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+/*
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+ * Licensed to the Apache Software Foundation (ASF) under one or more
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+ * contributor license agreements. See the NOTICE file distributed with
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+ * this work for additional information regarding copyright ownership.
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+ * The ASF licenses this file to You under the Apache License, Version 2.0
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+ * (the "License"); you may not use this file except in compliance with
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+ * the License. You may obtain a copy of the License at
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+ *
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+ * http://www.apache.org/licenses/LICENSE-2.0
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+ *
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+ * Unless required by applicable law or agreed to in writing, software
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+ * distributed under the License is distributed on an "AS IS" BASIS,
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+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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+ * See the License for the specific language governing permissions and
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+ * limitations under the License.
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+ */
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+
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+package org.apache.hadoop.jmx;
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+
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+import java.io.IOException;
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+import java.io.PrintWriter;
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+import java.lang.management.ManagementFactory;
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+import java.lang.reflect.Array;
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+import java.util.Iterator;
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+import java.util.Set;
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+
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+import javax.management.AttributeNotFoundException;
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+import javax.management.InstanceNotFoundException;
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+import javax.management.IntrospectionException;
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+import javax.management.MBeanAttributeInfo;
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+import javax.management.MBeanException;
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+import javax.management.MBeanInfo;
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+import javax.management.MBeanServer;
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+import javax.management.MalformedObjectNameException;
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+import javax.management.ObjectName;
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+import javax.management.ReflectionException;
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+import javax.management.openmbean.CompositeData;
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+import javax.management.openmbean.CompositeType;
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+import javax.management.openmbean.TabularData;
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+import javax.servlet.ServletException;
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+import javax.servlet.http.HttpServlet;
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+import javax.servlet.http.HttpServletRequest;
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+import javax.servlet.http.HttpServletResponse;
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+
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+import org.apache.commons.logging.Log;
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+import org.apache.commons.logging.LogFactory;
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+import org.apache.hadoop.http.HttpServer;
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+import org.codehaus.jackson.JsonFactory;
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+import org.codehaus.jackson.JsonGenerator;
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+
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+/*
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+ * This servlet is based off of the JMXProxyServlet from Tomcat 7.0.14. It has
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+ * been rewritten to be read only and to output in a JSON format so it is not
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+ * really that close to the original.
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+ */
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+/**
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+ * Provides Read only web access to JMX.
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+ * <p>
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+ * This servlet generally will be placed under the /jmx URL for each
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+ * HttpServer. It provides read only
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+ * access to JMX metrics. The optional <code>qry</code> parameter
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+ * may be used to query only a subset of the JMX Beans. This query
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+ * functionality is provided through the
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+ * {@link MBeanServer#queryNames(ObjectName, javax.management.QueryExp)}
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+ * method.
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+ * <p>
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+ * For example <code>http://.../jmx?qry=Hadoop:*</code> will return
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+ * all hadoop metrics exposed through JMX.
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+ * <p>
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+ * If the <code>qry</code> parameter is not formatted correctly then a
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+ * 400 BAD REQUEST http response code will be returned.
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+ * <p>
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+ * The return format is JSON and in the form
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+ * <p>
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+ * <code><pre>
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+ * {
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+ * "beans" : [
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+ * {
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+ * "name":"bean-name"
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+ * ...
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+ * }
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+ * ]
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+ * }
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+ * </pre></code>
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+ * <p>
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+ * The servlet attempts to convert the the JMXBeans into JSON. Each
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+ * bean's attributes will be converted to a JSON object member.
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+ *
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+ * If the attribute is a boolean, a number, a string, or an array
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+ * it will be converted to the JSON equivalent.
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+ *
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+ * If the value is a {@link CompositeData} then it will be converted
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+ * to a JSON object with the keys as the name of the JSON member and
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+ * the value is converted following these same rules.
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+ *
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+ * If the value is a {@link TabularData} then it will be converted
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+ * to an array of the {@link CompositeData} elements that it contains.
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+ *
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+ * All other objects will be converted to a string and output as such.
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+ *
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+ * The bean's name and modelerType will be returned for all beans.
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+ */
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+public class JMXJsonServlet extends HttpServlet {
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+ private static final Log LOG = LogFactory.getLog(JMXJsonServlet.class);
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+
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+ private static final long serialVersionUID = 1L;
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+
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+ // ----------------------------------------------------- Instance Variables
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+ /**
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+ * MBean server.
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+ */
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+ protected transient MBeanServer mBeanServer = null;
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+
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+ // --------------------------------------------------------- Public Methods
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+ /**
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+ * Initialize this servlet.
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+ */
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+ @Override
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+ public void init() throws ServletException {
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+ // Retrieve the MBean server
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+ mBeanServer = ManagementFactory.getPlatformMBeanServer();
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+ }
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+
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+ /**
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+ * Process a GET request for the specified resource.
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+ *
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+ * @param request
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+ * The servlet request we are processing
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+ * @param response
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+ * The servlet response we are creating
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+ */
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+ @Override
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+ public void doGet(HttpServletRequest request, HttpServletResponse response) {
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+ try {
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+ // Do the authorization
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+ if (!HttpServer.hasAdministratorAccess(getServletContext(), request,
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+ response)) {
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+ return;
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+ }
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+
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+ response.setContentType("application/json; charset=utf8");
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+
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+ PrintWriter writer = response.getWriter();
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+
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+ JsonFactory jsonFactory = new JsonFactory();
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+ JsonGenerator jg = jsonFactory.createJsonGenerator(writer);
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+ jg.useDefaultPrettyPrinter();
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+ jg.writeStartObject();
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+ if (mBeanServer == null) {
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+ jg.writeStringField("result", "ERROR");
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+ jg.writeStringField("message", "No MBeanServer could be found");
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+ jg.close();
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+ return;
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+ }
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+ String qry = request.getParameter("qry");
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+ if (qry == null) {
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+ qry = "*:*";
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+ }
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+ listBeans(jg, new ObjectName(qry));
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+ jg.close();
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+ } catch (IOException e) {
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+ LOG.error("Caught an exception while processing JMX request", e);
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+ response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
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+ } catch (MalformedObjectNameException e) {
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+ LOG.error("Caught an exception while processing JMX request", e);
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+ response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
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+ }
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+ }
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+
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+ // --------------------------------------------------------- Private Methods
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+ private void listBeans(JsonGenerator jg, ObjectName qry) throws IOException {
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+ LOG.debug("Listing beans for "+qry);
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+ Set<ObjectName> names = null;
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+ names = mBeanServer.queryNames(qry, null);
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+
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+ jg.writeArrayFieldStart("beans");
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+ Iterator<ObjectName> it = names.iterator();
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+ while (it.hasNext()) {
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+ ObjectName oname = it.next();
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+ MBeanInfo minfo;
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+ String code;
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+ try {
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+ minfo = mBeanServer.getMBeanInfo(oname);
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+ code = minfo.getClassName();
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+ try {
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+ if ("org.apache.commons.modeler.BaseModelMBean".equals(code)) {
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+ code = (String) mBeanServer.getAttribute(oname, "modelerType");
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+ }
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+ } catch (AttributeNotFoundException e) {
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+ //Ignored the modelerType attribute was not found, so use the class name instead.
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+ } catch (MBeanException e) {
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+ //The code inside the attribute getter threw an exception so log it, and
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+ // fall back on the class name
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+ LOG.error("getting attribute modelerType of "+oname+" threw an exception", e);
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+ } catch (RuntimeException e) {
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+ //For some reason even with an MBeanException available to them Runtime exceptions
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+ //can still find their way through, so treat them the same as MBeanException
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+ LOG.error("getting attribute modelerType of "+oname+" threw an exception", e);
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+ } catch (ReflectionException e) {
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+ //This happens when the code inside the JMX bean (setter?? from the java docs)
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+ //threw an exception, so log it and fall back on the class name
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+ LOG.error("getting attribute modelerType of "+oname+" threw an exception", e);
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+ }
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+ } catch (InstanceNotFoundException e) {
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+ //Ignored for some reason the bean was not found so don't output it
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+ continue;
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+ } catch (IntrospectionException e) {
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+ //This is an internal error, something odd happened with reflection so log it and
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+ //don't output the bean.
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+ LOG.error("Problem while trying to process JMX query: "+qry+" with MBean "+oname, e);
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+ continue;
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+ } catch (ReflectionException e) {
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+ //This happens when the code inside the JMX bean threw an exception, so log it and
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+ //don't output the bean.
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+ LOG.error("Problem while trying to process JMX query: "+qry+" with MBean "+oname, e);
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+ continue;
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+ }
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+
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+ jg.writeStartObject();
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+ jg.writeStringField("name", oname.toString());
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+ // can't be null - I think
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+
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+ jg.writeStringField("modelerType", code);
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+
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+ MBeanAttributeInfo attrs[] = minfo.getAttributes();
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+ for (int i = 0; i < attrs.length; i++) {
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+ writeAttribute(jg, oname, attrs[i]);
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+ }
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+ // LOG.error("Caught Error writing value ",t);
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+ // ExceptionUtils.handleThrowable(t);
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+ //}
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+ jg.writeEndObject();
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+ }
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+ jg.writeEndArray();
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+ }
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+
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+ private void writeAttribute(JsonGenerator jg, ObjectName oname, MBeanAttributeInfo attr) throws IOException {
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+ if (!attr.isReadable()) {
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+ return;
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+ }
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+ String attName = attr.getName();
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+ if ("modelerType".equals(attName)) {
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+ return;
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+ }
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+ if (attName.indexOf("=") >= 0 || attName.indexOf(":") >= 0
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+ || attName.indexOf(" ") >= 0) {
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+ return;
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+ }
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+ Object value = null;
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+ try {
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+ value = mBeanServer.getAttribute(oname, attName);
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+ } catch (AttributeNotFoundException e) {
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+ //Ignored the attribute was not found, which should never happen because the bean
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+ //just told us that it has this attribute, but if this happens just don't output
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+ //the attribute.
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+ return;
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+ } catch (MBeanException e) {
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+ //The code inside the attribute getter threw an exception so log it, and
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+ // skip outputting the attribute
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+ LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
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+ return;
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+ } catch (RuntimeException e) {
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+ //For some reason even with an MBeanException available to them Runtime exceptions
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+ //can still find their way through, so treat them the same as MBeanException
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+ LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
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+ return;
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+ } catch (ReflectionException e) {
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+ //This happens when the code inside the JMX bean (setter?? from the java docs)
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+ //threw an exception, so log it and skip outputting the attribute
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+ LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
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+ return;
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+ } catch (InstanceNotFoundException e) {
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+ //Ignored the mbean itself was not found, which should never happen because we
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+ //just accessed it (perhaps something unregistered in-between) but if this
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+ //happens just don't output the attribute.
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+ return;
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+ }
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+
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+ writeAttribute(jg, attName, value);
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+ }
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+
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+ private void writeAttribute(JsonGenerator jg, String attName, Object value) throws IOException {
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+ jg.writeFieldName(attName);
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+ writeObject(jg, value);
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+ }
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+
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+ private void writeObject(JsonGenerator jg, Object value) throws IOException {
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+ if(value == null) {
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+ jg.writeNull();
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+ } else {
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+ Class<?> c = value.getClass();
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+ if (c.isArray()) {
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+ jg.writeStartArray();
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+ int len = Array.getLength(value);
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+ for (int j = 0; j < len; j++) {
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+ Object item = Array.get(value, j);
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+ writeObject(jg, item);
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+ }
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+ jg.writeEndArray();
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+ } else if(value instanceof Number) {
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+ Number n = (Number)value;
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+ jg.writeNumber(n.toString());
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+ } else if(value instanceof Boolean) {
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+ Boolean b = (Boolean)value;
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+ jg.writeBoolean(b);
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+ } else if(value instanceof CompositeData) {
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+ CompositeData cds = (CompositeData)value;
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+ CompositeType comp = cds.getCompositeType();
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+ Set<String> keys = comp.keySet();
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+ jg.writeStartObject();
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+ for(String key: keys) {
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+ writeAttribute(jg, key, cds.get(key));
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+ }
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+ jg.writeEndObject();
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+ } else if(value instanceof TabularData) {
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+ TabularData tds = (TabularData)value;
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+ jg.writeStartArray();
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+ for(Object entry : tds.values()) {
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+ writeObject(jg, entry);
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+ }
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+ jg.writeEndArray();
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+ } else {
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+ jg.writeString(value.toString());
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+ }
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+ }
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+ }
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+}
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Owen O'Malley