hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/jmx/JMXJsonServlet.java - hadoop - Git at Google

 /*
  * Licensed to the Apache Software Foundation (ASF) under one or more
  * contributor license agreements.  See the NOTICE file distributed with
  * this work for additional information regarding copyright ownership.
  * The ASF licenses this file to You under the Apache License, Version 2.0
  * (the "License"); you may not use this file except in compliance with
  * the License.  You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package org.apache.hadoop.jmx;

 import org.apache.hadoop.http.HttpServer2;
 import org.codehaus.jackson.JsonFactory;
 import org.codehaus.jackson.JsonGenerator;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;

 import javax.management.AttributeNotFoundException;
 import javax.management.InstanceNotFoundException;
 import javax.management.IntrospectionException;
 import javax.management.MBeanAttributeInfo;
 import javax.management.MBeanException;
 import javax.management.MBeanInfo;
 import javax.management.MBeanServer;
 import javax.management.MalformedObjectNameException;
 import javax.management.ObjectName;
 import javax.management.ReflectionException;
 import javax.management.RuntimeErrorException;
 import javax.management.RuntimeMBeanException;
 import javax.management.openmbean.CompositeData;
 import javax.management.openmbean.CompositeType;
 import javax.management.openmbean.TabularData;
 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.PrintWriter;
 import java.lang.management.ManagementFactory;
 import java.lang.reflect.Array;
 import java.util.Iterator;
 import java.util.Set;

 /*
  * This servlet is based off of the JMXProxyServlet from Tomcat 7.0.14. It has
  * been rewritten to be read only and to output in a JSON format so it is not
  * really that close to the original.
  */
 /**
  * Provides Read only web access to JMX.
  * <p>
  * This servlet generally will be placed under the /jmx URL for each
  * HttpServer.  It provides read only
  * access to JMX metrics.  The optional <code>qry</code> parameter
  * may be used to query only a subset of the JMX Beans.  This query
  * functionality is provided through the
  * {@link MBeanServer#queryNames(ObjectName, javax.management.QueryExp)}
  * method.
  * <p>
  * For example <code>http://.../jmx?qry=Hadoop:*</code> will return
  * all hadoop metrics exposed through JMX.
  * <p>
  * The optional <code>get</code> parameter is used to query an specific
  * attribute of a JMX bean.  The format of the URL is
  * <code>http://.../jmx?get=MXBeanName::AttributeName<code>
  * <p>
  * For example
  * <code>
  * http://../jmx?get=Hadoop:service=NameNode,name=NameNodeInfo::ClusterId
  * </code> will return the cluster id of the namenode mxbean.
  * <p>
  * If the <code>qry</code> or the <code>get</code> parameter is not formatted
  * correctly then a 400 BAD REQUEST http response code will be returned.
  * <p>
  * If a resouce such as a mbean or attribute can not be found,
  * a 404 SC_NOT_FOUND http response code will be returned.
  * <p>
  * The return format is JSON and in the form
  * <p>
  *  <code><pre>
  *  {
  *    "beans" : [
  *      {
  *        "name":"bean-name"
  *        ...
  *      }
  *    ]
  *  }
  *  </pre></code>
  *  <p>
  *  The servlet attempts to convert the the JMXBeans into JSON. Each
  *  bean's attributes will be converted to a JSON object member.
  *
  *  If the attribute is a boolean, a number, a string, or an array
  *  it will be converted to the JSON equivalent.
  *
  *  If the value is a {@link CompositeData} then it will be converted
  *  to a JSON object with the keys as the name of the JSON member and
  *  the value is converted following these same rules.
  *
  *  If the value is a {@link TabularData} then it will be converted
  *  to an array of the {@link CompositeData} elements that it contains.
  *
  *  All other objects will be converted to a string and output as such.
  *
  *  The bean's name and modelerType will be returned for all beans.
  *
  */
 public class JMXJsonServlet extends HttpServlet {
   private static final Logger LOG =
       LoggerFactory.getLogger(JMXJsonServlet.class);
   static final String ACCESS_CONTROL_ALLOW_METHODS =
       "Access-Control-Allow-Methods";
   static final String ACCESS_CONTROL_ALLOW_ORIGIN =
       "Access-Control-Allow-Origin";

   private static final long serialVersionUID = 1L;

   /**
    * MBean server.
    */
   protected transient MBeanServer mBeanServer = null;

   // --------------------------------------------------------- Public Methods
   /**
    * Initialize this servlet.
    */
   @Override
   public void init() throws ServletException {
     // Retrieve the MBean server
     mBeanServer = ManagementFactory.getPlatformMBeanServer();
   }

   protected boolean isInstrumentationAccessAllowed(HttpServletRequest request,
       HttpServletResponse response) throws IOException {
     return HttpServer2.isInstrumentationAccessAllowed(getServletContext(),
         request, response);
   }

   /**
    * Disable TRACE method to avoid TRACE vulnerability.
    */
   @Override
   protected void doTrace(HttpServletRequest req, HttpServletResponse resp)
       throws ServletException, IOException {
     resp.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED);
   }

   /**
    * Process a GET request for the specified resource.
    *
    * @param request
    *          The servlet request we are processing
    * @param response
    *          The servlet response we are creating
    */
   @Override
   public void doGet(HttpServletRequest request, HttpServletResponse response) {
     String jsonpcb = null;
     PrintWriter writer = null;
     try {
       if (!isInstrumentationAccessAllowed(request, response)) {
         return;
       }

       JsonGenerator jg = null;
       try {
         writer = response.getWriter();

         response.setContentType("application/json; charset=utf8");
         response.setHeader(ACCESS_CONTROL_ALLOW_METHODS, "GET");
         response.setHeader(ACCESS_CONTROL_ALLOW_ORIGIN, "*");

       JsonFactory jsonFactory = new JsonFactory();
       jg = jsonFactory.createJsonGenerator(writer);
       jg.disable(JsonGenerator.Feature.AUTO_CLOSE_TARGET);
       jg.useDefaultPrettyPrinter();
       jg.writeStartObject();

       if (mBeanServer == null) {
         jg.writeStringField("result", "ERROR");
         jg.writeStringField("message", "No MBeanServer could be found");
         jg.close();
         LOG.error("No MBeanServer could be found.");
         response.setStatus(HttpServletResponse.SC_NOT_FOUND);
         return;
       }

       // query per mbean attribute
       String getmethod = request.getParameter("get");
       if (getmethod != null) {
         String[] splitStrings = getmethod.split("\\:\\:");
         if (splitStrings.length != 2) {
           jg.writeStringField("result", "ERROR");
           jg.writeStringField("message", "query format is not as expected.");
           jg.close();
           response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
           return;
         }
         listBeans(jg, new ObjectName(splitStrings[0]), splitStrings[1],
             response);
         jg.close();
         return;

       }

         // query per mbean
         String qry = request.getParameter("qry");
         if (qry == null) {
           qry = "*:*";
         }
         listBeans(jg, new ObjectName(qry), null, response);
       } finally {
         if (jg != null) {
           jg.close();
         }
         if (writer != null) {
           writer.close();
         }
       }
     } catch ( IOException e ) {
       LOG.error("Caught an exception while processing JMX request", e);
       response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
     } catch ( MalformedObjectNameException e ) {
       LOG.error("Caught an exception while processing JMX request", e);
       response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
     } finally {
       if (writer != null) {
         writer.close();
       }
     }
   }

   // --------------------------------------------------------- Private Methods
   private void listBeans(JsonGenerator jg, ObjectName qry, String attribute,
       HttpServletResponse response)
   throws IOException {
     LOG.debug("Listing beans for "+qry);
     Set<ObjectName> names = null;
     names = mBeanServer.queryNames(qry, null);

     jg.writeArrayFieldStart("beans");
     Iterator<ObjectName> it = names.iterator();
     while (it.hasNext()) {
       ObjectName oname = it.next();
       MBeanInfo minfo;
       String code = "";
       Object attributeinfo = null;
       try {
         minfo = mBeanServer.getMBeanInfo(oname);
         code = minfo.getClassName();
         String prs = "";
         try {
           if ("org.apache.commons.modeler.BaseModelMBean".equals(code)) {
             prs = "modelerType";
             code = (String) mBeanServer.getAttribute(oname, prs);
           }
           if (attribute!=null) {
             prs = attribute;
             attributeinfo = mBeanServer.getAttribute(oname, prs);
           }
         } catch (AttributeNotFoundException e) {
           // If the modelerType attribute was not found, the class name is used
           // instead.
           LOG.error("getting attribute " + prs + " of " + oname
               + " threw an exception", e);
         } catch (MBeanException e) {
           // The code inside the attribute getter threw an exception so log it,
           // and fall back on the class name
           LOG.error("getting attribute " + prs + " of " + oname
               + " threw an exception", e);
         } catch (RuntimeException e) {
           // For some reason even with an MBeanException available to them
           // Runtime exceptionscan still find their way through, so treat them
           // the same as MBeanException
           LOG.error("getting attribute " + prs + " of " + oname
               + " threw an exception", e);
         } catch ( ReflectionException e ) {
           // This happens when the code inside the JMX bean (setter?? from the
           // java docs) threw an exception, so log it and fall back on the
           // class name
           LOG.error("getting attribute " + prs + " of " + oname
               + " threw an exception", e);
         }
       } catch (InstanceNotFoundException e) {
         //Ignored for some reason the bean was not found so don't output it
         continue;
       } catch ( IntrospectionException e ) {
         // This is an internal error, something odd happened with reflection so
         // log it and don't output the bean.
         LOG.error("Problem while trying to process JMX query: " + qry
             + " with MBean " + oname, e);
         continue;
       } catch ( ReflectionException e ) {
         // This happens when the code inside the JMX bean threw an exception, so
         // log it and don't output the bean.
         LOG.error("Problem while trying to process JMX query: " + qry
             + " with MBean " + oname, e);
         continue;
       }

       jg.writeStartObject();
       jg.writeStringField("name", oname.toString());

       jg.writeStringField("modelerType", code);
       if ((attribute != null) && (attributeinfo == null)) {
         jg.writeStringField("result", "ERROR");
         jg.writeStringField("message", "No attribute with name " + attribute
             + " was found.");
         jg.writeEndObject();
         jg.writeEndArray();
         jg.close();
         response.setStatus(HttpServletResponse.SC_NOT_FOUND);
         return;
       }

       if (attribute != null) {
         writeAttribute(jg, attribute, attributeinfo);
       } else {
         MBeanAttributeInfo attrs[] = minfo.getAttributes();
         for (int i = 0; i < attrs.length; i++) {
           writeAttribute(jg, oname, attrs[i]);
         }
       }
       jg.writeEndObject();
     }
     jg.writeEndArray();
   }

   private void writeAttribute(JsonGenerator jg, ObjectName oname, MBeanAttributeInfo attr) throws IOException {
     if (!attr.isReadable()) {
       return;
     }
     String attName = attr.getName();
     if ("modelerType".equals(attName)) {
       return;
     }
     if (attName.indexOf("=") >= 0 || attName.indexOf(":") >= 0
         || attName.indexOf(" ") >= 0) {
       return;
     }
     Object value = null;
     try {
       value = mBeanServer.getAttribute(oname, attName);
     } catch (RuntimeMBeanException e) {
       // UnsupportedOperationExceptions happen in the normal course of business,
       // so no need to log them as errors all the time.
       if (e.getCause() instanceof UnsupportedOperationException) {
         LOG.debug("getting attribute "+attName+" of "+oname+" threw an exception", e);
       } else {
         LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
       }
       return;
     } catch (RuntimeErrorException e) {
       // RuntimeErrorException happens when an unexpected failure occurs in getAttribute
       // for example https://issues.apache.org/jira/browse/DAEMON-120
       LOG.debug("getting attribute "+attName+" of "+oname+" threw an exception", e);
       return;
     } catch (AttributeNotFoundException e) {
       //Ignored the attribute was not found, which should never happen because the bean
       //just told us that it has this attribute, but if this happens just don't output
       //the attribute.
       return;
     } catch (MBeanException e) {
       //The code inside the attribute getter threw an exception so log it, and
       // skip outputting the attribute
       LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
       return;
     } catch (RuntimeException e) {
       //For some reason even with an MBeanException available to them Runtime exceptions
       //can still find their way through, so treat them the same as MBeanException
       LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
       return;
     } catch (ReflectionException e) {
       //This happens when the code inside the JMX bean (setter?? from the java docs)
       //threw an exception, so log it and skip outputting the attribute
       LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
       return;
     } catch (InstanceNotFoundException e) {
       //Ignored the mbean itself was not found, which should never happen because we
       //just accessed it (perhaps something unregistered in-between) but if this
       //happens just don't output the attribute.
       return;
     }

     writeAttribute(jg, attName, value);
   }

   private void writeAttribute(JsonGenerator jg, String attName, Object value) throws IOException {
     jg.writeFieldName(attName);
     writeObject(jg, value);
   }

   private void writeObject(JsonGenerator jg, Object value) throws IOException {
     if(value == null) {
       jg.writeNull();
     } else {
       Class<?> c = value.getClass();
       if (c.isArray()) {
         jg.writeStartArray();
         int len = Array.getLength(value);
         for (int j = 0; j < len; j++) {
           Object item = Array.get(value, j);
           writeObject(jg, item);
         }
         jg.writeEndArray();
       } else if(value instanceof Number) {
         Number n = (Number)value;
         jg.writeNumber(n.toString());
       } else if(value instanceof Boolean) {
         Boolean b = (Boolean)value;
         jg.writeBoolean(b);
       } else if(value instanceof CompositeData) {
         CompositeData cds = (CompositeData)value;
         CompositeType comp = cds.getCompositeType();
         Set<String> keys = comp.keySet();
         jg.writeStartObject();
         for(String key: keys) {
           writeAttribute(jg, key, cds.get(key));
         }
         jg.writeEndObject();
       } else if(value instanceof TabularData) {
         TabularData tds = (TabularData)value;
         jg.writeStartArray();
         for(Object entry : tds.values()) {
           writeObject(jg, entry);
         }
         jg.writeEndArray();
       } else {
         jg.writeString(value.toString());
       }
     }
   }
 }
	/*
	* Licensed to the Apache Software Foundation (ASF) under one or more
	* contributor license agreements. See the NOTICE file distributed with
	* this work for additional information regarding copyright ownership.
	* The ASF licenses this file to You under the Apache License, Version 2.0
	* (the "License"); you may not use this file except in compliance with
	* the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package org.apache.hadoop.jmx;

	import org.apache.hadoop.http.HttpServer2;
	import org.codehaus.jackson.JsonFactory;
	import org.codehaus.jackson.JsonGenerator;
	import org.slf4j.Logger;
	import org.slf4j.LoggerFactory;

	import javax.management.AttributeNotFoundException;
	import javax.management.InstanceNotFoundException;
	import javax.management.IntrospectionException;
	import javax.management.MBeanAttributeInfo;
	import javax.management.MBeanException;
	import javax.management.MBeanInfo;
	import javax.management.MBeanServer;
	import javax.management.MalformedObjectNameException;
	import javax.management.ObjectName;
	import javax.management.ReflectionException;
	import javax.management.RuntimeErrorException;
	import javax.management.RuntimeMBeanException;
	import javax.management.openmbean.CompositeData;
	import javax.management.openmbean.CompositeType;
	import javax.management.openmbean.TabularData;
	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.PrintWriter;
	import java.lang.management.ManagementFactory;
	import java.lang.reflect.Array;
	import java.util.Iterator;
	import java.util.Set;

	/*
	* This servlet is based off of the JMXProxyServlet from Tomcat 7.0.14. It has
	* been rewritten to be read only and to output in a JSON format so it is not
	* really that close to the original.
	*/
	/**
	* Provides Read only web access to JMX.
	* <p>
	* This servlet generally will be placed under the /jmx URL for each
	* HttpServer. It provides read only
	* access to JMX metrics. The optional <code>qry</code> parameter
	* may be used to query only a subset of the JMX Beans. This query
	* functionality is provided through the
	* {@link MBeanServer#queryNames(ObjectName, javax.management.QueryExp)}
	* method.
	* <p>
	* For example <code>http://.../jmx?qry=Hadoop:*</code> will return
	* all hadoop metrics exposed through JMX.
	* <p>
	* The optional <code>get</code> parameter is used to query an specific
	* attribute of a JMX bean. The format of the URL is
	* <code>http://.../jmx?get=MXBeanName::AttributeName<code>
	* <p>
	* For example
	* <code>
	* http://../jmx?get=Hadoop:service=NameNode,name=NameNodeInfo::ClusterId
	* </code> will return the cluster id of the namenode mxbean.
	* <p>
	* If the <code>qry</code> or the <code>get</code> parameter is not formatted
	* correctly then a 400 BAD REQUEST http response code will be returned.
	* <p>
	* If a resouce such as a mbean or attribute can not be found,
	* a 404 SC_NOT_FOUND http response code will be returned.
	* <p>
	* The return format is JSON and in the form
	* <p>
	* <code><pre>
	* {
	* "beans" : [
	* {
	* "name":"bean-name"
	* ...
	* }
	* ]
	* }
	* </pre></code>
	* <p>
	* The servlet attempts to convert the the JMXBeans into JSON. Each
	* bean's attributes will be converted to a JSON object member.
	*
	* If the attribute is a boolean, a number, a string, or an array
	* it will be converted to the JSON equivalent.
	*
	* If the value is a {@link CompositeData} then it will be converted
	* to a JSON object with the keys as the name of the JSON member and
	* the value is converted following these same rules.
	*
	* If the value is a {@link TabularData} then it will be converted
	* to an array of the {@link CompositeData} elements that it contains.
	*
	* All other objects will be converted to a string and output as such.
	*
	* The bean's name and modelerType will be returned for all beans.
	*
	*/
	public class JMXJsonServlet extends HttpServlet {
	private static final Logger LOG =
	LoggerFactory.getLogger(JMXJsonServlet.class);
	static final String ACCESS_CONTROL_ALLOW_METHODS =
	"Access-Control-Allow-Methods";
	static final String ACCESS_CONTROL_ALLOW_ORIGIN =
	"Access-Control-Allow-Origin";

	private static final long serialVersionUID = 1L;

	/**
	* MBean server.
	*/
	protected transient MBeanServer mBeanServer = null;

	// --------------------------------------------------------- Public Methods
	/**
	* Initialize this servlet.
	*/
	@Override
	public void init() throws ServletException {
	// Retrieve the MBean server
	mBeanServer = ManagementFactory.getPlatformMBeanServer();
	}

	protected boolean isInstrumentationAccessAllowed(HttpServletRequest request,
	HttpServletResponse response) throws IOException {
	return HttpServer2.isInstrumentationAccessAllowed(getServletContext(),
	request, response);
	}

	/**
	* Disable TRACE method to avoid TRACE vulnerability.
	*/
	@Override
	protected void doTrace(HttpServletRequest req, HttpServletResponse resp)
	throws ServletException, IOException {
	resp.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED);
	}

	/**
	* Process a GET request for the specified resource.
	*
	* @param request
	* The servlet request we are processing
	* @param response
	* The servlet response we are creating
	*/
	@Override
	public void doGet(HttpServletRequest request, HttpServletResponse response) {
	String jsonpcb = null;
	PrintWriter writer = null;
	try {
	if (!isInstrumentationAccessAllowed(request, response)) {
	return;
	}

	JsonGenerator jg = null;
	try {
	writer = response.getWriter();

	response.setContentType("application/json; charset=utf8");
	response.setHeader(ACCESS_CONTROL_ALLOW_METHODS, "GET");
	response.setHeader(ACCESS_CONTROL_ALLOW_ORIGIN, "*");

	JsonFactory jsonFactory = new JsonFactory();
	jg = jsonFactory.createJsonGenerator(writer);
	jg.disable(JsonGenerator.Feature.AUTO_CLOSE_TARGET);
	jg.useDefaultPrettyPrinter();
	jg.writeStartObject();

	if (mBeanServer == null) {
	jg.writeStringField("result", "ERROR");
	jg.writeStringField("message", "No MBeanServer could be found");
	jg.close();
	LOG.error("No MBeanServer could be found.");
	response.setStatus(HttpServletResponse.SC_NOT_FOUND);
	return;
	}

	// query per mbean attribute
	String getmethod = request.getParameter("get");
	if (getmethod != null) {
	String[] splitStrings = getmethod.split("\\:\\:");
	if (splitStrings.length != 2) {
	jg.writeStringField("result", "ERROR");
	jg.writeStringField("message", "query format is not as expected.");
	jg.close();
	response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
	return;
	}
	listBeans(jg, new ObjectName(splitStrings[0]), splitStrings[1],
	response);
	jg.close();
	return;

	}

	// query per mbean
	String qry = request.getParameter("qry");
	if (qry == null) {
	qry = ":";
	}
	listBeans(jg, new ObjectName(qry), null, response);
	} finally {
	if (jg != null) {
	jg.close();
	}
	if (writer != null) {
	writer.close();
	}
	}
	} catch ( IOException e ) {
	LOG.error("Caught an exception while processing JMX request", e);
	response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
	} catch ( MalformedObjectNameException e ) {
	LOG.error("Caught an exception while processing JMX request", e);
	response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
	} finally {
	if (writer != null) {
	writer.close();
	}
	}
	}

	// --------------------------------------------------------- Private Methods
	private void listBeans(JsonGenerator jg, ObjectName qry, String attribute,
	HttpServletResponse response)
	throws IOException {
	LOG.debug("Listing beans for "+qry);
	Set<ObjectName> names = null;
	names = mBeanServer.queryNames(qry, null);

	jg.writeArrayFieldStart("beans");
	Iterator<ObjectName> it = names.iterator();
	while (it.hasNext()) {
	ObjectName oname = it.next();
	MBeanInfo minfo;
	String code = "";
	Object attributeinfo = null;
	try {
	minfo = mBeanServer.getMBeanInfo(oname);
	code = minfo.getClassName();
	String prs = "";
	try {
	if ("org.apache.commons.modeler.BaseModelMBean".equals(code)) {
	prs = "modelerType";
	code = (String) mBeanServer.getAttribute(oname, prs);
	}
	if (attribute!=null) {
	prs = attribute;
	attributeinfo = mBeanServer.getAttribute(oname, prs);
	}
	} catch (AttributeNotFoundException e) {
	// If the modelerType attribute was not found, the class name is used
	// instead.
	LOG.error("getting attribute " + prs + " of " + oname
	+ " threw an exception", e);
	} catch (MBeanException e) {
	// The code inside the attribute getter threw an exception so log it,
	// and fall back on the class name
	LOG.error("getting attribute " + prs + " of " + oname
	+ " threw an exception", e);
	} catch (RuntimeException e) {
	// For some reason even with an MBeanException available to them
	// Runtime exceptionscan still find their way through, so treat them
	// the same as MBeanException
	LOG.error("getting attribute " + prs + " of " + oname
	+ " threw an exception", e);
	} catch ( ReflectionException e ) {
	// This happens when the code inside the JMX bean (setter?? from the
	// java docs) threw an exception, so log it and fall back on the
	// class name
	LOG.error("getting attribute " + prs + " of " + oname
	+ " threw an exception", e);
	}
	} catch (InstanceNotFoundException e) {
	//Ignored for some reason the bean was not found so don't output it
	continue;
	} catch ( IntrospectionException e ) {
	// This is an internal error, something odd happened with reflection so
	// log it and don't output the bean.
	LOG.error("Problem while trying to process JMX query: " + qry
	+ " with MBean " + oname, e);
	continue;
	} catch ( ReflectionException e ) {
	// This happens when the code inside the JMX bean threw an exception, so
	// log it and don't output the bean.
	LOG.error("Problem while trying to process JMX query: " + qry
	+ " with MBean " + oname, e);
	continue;
	}

	jg.writeStartObject();
	jg.writeStringField("name", oname.toString());

	jg.writeStringField("modelerType", code);
	if ((attribute != null) && (attributeinfo == null)) {
	jg.writeStringField("result", "ERROR");
	jg.writeStringField("message", "No attribute with name " + attribute
	+ " was found.");
	jg.writeEndObject();
	jg.writeEndArray();
	jg.close();
	response.setStatus(HttpServletResponse.SC_NOT_FOUND);
	return;
	}

	if (attribute != null) {
	writeAttribute(jg, attribute, attributeinfo);
	} else {
	MBeanAttributeInfo attrs[] = minfo.getAttributes();
	for (int i = 0; i < attrs.length; i++) {
	writeAttribute(jg, oname, attrs[i]);
	}
	}
	jg.writeEndObject();
	}
	jg.writeEndArray();
	}

	private void writeAttribute(JsonGenerator jg, ObjectName oname, MBeanAttributeInfo attr) throws IOException {
	if (!attr.isReadable()) {
	return;
	}
	String attName = attr.getName();
	if ("modelerType".equals(attName)) {
	return;
	}
	if (attName.indexOf("=") >= 0 \|\| attName.indexOf(":") >= 0
	\|\| attName.indexOf(" ") >= 0) {
	return;
	}
	Object value = null;
	try {
	value = mBeanServer.getAttribute(oname, attName);
	} catch (RuntimeMBeanException e) {
	// UnsupportedOperationExceptions happen in the normal course of business,
	// so no need to log them as errors all the time.
	if (e.getCause() instanceof UnsupportedOperationException) {
	LOG.debug("getting attribute "+attName+" of "+oname+" threw an exception", e);
	} else {
	LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
	}
	return;
	} catch (RuntimeErrorException e) {
	// RuntimeErrorException happens when an unexpected failure occurs in getAttribute
	// for example https://issues.apache.org/jira/browse/DAEMON-120
	LOG.debug("getting attribute "+attName+" of "+oname+" threw an exception", e);
	return;
	} catch (AttributeNotFoundException e) {
	//Ignored the attribute was not found, which should never happen because the bean
	//just told us that it has this attribute, but if this happens just don't output
	//the attribute.
	return;
	} catch (MBeanException e) {
	//The code inside the attribute getter threw an exception so log it, and
	// skip outputting the attribute
	LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
	return;
	} catch (RuntimeException e) {
	//For some reason even with an MBeanException available to them Runtime exceptions
	//can still find their way through, so treat them the same as MBeanException
	LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
	return;
	} catch (ReflectionException e) {
	//This happens when the code inside the JMX bean (setter?? from the java docs)
	//threw an exception, so log it and skip outputting the attribute
	LOG.error("getting attribute "+attName+" of "+oname+" threw an exception", e);
	return;
	} catch (InstanceNotFoundException e) {
	//Ignored the mbean itself was not found, which should never happen because we
	//just accessed it (perhaps something unregistered in-between) but if this
	//happens just don't output the attribute.
	return;
	}

	writeAttribute(jg, attName, value);
	}

	private void writeAttribute(JsonGenerator jg, String attName, Object value) throws IOException {
	jg.writeFieldName(attName);
	writeObject(jg, value);
	}

	private void writeObject(JsonGenerator jg, Object value) throws IOException {
	if(value == null) {
	jg.writeNull();
	} else {
	Class<?> c = value.getClass();
	if (c.isArray()) {
	jg.writeStartArray();
	int len = Array.getLength(value);
	for (int j = 0; j < len; j++) {
	Object item = Array.get(value, j);
	writeObject(jg, item);
	}
	jg.writeEndArray();
	} else if(value instanceof Number) {
	Number n = (Number)value;
	jg.writeNumber(n.toString());
	} else if(value instanceof Boolean) {
	Boolean b = (Boolean)value;
	jg.writeBoolean(b);
	} else if(value instanceof CompositeData) {
	CompositeData cds = (CompositeData)value;
	CompositeType comp = cds.getCompositeType();
	Set<String> keys = comp.keySet();
	jg.writeStartObject();
	for(String key: keys) {
	writeAttribute(jg, key, cds.get(key));
	}
	jg.writeEndObject();
	} else if(value instanceof TabularData) {
	TabularData tds = (TabularData)value;
	jg.writeStartArray();
	for(Object entry : tds.values()) {
	writeObject(jg, entry);
	}
	jg.writeEndArray();
	} else {
	jg.writeString(value.toString());
	}
	}
	}
	}