public class JMXJsonServlet
extends javax.servlet.http.HttpServlet

Provides Read only web access to JMX.

This servlet generally will be placed under the /jmx URL for each HttpServer. It provides read only access to JMX metrics. The optional qry parameter may be used to query only a subset of the JMX Beans. This query functionality is provided through the MBeanServer.queryNames(ObjectName, javax.management.QueryExp) method.

For example http://.../jmx?qry=Hadoop:* will return all hadoop metrics exposed through JMX.

The optional get parameter is used to query an specific attribute of a JMX bean. The format of the URL is http://.../jmx?get=MXBeanName::AttributeName

For example http://../jmx?get=Hadoop:service=NameNode,name=NameNodeInfo::ClusterId will return the cluster id of the namenode mxbean.

If the qry or the get parameter is not formatted correctly then a 400 BAD REQUEST http response code will be returned.

If a resouce such as a mbean or attribute can not be found, a 404 SC_NOT_FOUND http response code will be returned.

The return format is JSON and in the form

  {
    "beans" : [
      {
        "name":"bean-name"
        ...
      }
    ]
  }
  

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 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 TabularData then it will be converted to an array of the 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. Optional paramater "callback" should be used to deliver JSONP response.