Manager App HOW-TO

Introduction Configuring Manager Application Access Supported Manager Commands Deploy A New Application Remotely Deploy A New Application from a Local Path List Currently Deployed Applications Reload An Existing Application List OS and JVM Properties List Available Global JNDI Resources List Available Security Roles Session Statistics Start an Existing Application Stop an Existing Application Undeploy an Existing Application Server Status Executing Manager Commands With Ant Tasks output capture Using the JMX Proxy Servlet What is JMX Proxy Servlet JMX Query command JMX Set command

Introduction

In many production environments, it is very useful to have the capability to deploy a new web application, or undeploy an existing one, without having to shut down and restart the entire container. In addition, you can request an existing application to reload itself, even if you have not declared it to bereloadable in the Tomcat 5 server configuration file. To support these capabilities, Tomcat 5 includes a web application (installed by default on context path /manager) that supports the following functions: Deploy a new web application from the uploaded contents of a WAR file. Deploy a new web application, on a specified context path, from the server file system. List the currently deployed web applications, as well as the sessions that are currently active for those web apps. Reload an existing web application, to reflect changes in the contents of /WEB-INF/classes or /WEB-INF/lib. List the OS and JVM property values. List the available global JNDI resources, for use in deployment tools that are preparing  elements nested in a deployment description. List the available security roles defined in the user database. Start a stopped application (thus making it available again). Stop an existing application (so that it becomes unavailable), but do not undeploy it. Undeploy a deployed web application and delete its document base directory (unless it was deployed from file system). A default Tomcat installation includes the manager. To add an instance of the Manager web application Context to a new host install themanager.xml context configuration file in the $CATALINA_HOME/conf/[enginename]/[hostname] folder. Here is an example: If you have Tomcat configured to support multiple virtual hosts (websites) you would need to configure a Manager for each. There are three ways to use the Manager web application. As an application with a user interface you use in your browser. Here is an example URL where you can replace localhost with your website host name: http://localhost/manager/html/ . A minimal version using HTTP requests only which is suitable for use by scripts setup by system administrators. Commands are given as part of the request URI, and responses are in the form of simple text that can be easily parsed and processed. See Supported Manager Commands for more information. A convenient set of task definitions for the Ant (version 1.4 or later) build tool. See Executing Manager Commands With Ant for more information.

Configuring Manager Application Access

The description below uses the variable name $CATALINA_HOME to refer to the directory into which you have installed Tomcat 5, and is the base directory against which most relative paths are resolved. However, if you have configured Tomcat 5 for multiple instances by setting a CATALINA_BASE directory, you should use $CATALINA_BASE instead of $CATALINA_HOME for each of these references. It would be quite unsafe to ship Tomcat with default settings that allowed anyone on the Internet to execute the Manager application on your server. Therefore, the Manager application is shipped with the requirement that anyone who attempts to use it must authenticate themselves, using a username and password that have the role manager associated with them. Further, there is no username in the default users file ($CATALINA_HOME/conf/tomcat-users.xml) that is assigned this role. Therefore, access to the Manager application is completely disabled by default. To enable access to the Manager web application, you must either create a new username/password combination and associate the role namemanager with it, or add the manager role to some existing username/password combination. Exactly where this is done depends on which Realmimplementation you are using: MemoryRealm - If you have not customized your $CATALINA_HOME/conf/server.xml to select a different one, Tomcat 5 defaults to an XML-format file stored at $CATALINA_HOME/conf/tomcat-users.xml, which can be edited with any text editor. This file contains an XML for each individual user, which might look something like this: which defines the username and password used by this individual to log on, and the role names he or she is associated with. You can add themanager role to the comma-delimited roles attribute for one or more existing users, and/or create new users with that assigned role. JDBCRealm - Your user and role information is stored in a database accessed via JDBC. Add the manager role to one or more existing users, and/or create one or more new users with this role assigned, following the standard procedures for your environment. JNDIRealm - Your user and role information is stored in a directory server accessed via LDAP. Add the manager role to one or more existing users, and/or create one or more new users with this role assigned, following the standard procedures for your environment. The first time you attempt to issue one of the Manager commands described in the next section, you will be challenged to log on using BASIC authentication. The username and password you enter do not matter, as long as they identify a valid user in the users database who possesses the rolemanager. In addition to the password restrictions the manager web application could be restricted by the remote IP address or host by adding aRemoteAddrValve or RemoteHostValve. Here is an example of restricting access to the localhost by IP address:

Supported Manager Commands

All commands that the Manager application knows how to process are specified in a single request URI like this: http://{host}:{port}/manager/{command}?{parameters} where {host} and {port} represent the hostname and port number on which Tomcat is running, {command} represents the Manager command you wish to execute, and {parameters} represents the query parameters that are specific to that command. In the illustrations below, customize the host and port appropriately for your installation. Most commands accept one or more of the following query parameters: path - The context path (including the leading slash) of the web application you are dealing with. To select the ROOT web application, specify "/". NOTE - It is not possible to perform administrative commands on the Manager application itself. war - URL of a web application archive (WAR) file, pathname of a directory which contains the web application, or a Context configuration ".xml" file. You can use URLs in any of the following formats: file:/absolute/path/to/a/directory - The absolute path of a directory that contains the unpacked version of a web application. This directory will be attached to the context path you specify without any changes. file:/absolute/path/to/a/webapp.war - The absolute path of a web application archive (WAR) file. This is valid only for the /deploycommand, and is the only acceptable format to that command. jar:file:/absolute/path/to/a/warfile.war!/ - The URL to a local web application archive (WAR) file. You can use any syntax that is valid for the JarURLConnection class for reference to an entire JAR file. file:/absolute/path/to/a/context.xml - The absolute path of a web application Context configuration ".xml" file which contains the Context configuration element. directory - The directory name for the web application context in the Host's application base directory. webapp.war - The name of a web application war file located in the Host's application base directory. Each command will return a response in text/plain format (i.e. plain ASCII with no HTML markup), making it easy for both humans and programs to read). The first line of the response will begin with either OK or FAIL, indicating whether the requested command was successful or not. In the case of failure, the rest of the first line will contain a description of the problem that was encountered. Some commands include additional lines of information as described below. Internationalization Note - The Manager application looks up its message strings in resource bundles, so it is possible that the strings have been translated for your platform. The examples below show the English version of the messages. WARNING: the legacy commands /install and /remove are deprecated. They are presently equivalent to /deploy and/undeploy, but could be removed in a future release. Deploy A New Application Remotely http://localhost:8080/manager/deploy Upload the web application archive (WAR) file that is specified as the request data in this HTTP PUT request, install it into the appBasedirectory of our corresponding virtual host, and start it using the war file name without the .war extension as the path. The application can later be undeployed (and the corresponding application directory removed) by use of the /undeploy. To deploy the ROOT web application (the application with a context path of "/"), name the war ROOT.war. The .WAR file may include Tomcat specific deployment configuration, by including a Context configuration XML file in /META-INF/context.xml. URL parameters include: update: When set to true, any existing update will be undeployed first. The default value is set to false. tag: Specifying a tag name, this allows associating the deployed webapp with a version number. The application version can be later redeployed when needed using only the tag. NOTE - This command is the logical opposite of the /undeploy command. If installation and startup is successful, you will receive a response like this: OK - Deployed application at context path /foo Otherwise, the response will start with FAIL and include an error message. Possible causes for problems include: Application already exists at path /foo The context paths for all currently running web applications must be unique. Therefore, you must undeploy the existing web application using this context path, or choose a different context path for the new one. The updateparameter may be specified as a parameter on the URL, with a value of true to avoid this error. In that case, an undeploy will be performed on an existing application before performing the deployment. Encountered exception An exception was encountered trying to start the new web application. Check the Tomcat 5 logs for the details, but likely explanations include problems parsing your /WEB-INF/web.xml file, or missing classes encountered when initializing application event listeners and filters. Deploy A New Application from a Local Path Deploy and start a new web application, attached to the specified context path (which must not be in use by any other web application). This command is the logical opposite of the /undeploy command. There are a number of different ways the deploy command can be used. Deploy a version of a previously deployed webapp This can be used to deploy a previous version of a web application, which has been deployed using the tag attribute. Note that the work directory for the manager webapp will contain the previously deployed WARs; removing it would make the deployment fail. http://localhost:8080/manager/deploy?path=/footoo&tag=footag Deploy a Directory or WAR by URL Deploy a web application directory or ".war" file located on the Tomcat server. If no path is specified, the directory name or the war file name without the ".war" extension is used as the path. The war parameter specifies a URL (including the file: scheme) for either a directory or a web application archive (WAR) file. The supported syntax for a URL referring to a WAR file is described on the Javadocs page for the java.net.JarURLConnection class. Use only URLs that refer to the entire WAR file. In this example the web application located in the directory /path/to/foo on the Tomcat server is deployed as the web application context named /footoo. http://localhost:8080/manager/deploy?path=/footoo&war=file:/path/to/foo In this example the ".war" file /path/to/bar.war on the Tomcat server is deployed as the web application context named /bar. Notice that there is no path parameter so the context path defaults to the name of the web application archive file without the ".war" extension. http://localhost:8080/manager/deploy?war=jar:file:/path/to/bar.war!/ Deploy a Directory or War from the Host appBase Deploy a web application directory or ".war" file located in your Host appBase directory. The directory name or the war file name without the ".war" extension is used as the path. In this example the web application located in a sub directory named foo in the Host appBase directory of the Tomcat server is deployed as the web application context named /foo. Notice that the context path used is the name of the web application directory. http://localhost:8080/manager/deploy?war=foo In this example the ".war" file bar.war located in your Host appBase directory on the Tomcat server is deployed as the web application context named /bar. http://localhost:8080/manager/deploy?war=bar.war Deploy using a Context configuration ".xml" file If the Host deployXML flag is set to true you can deploy a web application using a Context configuration ".xml" file and an optional ".war" file or web application directory. The context path is not used when deploying a web application using a context ".xml" configuration file. A Context configuration ".xml" file can contain valid XML for a web application Context just as if it were configured in your Tomcatserver.xml configuration file. Here is an example: When the optional war parameter is set to the URL for a web application ".war" file or directory it overrides any docBase configured in the context configuration ".xml" file. Here is an example of deploying an application using a Context configuration ".xml" file. http://localhost:8080/manager/deploy?config=file:/path/context.xml Here is an example of deploying an application using a Context configuration ".xml" file and a web application ".war" file located on the server. http://localhost:8080/manager/deploy?config=file:/path/context.xml&war=file:/path/bar.war&path=/bar Deployment Notes If the Host is configured with unpackWARs=true and you deploy a war file, the war will be unpacked into a directory in your Host appBase directory. If the application war or directory is installed in your Host appBase directory and either the Host is configured with autoDeploy=true or liveDeploy=true, the Context path must match the directory name or war file name without the ".war" extension. For security when untrusted users can manage web applications, the Host deployXML flag can be set to false. This prevents untrusted users from deploying web applications using a configuration XML file and also prevents them from deploying application directories or ".war" files located outside of their Host appBase. Deploy Response If installation and startup is successful, you will receive a response like this: OK - Deployed application at context path /foo Otherwise, the response will start with FAIL and include an error message. Possible causes for problems include: Application already exists at path /foo The context paths for all currently running web applications must be unique. Therefore, you must undeploy the existing web application using this context path, or choose a different context path for the new one. The updateparameter may be specified as a parameter on the URL, with a value of true to avoid this error. In that case, an undeploy will be performed on an existing application before performing the deployment. Document base does not exist or is not a readable directory The URL specified by the war parameter must identify a directory on this server that contains the "unpacked" version of a web application, or the absolute URL of a web application archive (WAR) file that contains this application. Correct the value specified by the war parameter. Encountered exception An exception was encountered trying to start the new web application. Check the Tomcat 5 logs for the details, but likely explanations include problems parsing your /WEB-INF/web.xml file, or missing classes encountered when initializing application event listeners and filters. Invalid application URL was specified The URL for the directory or web application that you specified was not valid. Such URLs must start with file:, and URLs for a WAR file must end in ".war". Invalid context path was specified The context path must start with a slash character. To reference the ROOT web application use "/". Context path must match the directory or WAR file name: If the application war or directory is installed in your Host appBase directory and either the Host is configured with autoDeploy=true or liveDeploy=true, the Context path must match the directory name or war file name without the ".war" extension. Only web applications in the Host web application directory can be installed If the Host deployXML flag is set to false this error will happen if an attempt is made to deploy a web application directory or ".war" file outside of the Host appBase directory. List Currently Deployed Applications http://localhost:8080/manager/list List the context paths, current status (running or stopped), and number of active sessions for all currently deployed web applications. A typical response immediately after starting Tomcat might look like this: OK - Listed applications for virtual host localhost /webdav:running:0 /examples:running:0 /manager:running:0 /:running:0 Reload An Existing Application http://localhost:8080/manager/reload?path=/examples Signal an existing application to shut itself down and reload. This can be useful when the web application context is not reloadable and you have updated classes or property files in the /WEB-INF/classes directory or when you have added or updated jar files in the/WEB-INF/lib directory. NOTE: The /WEB-INF/web.xml web application configuration file is not reread on a reload. If you have made changes to your web.xml file you must stop then start the web application. If this command succeeds, you will see a response like this: OK - Reloaded application at context path /examples Otherwise, the response will start with FAIL and include an error message. Possible causes for problems include: Encountered exception An exception was encountered trying to restart the web application. Check the Tomcat 5 logs for the details. Invalid context path was specified The context path must start with a slash character. To reference the ROOT web application use "/". No context exists for path /foo There is no deployed application on the context path that you specified. No context path was specified The  path parameter is required. Reload not supported on WAR deployed at path /foo Currently, application reloading (to pick up changes to the classes or  web.xml file) is not supported when a web application is deployed directly from a WAR file. It only works when the web application is deployed from an unpacked directory. If you are using a WAR file, you should  undeploy and then  deploy or  deploy with the update parameter the application again to pick up your changes. List OS and JVM Properties http://localhost:8080/manager/serverinfo Lists information about the Tomcat version, OS, and JVM properties. If an error occurs, the response will start with FAIL and include an error message. Possible causes for problems include: Encountered exception An exception was encountered trying to enumerate the system properties. Check the Tomcat 5 logs for the details. List Available Global JNDI Resources http://localhost:8080/manager/resources[?type=xxxxx] List the global JNDI resources that are available for use in resource links for context configuration files. If you specify the type request parameter, the value must be the fully qualified Java class name of the resource type you are interested in (for example, you would specify javax.sql.DataSource to acquire the names of all available JDBC data sources). If you do not specify the type request parameter, resources of all types will be returned. Depending on whether the type request parameter is specified or not, the first line of a normal response will be: OK - Listed global resources of all types or OK - Listed global resources of type xxxxx followed by one line for each resource. Each line is composed of fields delimited by colon characters (":"), as follows: Global Resource Name - The name of this global JNDI resource, which would be used in the global attribute of a element. Global Resource Type - The fully qualified Java class name of this global JNDI resource. If an error occurs, the response will start with FAIL and include an error message. Possible causes for problems include: Encountered exception An exception was encountered trying to enumerate the global JNDI resources. Check the Tomcat 5 logs for the details. No global JNDI resources are available The Tomcat server you are running has been configured without global JNDI resources. List Available Security Roles http://localhost:8080/manager/roles List the security role names (and corresponding descriptions) that are available in the org.apache.catalina.UserDatabaseresource that is linked to the users resource reference in the web.xml file for the Manager web application. This would typically be used, for example, by a deployment tool that wanted to create  elements to map security role names used in a web application to the role names actually defined within the container. By default, the users resource reference is pointed at the global UserDatabase resource. If you choose to utilize a different user database per virtual host, you should modify the  element in the default manager.xml context configuration file to point at the global user database resource for this virtual host. When this command is executed, the first line of the response will be: OK - Listed security roles followed by one line for each security role. Each line is composed of fields delimited by colon characters (":") as follows: Security Role Name - A security role name that is known to Tomcat in the user database. Description - Description of this security role (useful in creating user interfaces for selecting roles. If an error occurs, the response will start with FAIL and include an error message. Possible causes for problems include: Cannot resolve user database reference - A JNDI error prevented the successful lookup of theorg.apache.catalina.UserDatabase resource. Check the Tomcat log files for a stack trace associated with this error. No user database is available - You have not configured a resource reference for the users resource that points at an appropriate user database instance. Check your manager.xml file and ensure that you have created an appropriate or  element for this resource. Session Statistics http://localhost:8080/manager/sessions?path=/examples Display the default session timeout for a web application, and the number of currently active sessions that fall within ten-minute ranges of their actual timeout times. For example, after restarting Tomcat and then executing one of the JSP samples in the /examples web app, you might get something like this: OK - Session information for application at context path /examples Default maximum session inactive interval 30 minutes 30 - <40 minutes:1 sessions Start an Existing Application http://localhost:8080/manager/start?path=/examples Signal a stopped application to restart, and make itself available again. Stopping and starting is useful, for example, if the database required by your application becomes temporarily unavailable. It is usually better to stop the web application that relies on this database rather than letting users continuously encounter database exceptions. If this command succeeds, you will see a response like this: OK - Started application at context path /examples Otherwise, the response will start with FAIL and include an error message. Possible causes for problems include: Encountered exception An exception was encountered trying to start the web application. Check the Tomcat 5 logs for the details. Invalid context path was specified The context path must start with a slash character. To reference the ROOT web application use "/". No context exists for path /foo There is no deployed application on the context path that you specified. No context path was specified The  path parameter is required. Stop an Existing Application http://localhost:8080/manager/stop?path=/examples Signal an existing application to make itself unavailable, but leave it deployed. Any request that comes in while an application is stopped will see an HTTP error 404, and this application will show as "stopped" on a list applications command. If this command succeeds, you will see a response like this: OK - Stopped application at context path /examples Otherwise, the response will start with FAIL and include an error message. Possible causes for problems include: Encountered exception An exception was encountered trying to stop the web application. Check the Tomcat 5 logs for the details. Invalid context path was specified The context path must start with a slash character. To reference the ROOT web application use "/". No context exists for path /foo There is no deployed application on the context path that you specified. No context path was specified The  path parameter is required. Undeploy an Existing Application http://localhost:8080/manager/undeploy?path=/examples WARNING - This command will delete any web application artifacts that exist within appBase directory (typically "webapps") for this virtual host. This will delete the the application .WAR, if present, the application directory resulting either from a deploy in unpacked form or from .WAR expansion as well as the XML Context definition from$CATALINA_HOME/conf/[enginename]/[hostname]/ directory. If you simply want to take an application out of service, you should use the /stop command instead. Signal an existing application to gracefully shut itself down, and remove it from Tomcat (which also makes this context path available for reuse later). In addition, the document root directory is removed, if it exists in the appBase directory (typically "webapps") for this virtual host. This command is the logical opposite of the /deploy command. If this command succeeds, you will see a response like this: OK - Undeployed application at context path /examples Otherwise, the response will start with FAIL and include an error message. Possible causes for problems include: Encountered exception An exception was encountered trying to undeploy the web application. Check the Tomcat 5 logs for the details. Invalid context path was specified The context path must start with a slash character. To reference the ROOT web application use "/". No context exists for path /foo There is no deployed application on the context path that you specified. No context path was specified The  path parameter is required. Server Status From this link , you can view information about the server. First, you have the server and JVM version number, JVM provider, OS name and number followed by the architecture type. Second, there is several information about the memory usage of the JVM (available, total and max memory). Then, there is information about the Tomcat AJP and HTTP connectors. The same information is available for both of them : Threads information : Max threads, min and max spare threads, current thread count and current thread busy. Request information : Max processing time and processing time, request and error count, bytes received and sent. A table showing Stage, Time, Bytes Sent, Bytes Receive, Client, VHost and Request. All existing threads are listed in the table. Here is the list of the possible thread stages : "Parse and Prepare Request" : The request headers are being parsed or the necessary preparation to read the request body (if a transfer encoding has been specified) is taking place. "Service" : The thread is processing a request and generating the response. This stage follows the "Parse and Prepare Request" stage and precedes the "Finishing" stage. There is always at least one thread in this stage (the server-status page). "Finishing" : The end of the request processing. Any remainder of the response still in the output buffers is sent to the client. This stage is followed by "Keep-Alive" if it is appropriate to keep the connection alive or "Ready" if "Keep-Alive" is not appropriate. "Keep-Alive" : The thread keeps the connection open to the client in case the client sends another request. If another request is recieved, the next stage will br "Parse and Prepare Requst". If no request is received before the keep alive times out, the connection will be closed and the next stage will be "Ready". "Ready" : The thread is at rest and ready to be used.

Executing Manager Commands With Ant

In addition to the ability to execute Manager commands via HTTP requests, as documented above, Tomcat 5 includes a convenient set of Task definitions for the Ant (version 1.4 or later) build tool. In order to use these commands, you must perform the following setup operations: Download the binary distribution of Ant from http://ant.apache.org. You must use version 1.4 or later. Install the Ant distribution in a convenient directory (called ANT_HOME in the remainder of these instructions). Copy the file server/lib/catalina-ant.jar from your Tomcat 5 installation into Ant's library directory ($ANT_HOME/lib). Add the $ANT_HOME/bin directory to your PATH environment variable. Configure at least one username/password combination in your Tomcat user database that includes the manager role. To use custom tasks within Ant, you must declare them first with a  element. Therefore, your build.xml file might look something like this: Now, you can execute commands like ant deploy to deploy the application to a running instance of Tomcat, or ant reload to tell Tomcat to reload it. Note also that most of the interesting values in this build.xml file are defined as replaceable properties, so you can override their values from the command line. For example, you might consider it a security risk to include the real manager password in your build.xml file's source code. To avoid this, omit the password property, and specify it from the command line: ant -Dpassword=secret deploy Tasks output capture Using Ant version 1.6.2 or later, the Catalina tasks offer the option to capture their output in properties or external files. They support directly the following subset of the  type attributes: Attribute Description Required output Name of a file to which to write the output. If the error stream is not also redirected to a file or property, it will appear in this output. No error The file to which the standard error of the command should be redirected. No logError This attribute is used when you wish to see error output in Ant's log and you are redirecting output to a file/property. The error output will not be included in the output file/property. If you redirect error with theerror or errorProperty attributes, this will have no effect. No append Whether output and error files should be appended to or overwritten. Defaults to false. No createemptyfiles Whether output and error files should be created even when empty. Defaults to true. No outputproperty The name of a property in which the output of the command should be stored. Unless the error stream is redirected to a separate file or stream, this property will include the error output. No errorproperty The name of a property in which the standard error of the command should be stored. No A couple of additional attributes can also be specified: Attribute Description Required alwaysLog This attribute is used when you wish to see the output you are capturing, appearing also in the Ant's log. It must not be used unless you are capturing task output. Defaults to false. This attribute will be supported directly by  in Ant 1.6.3 No failonerror This attribute is used when you wish to avoid that any manager command processing error terminates the ant execution. Defaults to true. It must be set to false, if you want to capture error output, otherwise execution will terminate before anything can be captured.  This attribute acts only on manager command execution, any wrong or missing command attribute will still cause Ant execution termination. No They also support the embedded  element in which you can specify its full set of attributes, but input, inputstringand inputencoding that, even if accepted, are not used because they have no meaning in this context. Refer to ant manual for details on  element attributes. Here is a sample build file extract that shows how this output redirection support can be used: WARNING: even if it doesn't make many sense, and is always a bad idea, calling a Catalina task more than once, badly set Ant tasks depends chains may cause that a task be called more than once in the same Ant run, even if not intended to. A bit of caution should be exercised when you are capturing output from that task, because this could lead to something unexpected: when capturing in a property you will find in it only the output from the first call, because Ant properties are immutable and once set they cannot be changed, when capturing in a file, each run will overwrite it and you will find in it only the last call output, unless you are using theappend="true" attribute, in which case you will see the output of each task call appended to the file.

Using the JMX Proxy Servlet

What is JMX Proxy Servlet The JMX Proxy Servlet is a lightweight proxy to get and set the tomcat internals. (Or any class that has been exposed via an MBean) Its usage is not very user friendly but the UI is extremely help for integrating command line scripts for monitoring and changing the internals of tomcat. You can do two things with the proxy: get information and set information. For you to really understand the JMX Proxy Servlet, you should have a general understanding of JMX. If you don't know what JMX is, then prepare to be confused. JMX Query command This takes the form: http://webserver/manager/jmxproxy/?qry=STUFF Where  STUFF is the JMX query you wish to perform. For example, here are some queries you might wish to run: qry=*%3Atype%3DRequestProcessor%2C* --> type=RequestProcessor which will locate all workers which can process requests and report their state. qry=*%3Aj2eeType=Servlet%2c* --> j2eeType=Servlet which return all loaded servlets. qry=Catalina%3Atype%3DEnvironment%2Cresourcetype%3DGlobal%2Cname%3DsimpleValue --> Catalina:type=Environment,resourcetype=Global,name=simpleValue which look for a specific MBean by the given name. You'll need to experiment with this to really understand its capabilites. If you provide no  qry parameter, then all of the MBeans will be displayed. We really recommend looking at the tomcat source code and understand the JMX spec to get a better understanding of all the queries you may run. JMX Set command Now that you can query an MBean, its time to muck with Tomcat's internals! The general form of the set command is : http://webserver/manager/jmxproxy/?set=BEANNAME&att=MYATTRIBUTE&val=NEWVALUE So you need to provide 3 request parameters: set: The full bean name att: The attribute you wish to alter val: The new value If all goes ok, then it will say OK, otherwise an error message will be shown. For example, lets say we wish to turn up debugging on the fly for the  ErrorReportValve. The following will set debugging to 10. http://localhost:8080/manager/jmxproxy/ ?set=Catalina%3Atype%3DValve%2Cname%3DErrorReportValve%2Chost%3Dlocalhost&att=debug&val=10 and my result is (YMMV): Result: ok Here is what I see if I pass in a bad value. Here is the URL I used, I try set debugging equal to 'cowbell': http://localhost:8080/manager/jmxproxy/ ?set=Catalina%3Atype%3DValve%2Cname%3DErrorReportValve%2Chost%3Dlocalhost&att=debug&val=cowbell When I try that, my result is Error: java.lang.NumberFormatException: For input string: "cowbell"