Tomcat example source code file (JMXProxyServlet.java)

This example Tomcat source code file (JMXProxyServlet.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Tomcat tags/keywords

attribute, error, error, exception, exception, http, management, object, objectname, objectname, ok, printwriter, request, response, servlet, servletexception, string, string, stringbuffer, util

The Tomcat JMXProxyServlet.java source code

/*
 * 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.catalina.manager;


import java.io.IOException;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.Set;
import javax.management.MBeanServer;
import javax.management.ObjectName;
import javax.management.MBeanInfo;
import javax.management.MBeanAttributeInfo;
import javax.management.Attribute;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.tomcat.util.modeler.Registry;

/**
 * This servlet will dump JMX attributes in a simple format
 * and implement proxy services for modeler.
 *
 * @author Costin Manolache
 */
public class JMXProxyServlet extends HttpServlet  {
    // ----------------------------------------------------- Instance Variables

    /**
     * MBean server.
     */
    protected MBeanServer mBeanServer = null;
    protected Registry registry;
    // --------------------------------------------------------- Public Methods


    /**
     * Initialize this servlet.
     */
    public void init() throws ServletException {
        // Retrieve the MBean server
        registry = Registry.getRegistry(null, null);
        mBeanServer = Registry.getRegistry(null, null).getMBeanServer();
    }


    /**
     * Process a GET request for the specified resource.
     *
     * @param request The servlet request we are processing
     * @param response The servlet response we are creating
     *
     * @exception IOException if an input/output error occurs
     * @exception ServletException if a servlet-specified error occurs
     */
    public void doGet(HttpServletRequest request,
                      HttpServletResponse response)
        throws IOException, ServletException
    {

        response.setContentType("text/plain");

        PrintWriter writer = response.getWriter();

        if( mBeanServer==null ) {
            writer.println("Error - No mbean server");
            return;
        }

        String qry=request.getParameter("set");
        if( qry!= null ) {
            String name=request.getParameter("att");
            String val=request.getParameter("val");

            setAttribute( writer, qry, name, val );
            return;
        }
        qry=request.getParameter("get");
        if( qry!= null ) {
            String name=request.getParameter("att");
            getAttribute( writer, qry, name );
            return;
        }        
        qry=request.getParameter("qry");
        if( qry == null ) {
            qry = "*:*";
        }

        listBeans( writer, qry );

    }

    public void getAttribute(PrintWriter writer, String onameStr, String att) {
        try {
            ObjectName oname = new ObjectName(onameStr);
            Object value = mBeanServer.getAttribute(oname, att);
            writer.println("OK - Attribute get '" + onameStr + "' - " + att
                    + "= " + escape(value.toString()));
        } catch (Exception ex) {
            writer.println("Error - " + ex.toString());
        }
    }

    public void setAttribute( PrintWriter writer,
                              String onameStr, String att, String val )
    {
        try {
            ObjectName oname=new ObjectName( onameStr );
            String type=registry.getType(oname, att);
            Object valueObj=registry.convertValue(type, val );
            mBeanServer.setAttribute( oname, new Attribute(att, valueObj));
            writer.println("OK - Attribute set");
        } catch( Exception ex ) {
            writer.println("Error - " + ex.toString());
        }
    }

    public void listBeans( PrintWriter writer, String qry )
    {

        Set names = null;
        try {
            names=mBeanServer.queryNames(new ObjectName(qry), null);
            writer.println("OK - Number of results: " + names.size());
            writer.println();
        } catch (Exception e) {
            writer.println("Error - " + e.toString());
            return;
        }

        Iterator it=names.iterator();
        while( it.hasNext()) {
            ObjectName oname=(ObjectName)it.next();
            writer.println( "Name: " + oname.toString());

            try {
                MBeanInfo minfo=mBeanServer.getMBeanInfo(oname);
                // can't be null - I thinl
                String code=minfo.getClassName();
                if ("org.apache.commons.modeler.BaseModelMBean".equals(code)) {
                    code=(String)mBeanServer.getAttribute(oname, "modelerType");
                }
                writer.println("modelerType: " + code);

                MBeanAttributeInfo attrs[]=minfo.getAttributes();
                Object value=null;

                for( int i=0; i< attrs.length; i++ ) {
                    if( ! attrs[i].isReadable() ) continue;
                    if( ! isSupported( attrs[i].getType() )) continue;
                    String attName=attrs[i].getName();
                    if( attName.indexOf( "=") >=0 ||
                            attName.indexOf( ":") >=0 ||
                            attName.indexOf( " ") >=0 ) {
                        continue;
                    }
            
                    try {
                        value=mBeanServer.getAttribute(oname, attName);
                    } catch( Throwable t) {
                        log("Error getting attribute " + oname +
                            " " + attName + " " + t.toString());
                        continue;
                    }
                    if( value==null ) continue;
                    if( "modelerType".equals( attName)) continue;
                    String valueString=value.toString();
                    writer.println( attName + ": " + escape(valueString));
                }
            } catch (Exception e) {
                // Ignore
            }
            writer.println();
        }

    }

    public String escape(String value) {
        // The only invalid char is \n
        // We also need to keep the string short and split it with \nSPACE
        // XXX TODO
        int idx=value.indexOf( "\n" );
        if( idx < 0 ) return value;

        int prev=0;
        StringBuffer sb=new StringBuffer();
        while( idx >= 0 ) {
            appendHead(sb, value, prev, idx);

            sb.append( "\\n\n ");
            prev=idx+1;
            if( idx==value.length() -1 ) break;
            idx=value.indexOf('\n', idx+1);
        }
        if( prev < value.length() )
            appendHead( sb, value, prev, value.length());
        return sb.toString();
    }

    private void appendHead( StringBuffer sb, String value, int start, int end) {
        if (end < 1) return;

        int pos=start;
        while( end-pos > 78 ) {
            sb.append( value.substring(pos, pos+78));
            sb.append( "\n ");
            pos=pos+78;
        }
        sb.append( value.substring(pos,end));
    }

    public boolean isSupported( String type ) {
        return true;
    }
}