomerService [customerDAO=" + customerDAO + "]";
    }
        
}

（3）在Spring-Customer.xml中

<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-2.5.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-2.5.xsd">

    <context:component-scan base-package="com.mkyong" >

        <context:include-filter type="regex" 
                       expression="com.mkyong.customer.dao.*DAO.*" />

        <context:include-filter type="regex" 
                       expression="com.mkyong.customer.services.*Service.*" />

    </context:component-scan>

</beans>

　　以上xml文件中，所有文件名字，只要包含DAO和Service（*DAO.*，*Service.*）关键字的，都将被检查注册到Spring容器中。

2、Filter Component——exclude

　　用exclude，制定组件避免被Spring发现并被注册到容器中。
以下配置排除用@Service注释过的组件，注意type=”annotation”

<context:component-scan base-package="com.lei.customer" >
        <context:exclude-filter type="annotation" 
            expression="org.springframework.stereotype.Service" />        
</context:component-scan>

以下配置排除包含”DAO”关键字的组件

<context:component-scan base-package="com.lei" >
    <context:exclude-filter type="regex" expression="com.mkyong.customer.dao.*DAO.*" />        
</context:component-scan>