来自 Tomcat 的 Servlet 调用抛出 HTTP 状态 500 - java.lang.NullPointerException
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时间：2020-08-13 11:22:49 来源:igfitidea点击:
Servlet call from Tomcat throwing HTTP Status 500 - java.lang.NullPointerException
提问by BollyBoy
I am trying to call my servlet GetAttributeValueServletfrom apache tomcatand this error has been shown.
The Servlet is in CloudWebServerClient.
我正在尝试从中调用我的 servlet GetAttributeValueServlet，apache tomcat并且已显示此错误。Servlet 在CloudWebServerClient.
Severe: Servlet.service() for servlet [servlet.GetAttributeValueServlet] in context with path [/CloudWebServiceClient] threw exception
AxisFault
faultCode: {http://schemas.xmlsoap.org/soap/envelope/}Server.userException
faultSubcode:
faultString: java.lang.NullPointerException
faultActor:
faultNode:
faultDetail:
{http://xml.apache.org/axis/}hostname
java.lang.NullPointerException
at org.apache.axis.message.SOAPFaultBuilder.createFault(SOAPFaultBuilder.java:222)
at org.apache.axis.message.SOAPFaultBuilder.endElement(SOAPFaultBuilder.java:129)
at org.apache.axis.encoding.DeserializationContext.endElement(DeserializationContext.java:1087)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl.parse(Unknown Source)
at org.apache.axis.encoding.DeserializationContext.parse(DeserializationContext.java:227)
at org.apache.axis.SOAPPart.getAsSOAPEnvelope(SOAPPart.java:696)
at org.apache.axis.Message.getSOAPEnvelope(Message.java:435)
at org.apache.axis.transport.http.HTTPSender.readFromSocket(HTTPSender.java:796)
at org.apache.axis.transport.http.HTTPSender.invoke(HTTPSender.java:144)
at org.apache.axis.strategies.InvocationStrategy.visit(InvocationStrategy.java:32)
at org.apache.axis.SimpleChain.doVisiting(SimpleChain.java:118)
at org.apache.axis.SimpleChain.invoke(SimpleChain.java:83)
at org.apache.axis.client.AxisClient.invoke(AxisClient.java:165)
at org.apache.axis.client.Call.invokeEngine(Call.java:2784)
at org.apache.axis.client.Call.invoke(Call.java:2767)
at org.apache.axis.client.Call.invoke(Call.java:2443)
at org.apache.axis.client.Call.invoke(Call.java:2366)
at org.apache.axis.client.Call.invoke(Call.java:1812)
at com.client.service.WebServiceProxySoapBindingStub.getAttributeValue(WebServiceProxySoapBindingStub.java:297)
at com.client.service.WebServiceProxyProxy.getAttributeValue(WebServiceProxyProxy.java:50)
at servlet.GetAttributeValueServlet.doGet(GetAttributeValueServlet.java:48)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:409)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1044)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Web.xml:
网页.xml：
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 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>CloudWebServiceServer</display-name>
<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>
<servlet>
<display-name>GetAttributeValueServlet</display-name>
<servlet-name>GetAttributeValueServlet</servlet-name>
<servlet-class>com.src.servlet.GetAttributeValueServlet</servlet-class>
</servlet>
<servlet>
<display-name>Apache-Axis Servlet</display-name>
<servlet-name>AxisServlet</servlet-name>
<servlet-class>org.apache.axis.transport.http.AxisServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>GetAttributeValueServlet</servlet-name>
<url-pattern>/CloudWebServiceClient/WebContent/GetAttributeValueServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>AxisServlet</servlet-name>
<url-pattern>/servlet/AxisServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>AxisServlet</servlet-name>
<url-pattern>*.jws</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>AxisServlet</servlet-name>
<url-pattern>/services/*</url-pattern>
</servlet-mapping>
<servlet>
<display-name>Axis Admin Servlet</display-name>
<servlet-name>AdminServlet</servlet-name>
<servlet-class>org.apache.axis.transport.http.AdminServlet</servlet-class>
<load-on-startup>100</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>AdminServlet</servlet-name>
<url-pattern>/servlet/AdminServlet</url-pattern>
</servlet-mapping>
</web-app>
GetAttributeValueServlet:
获取属性值Servlet：
package servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.client.service.WebServiceProxy;
import com.client.service.WebServiceProxyProxy;
/**
* Servlet implementation class GetAttributeValueServlet
*/
@WebServlet("/GetAttributeValueServlet")
public class GetAttributeValueServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public GetAttributeValueServlet() {
super();
// TODO Auto-generated constructor stub
}
/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
response.setHeader("Access-Control-Allow-Origin", "*");
response.setContentType("text/xml;charset=utf-8");
String EntityID=request.getParameter("entity_id");
String AttrName=request.getParameter("attrName");
//String Value=request.getParameter("value");
System.out.println(EntityID+AttrName);
WebServiceProxy wsp = new WebServiceProxyProxy();
System.out.println("Huuu"); //just to see if it is coming to this point and yes it comes to this point and after that throws exception!
String isGet = wsp.getAttributeValue(EntityID, AttrName);
System.out.println("Hagfgfg"); //it doesn't shows this value!
PrintWriter pw = response.getWriter();
pw.print(isGet);
return;
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
}
}
}
采纳答案by BollyBoy
I resolved it.... The problem was in parameter attrName which was Null and it was because of wrong function call ;) thanx anyways
我解决了它.... 问题出在参数 attrName 中，该参数为 Null，这是因为函数调用错误；) 无论如何，thanx
回答by developerwjk
Before using values you pull from request.getParameter() you should check them to see if they are null and do something if they are.
在使用从 request.getParameter() 中提取的值之前，您应该检查它们是否为空，如果是，则执行一些操作。
String entityID = request.getParameter("entity_id");
if(entityID==null)
{
entityID = "";
//or maybe print a message to user "Entity ID is required field" and return;
}
Or you can make sure they're not null like this:
或者你可以确保它们不是这样的：
String entityID = "" + request.getParameter("entity_id");
This would mean if what comes out of request.getParameter() was null, now it will be the String value "null" rather than null.
这意味着如果 request.getParameter() 的结果为空，现在它将是字符串值“空”而不是空。
