如何在Validator类中@Autowire对象？

Question

是否可以在Validation类中自动装配对象？对于应该是Autowired的对象,我一直都为null ...

Answer 1

你的Validation类是一个启用的Spring bean ??? 如果没有,您将始终为自动装配的对象获取null.确保已启用验证类.

并且不要忘记启用Annotation配置bean后处理器(参见<context:annotation-config />元素)

<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:annotation-config />
</beans>

如何将Validation类作为托管Spring bean启用.或

1°使用xml(如上图所示)

<beans ...>
    <bean class="AccessRequestValidator"/>
    <context:annotation-config />
</beans>

2°通过使用注释(注意@Component就在类之上)

@Component
public class AccessRequestValidator implements Validator {

}

但是要启用Spring注释组件扫描,必须启用bean-post处理器(注意<context:component-scan element)

<beans ...>
    <context:annotation-config />
    <context:component-scan base-package="<PUT_RIGHT_HERE_WHICH_ROOT_PACKAGE_SHOULD_SPRING_LOOK_FOR_ANY_ANNOTATED_BEAN>"/>
</beans>

在您的控制器内部,只需这样做(不要使用新的运算符)

选择以下策略之一

public class MyController implements Controller {

    /**
      * You can use FIELD @Autowired
      */
    @Autowired
    private AccessRequestValidator accessRequestValidator;

    /**
      * You can use PROPERTY @Autowired
      */
    private AccessRequestValidator accessRequestValidator;
    private @Autowired void setAccessRequestValidator(AccessRequestValidator accessRequestValidator) {
        this.accessRequestValidator = accessRequestValidator;
    }

    /**
      * You can use CONSTRUCTOR @Autowired
      */
    private AccessRequestValidator accessRequestValidator;

    @Autowired
    public MyController(AccessRequestValidator accessRequestValidator) {
        this.accessRequestValidator = accessRequestValidator;
    }   

}

UPDATE

您的Web应用程序结构应如下所示

<CONTEXT-NAME>/
       WEB-INF/
           web.xml
           <SPRING-SERVLET-NAME>-servlet.xml
           business-context.xml
           classes/
               /com
                   /wuntee
                       /taac
                           /validator
                               AccessRequestValidator.class
           lib/
               /**
                 * libraries needed by your project goes here
                 */

您的web.xml应该是(NOTICE contextConfigLocation context-param和ContextLoaderListener)

<web-app version="2.4" 
    xmlns="http://java.sun.com/xml/ns/j2ee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
                       http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <!--If your business-context.xml lives in the root of classpath-->
        <!--replace by classpath:business-context.xml-->
        <param-value>
            /WEB-INF/business-context.xml
        </param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
    <servlet>
        <servlet-name><SPRING-SERVLET-NAME></servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name><SPRING-SERVLET-NAME></servlet-name>
        <url-pattern>*.htm</url-pattern>
    </servlet-mapping>
</web-app>

你的<SPRING-SERVLET-NAME> -servlet.xml应该是这样的(注意我使用的是Spring 2.5 - 如果你使用3.0则替换)

 <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">
    <!--ANY HANDLER MAPPING-->
    <!--ANY VIEW RESOLVER-->
    <context:component-scan base-package="com.wuntee.taac"/>
    <context:annotation-config/>
</beans>