mercredi 7 mai 2014

Changement de constructeur standard de servlet en Java - Stack Overflow


I have the following code:


public BalleServlet() throws SAXException, IOException, ParserConfigurationException, ServletException {
super();
ServletContext context = getServletContext();
InputSource xmlFile = new InputSource(context.getResourceAsStream("/WEB-INF/balle.xml"));
xd = new XMLDoc(xmlFile);
// TODO Auto-generated constructor stub
}

I used to have just


public BalleServlet() throws SAXException, IOException, ParserConfigurationException, ServletException {
super();
}

and that worked perfectly.


The problem is that getServletContext() seems to be throwing a NullPointerException and I can't completely comprehend why it is doing it. I see many others are strugelling with this as well, but I haven't been able to use the solutions offered. This is the stack trace btw:


java.lang.NullPointerException
at javax.servlet.GenericServlet.getServletContext(GenericServlet.java:125)
at Martin.Berntsen.BalleServlet.<init>(BalleServlet.java:36)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:357)
at java.lang.Class.newInstance(Class.java:310)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:138)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1144)
at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:865)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:136)
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:99)
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:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
at java.lang.Thread.run(Thread.java:695)



This code fixed it:


    public void init(ServletConfig config) throws ServletException {
super.init(config);
ServletContext context = getServletContext();
InputSource xmlFile = new InputSource(context.getResourceAsStream("/WEB-INF/balle.xml"));
try {
xd = new XMLDoc(xmlFile);
} catch (Exception e) {
System.out.println("Something wrong happened");
}
}



This is caused by overriding init(ServletContext context) and not calling super.init(context).



I have the following code:


public BalleServlet() throws SAXException, IOException, ParserConfigurationException, ServletException {
super();
ServletContext context = getServletContext();
InputSource xmlFile = new InputSource(context.getResourceAsStream("/WEB-INF/balle.xml"));
xd = new XMLDoc(xmlFile);
// TODO Auto-generated constructor stub
}

I used to have just


public BalleServlet() throws SAXException, IOException, ParserConfigurationException, ServletException {
super();
}

and that worked perfectly.


The problem is that getServletContext() seems to be throwing a NullPointerException and I can't completely comprehend why it is doing it. I see many others are strugelling with this as well, but I haven't been able to use the solutions offered. This is the stack trace btw:


java.lang.NullPointerException
at javax.servlet.GenericServlet.getServletContext(GenericServlet.java:125)
at Martin.Berntsen.BalleServlet.<init>(BalleServlet.java:36)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:357)
at java.lang.Class.newInstance(Class.java:310)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:138)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1144)
at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:865)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:136)
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:99)
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:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
at java.lang.Thread.run(Thread.java:695)


This code fixed it:


    public void init(ServletConfig config) throws ServletException {
super.init(config);
ServletContext context = getServletContext();
InputSource xmlFile = new InputSource(context.getResourceAsStream("/WEB-INF/balle.xml"));
try {
xd = new XMLDoc(xmlFile);
} catch (Exception e) {
System.out.println("Something wrong happened");
}
}


This is caused by overriding init(ServletContext context) and not calling super.init(context).


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