Question

我打算在Spring DI中使用logger（带有slf4j的log4J）。

我正在尝试使用DI初始化主记录器类并在测试类中自动装配该实例。但是那个实例总是无效的。我不确定我做错了什么。请注意其在IBM WAS 6.1上部署的Web应用程序。

这就是我正在做的事情

所有课程都在 com.test 包中。

@Repository
           public class TestLogger
            {

            @Autowired
            MainLogger error; // this instance of Mainlogger is always null         

    //if **MainLogger error = new MainLogger();**  is used this is working fine!!
           public void test(){

             error.logerror("test"); //null pointer here

             }
           }

MainLogger Class

public class MainLogger {


    public static void main(String[] args) {
         Logger logger = LoggerFactory.getLogger(MainLogger.class);
         String str = "Logger check check";
        logger.info(str); 

    }
        public void loginfo(String para)
        {
             Logger logger = LoggerFactory.getLogger(VpayCoreLogger.class);
             logger.info(para);
        }

        public void logdebug(String para)
        {
            Logger logger = LoggerFactory.getLogger(VpayCoreLogger.class);
            logger.debug(para);
        }

        public void logerror(String para)
        {
            Logger logger = LoggerFactory.getLogger(VpayCoreLogger.class);

            logger.error(para);
        }

    }

}

应用程序上下文XML

<?xml version="1.0" encoding="UTF-8"?>
<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"
    xmlns:mvc="http://www.springframework.org/schema/mvc" 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/context http://www.springframework.org/schema/context/spring-context-3.1.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.1.xsd
        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd">

<bean id="error" class="com.test.MainLogger">
</bean>


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

</beans>

WEB XML

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" 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">
    <display-name>testApp</display-name>
    <welcome-file-list>
        <welcome-file>testDAO.jsp</welcome-file>

    </welcome-file-list>
    <context-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/applicationContext.xml</param-value>
    </context-param>

    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener
        </listener-class>
    </listener>
</web-app>

Answer 1

使用TestLogger注释@Component以使其成为bean。否则它将不会被组件扫描拾取，使其不符合自动装配/ DI的条件。

   @Component
   public class TestLogger
   {
      //code goes here
   }

Answer 2

不确定它的答案是否正确，但我还是以某种方式工作了。问题在于使用setter或Constructor自动化字段。

@Repository
public class TestLogger
{

private static MainLogger error;     
@Autowired
public TestLogger(MainLogger error)
{
 this.error=error;
}

public TestLogger()
{

}
 public void test(){

       error.logerror("test");     
       }
    }

注入Logger对象时使用空指针在Spring 3.1.0中使用DI

2 个答案: