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ThreadDumpServlet.java
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/
ThreadDumpServlet.java
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package com.codahale.metrics.servlets;
import com.codahale.metrics.jvm.ThreadDump;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.management.ManagementFactory;
/**
* An HTTP servlets which outputs a {@code text/plain} dump of all threads in
* the VM. Only responds to {@code GET} requests.
*/
public class ThreadDumpServlet extends HttpServlet {
private static final long serialVersionUID = -2690343532336103046L;
private static final String CONTENT_TYPE = "text/plain";
private transient ThreadDump threadDump;
@Override
public void init() throws ServletException {
try {
// Some PaaS like Google App Engine blacklist java.lang.managament
this.threadDump = new ThreadDump(ManagementFactory.getThreadMXBean());
} catch (NoClassDefFoundError ncdfe) {
this.threadDump = null; // we won't be able to provide thread dump
}
}
@Override
protected void doGet(HttpServletRequest req,
HttpServletResponse resp) throws ServletException, IOException {
final boolean includeMonitors = getParam(req.getParameter("monitors"), true);
final boolean includeSynchronizers = getParam(req.getParameter("synchronizers"), true);
resp.setStatus(HttpServletResponse.SC_OK);
resp.setContentType(CONTENT_TYPE);
resp.setHeader("Cache-Control", "must-revalidate,no-cache,no-store");
if (threadDump == null) {
resp.getWriter().println("Sorry your runtime environment does not allow to dump threads.");
return;
}
try (OutputStream output = resp.getOutputStream()) {
threadDump.dump(includeMonitors, includeSynchronizers, output);
}
}
private static Boolean getParam(String initParam, boolean defaultValue) {
return initParam == null ? defaultValue : Boolean.parseBoolean(initParam);
}
}