java - JAX-WS Web 服务内部的 EJB 对象空指针异常

Question

我尝试开发一个 Web 服务应用程序，该应用程序在 Web 服务类中使用 EJB 函数，但 EJB 对象在运行时为空。

我正在使用 Spring 应用程序上下文配置 Web 服务。是不是有什么问题呢？

代码:

public class CreditCardService implements ICreditCardService {  

  private static final Logger logger = Logger.getLogger(CreditCardService.class.getName());  

  @EJB  
  private CreditcardFacadeLocal databaseFacade;  

  @Override  
  public void addCreditCard(Creditcard card) {  
    logger.log(Level.INFO, "Add credit card start");  
    databaseFacade.addCreditCard(card); // NPE Here  
    logger.log(Level.INFO, "Add create card finish");  
  }  
} 

Web.xml

<?xml version="1.0" encoding="UTF-8"?>  
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">  

    <display-name>CreditCardWebService</display-name>  
    <context-param>  
        <param-name>contextConfigLocation</param-name>  
        <param-value>WEB-INF/beans.xml</param-value>  
    </context-param>  
    <listener>  
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>  
    </listener>  

    <servlet>  
        <description>Apache CXF Endpoint</description>  
        <display-name>cxf</display-name>  
        <servlet-name>cxf</servlet-name>  
        <servlet-class>org.apache.cxf.transport.servlet.CXFServlet</servlet-class>  
        <load-on-startup>1</load-on-startup>  
        <enabled>true</enabled>  
        <async-supported>false</async-supported>  
    </servlet>  
    <servlet-mapping>  
        <servlet-name>cxf</servlet-name>  
        <url-pattern>  
        /services/*</url-pattern>  
    </servlet-mapping>  
    <session-config>  
        <session-timeout>60</session-timeout>  
    </session-config>  
    <welcome-file-list>  
        <welcome-file>index.html</welcome-file>  
        <welcome-file>index.htm</welcome-file>  
        <welcome-file>index.jsp</welcome-file>  
        <welcome-file>default.html</welcome-file>  
        <welcome-file>default.htm</welcome-file>  
        <welcome-file>default.jsp</welcome-file>  
    </welcome-file-list>  
</web-app> 

Beans.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:jaxws="http://cxf.apache.org/jaxws"  
    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://cxf.apache.org/jaxws http://cxf.apache.org/schemas/jaxws.xsd">  
    <import resource="classpath:META-INF/cxf/cxf.xml" />  
    <!--  <import resource="classpath:META-INF/cxf/cxf-extension-soap.xml" /> -->  
    <import resource="classpath:META-INF/cxf/cxf-servlet.xml" />  

    <!-- Create Web Service End Point using Spring DI-->  
    <jaxws:endpoint xmlns:tns="http://service.peter.com/"  
        id="creditcardservice" implementor="com.peter.service.CreditCardService"  
        wsdlLocation="wsdl/creditcardservice.wsdl" endpointName="tns:CreditCardServicePort"  
        serviceName="tns:CreditCardServiceService" address="/CreditCardServicePort">  
        <jaxws:features>  
            <bean class="org.apache.cxf.feature.LoggingFeature" />  
        </jaxws:features>  
    </jaxws:endpoint>  
</beans> 

ejb 对象为空的原因是什么？它是否与CreditCardService类的Spring DI相关，但没有实例化ejb对象？

CXF servlet 的用途是什么？它是用来处理Web服务请求的吗？

请帮忙。

谢谢。

Answer 1

CXF servlet 用于处理 Web 服务请求。 CXF 是一个 Web 服务堆栈，它基于 JAX-WS，但具有一些 JAX-WS 所没有的功能。看看here 。

您无法在 Web 服务中使用 @EJB 注释注入(inject) EJB 对象。 @EJB 注释仅适用于托管 bean，例如 servlet 等...或者在 EJB 上下文中。

要注入(inject) EJB，您需要在 Web 服务中查找 JNDI。所以它会是这样的:

/**
 * Java global JNDI.
 */
private static final String JAVA_GLOBAL = "java:global/";

/**
 * Application name in application server.
 */
private static final String APP_NAME = "YourAppName/";

/**
 * Application EJB jar name.
 */
private static final String APP_EJB = "your-ejb/";

/**
 * Credit EJB constant.
 */
public static final String CREDIT_EJB = JAVA_GLOBAL + APP_NAME + APP_EJB + "CreditcardFacade!your.package.CreditcardFacadeLocal";

现在创建一个通用方法来从 JNDI 获取 EJB 对象:

/**
 * Gets local EJB from JNDI.
 *
 * @param jndiName JNDI constant name to look up for EJB
 * @param <T> generic object
 * @return local EJB object loaded from JNDI
 */
public static <T> T getLocalEJB(String jndiName) {
    try {
        InitialContext context = new InitialContext();
        return (T) context.lookup(jndiName);
    } catch (NamingException e) {
        LOGGER.error("Naming exception occurred while trying to load EJB from JNDI with JNDI name: " + jndiName, e);
        throw new RuntimeException("Naming exception occurred while trying to load EJB from JNDI with JNDI name: " + jndiName, e);
    }
}

现在您可以像这样获取 EJB:

CreditcardFacadeLocal facade = JndiUtils.getLocalEJB(JndiUtils.CREDIT_EJB);

我自己在 CXF Web 服务中完成了此操作，一切正常。