I implemented an UncaughtExceptionHandler on StartUp of tomcat:
Thread.setDefaultUncaughtExceptionHandler(new UncaughtExceptionHandler() {
@Override
public void uncaughtException(Thread t, Throwable e) {
LOGGER.error("Uncaught Exception");
}
});
When I produce an Exception in a Servlet it is not caught by my Handler:
protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
int i = 1/0;
The console says:
Feb 13, 2014 8:23:58 AM org.apache.catalina.core.StandardWrapperValve invoke Schwerwiegend: Servlet.service() for servlet [ConnectGatewaysServlet] in context with path [/infraview] threw exception java.lang.ArithmeticException: / by zero at net.test.gateway.ConnectGatewaysServlet.doPost(ConnectGatewaysServlet.java:73) at javax.servlet.http.HttpServlet.service(HttpServlet.java:647) at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
How do I implement an UncaughtExceptionHandler for Servlets?
That's normal. Tomcat has more than a hundred threads, and the uncaught exception handlers are associated to a given thread (it's coming from the time of ThreadGroups
).
What you can do is to wrap the contents of the doPost()
in a try-catch
block.
The other way is to define error handling in the web.xml
- you can also create a servlet for handling errors in other servlets :-) See an example here .
I found the below example in a website, thought this refers to exactly your question http://www.journaldev.com/1973/servlet-exception-and-error-handling-example-tutorial
Java Code:
package com.journaldev.servlet.exception;
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;
@WebServlet("/AppExceptionHandler")
public class AppExceptionHandler extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
processError(request, response);
}
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
processError(request, response);
}
private void processError(HttpServletRequest request,
HttpServletResponse response) throws IOException {
// Analyze the servlet exception
Throwable throwable = (Throwable) request
.getAttribute("javax.servlet.error.exception");
Integer statusCode = (Integer) request
.getAttribute("javax.servlet.error.status_code");
String servletName = (String) request
.getAttribute("javax.servlet.error.servlet_name");
if (servletName == null) {
servletName = "Unknown";
}
String requestUri = (String) request
.getAttribute("javax.servlet.error.request_uri");
if (requestUri == null) {
requestUri = "Unknown";
}
// Set response content type
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.write("<html><head><title>Exception/Error Details</title></head><body>");
if(statusCode != 500){
out.write("<h3>Error Details</h3>");
out.write("<strong>Status Code</strong>:"+statusCode+"<br>");
out.write("<strong>Requested URI</strong>:"+requestUri);
}else{
out.write("<h3>Exception Details</h3>");
out.write("<ul><li>Servlet Name:"+servletName+"</li>");
out.write("<li>Exception Name:"+throwable.getClass().getName()+"</li>");
out.write("<li>Requested URI:"+requestUri+"</li>");
out.write("<li>Exception Message:"+throwable.getMessage()+"</li>");
out.write("</ul>");
}
out.write("<br><br>");
out.write("<a href=\"index.html\">Home Page</a>");
out.write("</body></html>");
}
}
WEB.XML ERROR HANDLING:
<?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" 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>ServletExceptionHandling</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
</welcome-file-list>
<error-page>
<error-code>404</error-code>
<location>/AppExceptionHandler</location>
</error-page>
<error-page>
<exception-type>javax.servlet.ServletException</exception-type>
<location>/AppExceptionHandler</location>
</error-page>
</web-app>
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