{"id":1488,"date":"2012-09-25T15:33:03","date_gmt":"2012-09-25T07:33:03","guid":{"rendered":"http:\/\/rmohan.com\/?p=1488"},"modified":"2012-09-25T15:53:58","modified_gmt":"2012-09-25T07:53:58","slug":"apache-tomcat-7","status":"publish","type":"post","link":"https:\/\/mohan.sg\/?p=1488","title":{"rendered":"Apache Tomcat 7"},"content":{"rendered":"
TABLE OF CONTENTS (HIDE)<\/a><\/h5>\n

1.\u00a0\u00a0Introduction<\/a>
1.1\u00a0\u00a0Web Application (Webapp)<\/a>
1.2\u00a0\u00a0Hypertext Transfer Protocol (HTTP)<\/a>
1.3\u00a0\u00a0Apache Tomcat HTTP Server<\/a>
2.\u00a0\u00a0How to Install Tomcat 7 and Get Started with Java Servlet Programming<\/a>
2.1\u00a0\u00a0STEP 0: Read the Tomcat Documentation<\/a>
2.2\u00a0\u00a0STEP 1: Download and Install Tomcat<\/a>
2.3\u00a0\u00a0STEP 2: Create an Environment Variable JAVA_HOME<\/a>
2.4\u00a0\u00a0STEP 3: Configure Tomcat Server<\/a>
2.5\u00a0\u00a0STEP 4: Start Tomcat Server<\/a>
2.6\u00a0\u00a0STEP 5: Develop and Deploy a WebApp<\/a>
2.7\u00a0\u00a0STEP 6: Write a “Hello-world” Java Servlet<\/a>
2.8\u00a0\u00a0STEP 7: Write a Database Servlet<\/a>
2.9\u00a0\u00a0(Advanced) Deploying Servlet using @WebServlet (Servlet 3.0 on Tomcat 7)<\/a>
3.\u00a0\u00a0How to Debug?<\/a><\/p>\n

 <\/p>\n

 <\/p>\n

This tutorial can be completed in a 3-hour session, with guidance from instructor.<\/p>\n

This installation and configuration guide is applicable to Tomcat 7, and possibly the earlier versions.<\/p>\n

(EE3072 Students) This guide is applicable to “IM3072”, but NOT applicable to “EE3072”. For EE3072, please read “Tomcat 6 – How to Install and Configure<\/a>“.<\/p>\n

1.\u00a0\u00a0Introduction<\/h3>\n

1.1\u00a0\u00a0Web Application (Webapp)<\/h4>\n

A web application<\/em> (or webapp), unlike standalone application, runs over the Internet. Examples of web applications are google, amazon, ebay, facebook and twitter. A webapp is typically a 3-tier<\/em> (or multi-tier<\/em>) client-server application<\/em>, typically involving a database<\/em>.<\/p>\n

Most of the webapps run on the HTTP application protocol, with browser as the client to access an HTTP server.<\/p>\n

A web database application requires five components, as illustrated below:<\/p>\n

    \n
  1. HTTP Server: E.g., Apache HTTP Server, Apache Tomcat HTTP Server, Microsoft IIS, and etc.<\/li>\n
  2. HTTP Client (or Web Browser): E.g., MSIE, FireFox, Chrome, and etc.<\/li>\n
  3. Database: E.g., MySQL, Oracle, DB2, Infomix, MS SQL Server, MS Access, and etc.<\/li>\n
  4. Client-Side Programs: could be written in HTML Form, JavaScript, VBScript, Flash, and etc.<\/li>\n
  5. Server-Side Programs: could be written in Java Servlet\/JSP, ASP, PHP, and etc.<\/li>\n<\/ol>\n

    \"\"<\/a><\/p>\n

     <\/p>\n

    A user, via a web browser, issue a URL to an HTTP server to start a webapp. The webapp first downloads a client-side program (such as an HTML form) into the browser. The user fills up the query criteria in the form. The client-side program sends the query parameters to a server-side program, which queries the database and returns the query result to the client. The client-side program displays the result on the browser.<\/p>\n

    1.2\u00a0\u00a0Hypertext Transfer Protocol (HTTP)<\/h4>\n

    HTTP is an asynchronous request-response application-layer protocol<\/em>. A client sends a request message to the server. The server returns a response message to the client. The syntax of the message is defined in the HTTP specification.<\/p>\n

    \"\"<\/a><\/p>\n

    .3\u00a0\u00a0Apache Tomcat HTTP Server<\/h4>\n

    Apache Tomcat<\/em> is a Java-capable HTTP server, which could execute special Java programs known as Java Servlet and Java Server Pages (JSP). It is the official Reference Implementation<\/em> (RI<\/em>) for Java Servlets and JavaServer Pages (JSP) technologies. Tomcat is an open-source<\/em> project, under the “Apache Software Foundation” (which also provides the famous open-source industrial-strength Apache HTTP Server). The mother site for Tomcat is http:\/\/tomcat.apache.org<\/a>. Alternatively, you can find tomcat via the Apache mother site @ http:\/\/www.apache.org<\/a>.<\/p>\n

    2.\u00a0\u00a0How to Install Tomcat 7 and Get Started with Java Servlet Programming<\/h3>\n

    2.1\u00a0\u00a0STEP 0: Read the Tomcat Documentation<\/h4>\n

    Tomcat’s documentation is available at Tomcat mother site @ http:\/\/tomcat.apache.org<\/a>. Select “Documentation” ? “Tomcat 7.0”.<\/p>\n

    2.2\u00a0\u00a0STEP 1: Download and Install Tomcat<\/h4>\n
      \n
    1. From http:\/\/tomcat.apache.org<\/a> ? Select “Downloads” ? “Tomcat 7.0” ? “7.0.xx” (where xx is the latest upgrade number) ? “Binary Distributions” ? “Core” ? “zip” ? “apache-tomcat-7.0.xx.zip<\/code>“.<\/li>\n
    2. UNZIP into a directory of your choice. DO NOT unzip onto the Desktop (because its path is hard to locate). I suggest using “d:\\myproject<\/code>“. Tomcat will be unzipped into directory “d:\\myproject\\apache-tomcat-7.0.xx<\/code>“. For ease of use, we shall shorten and rename this directory to “d:\\myproject\\tomcat<\/code>“. Take note of Your Tomcat Installed Directory<\/strong>. Hereafter, I shall refer to the Tomcat installed directory as <TOMCAT_HOME><\/code>.<\/li>\n<\/ol>\n

      I recommend “zip” version, as you could simply delete the entire directory when Tomcat is no longer needed (without running any un-installer). You are free to move or rename the Tomcat’s installed directory. You can install (unzip) multiple copies of Tomcat in the same machine.<\/p>\n

      \n

      (For Mac Users) Read “How to Install Tomcat 7 on Mac<\/a>” Step 1.<\/p>\n<\/div>\n

      2.3\u00a0\u00a0STEP 2: Create an Environment Variable JAVA_HOME<\/h4>\n

      You need to create an environment variable<\/em> called “JAVA_HOME<\/code>” and set it to your JDK installed directory.<\/p>\n

        \n
      1. First, take note of your JDK installed directory (the default is “c:\\program files\\java\\jdk1.7.0<\/code>_xx”).<\/li>\n
      2. Start a CMD shell, and issue the command “SET JAVA_HOME<\/code>” to check if variable JAVA_HOME<\/code>is set:\n
        prompt> set JAVA_HOME<\/strong>\r\nEnvironment variable JAVA_HOME not defined<\/pre>\n
        If JAVA_HOME<\/code> is set (by other applications), check if it is set to your JDK installed directory.<\/p>\n<\/li>\n
      3. To set\/change an environment variable in Windows 2000\/XP\/Vista\/7: Click “Start” button ? “Control Panel” ? “System” ? (Vista\/7) “Advanced system settings” ? Switch to “Advanced” tab ? “Environment Variables” ? “System Variables” (or “User Variables” for the current user only) ? “New” (or “Edit” for modification) ? In “Variable Name” field, enter “JAVA_HOME<\/code>” ? In “Variable Value” field, enter your JDK installed directory (e.g., “c:\\program file\\java\\jdk1.7.0<\/code>“) – I suggest that you copy and paste the directory name to avoid typo error!<\/li>\n
      4. To verify, RE-START<\/strong>a CMD shell and issue:\n
        prompt> set JAVA_HOME<\/strong>\r\nJAVA_HOME=c:\\program file\\java\\jdk1.7.0   <== CHECK! YOUR JDK installed directory<\/pre>\n<\/li>\n<\/ol>\n
        \n
        (For Mac Users) Take note of your JDK installed directory (most likely under \/usr\/local<\/code>). Start a Terminal and run:<\/p>\n
        $ echo $JAVA_HOME                       \/\/ Check if JAVA_HOME is already set\r\n\r\n\/\/ If JAVA_HOME is not set, then\r\n$ java_home=your_jdk_install_directory<\/em>  \/\/ Set environment variable java_home\r\n$ export java_home                      \/\/ Make this variable available to all applications<\/pre>\n
        To make permanent changes, store the above command in “.bash_profile<\/code>” in your home directory (denoted as '~'<\/code>), and run “source $HOME\/.bash_profile<\/code>” to refresh.<\/p>\n<\/div>\n
        2.4\u00a0\u00a0STEP 3: Configure Tomcat Server<\/h4>\n
        (Note) Programmers need to view the file extension<\/em> (such as .txt<\/code>, .ini<\/code>). To display the file extension in Windows, run “Control Panel” ? “Folder Options” ? Select tab “View” ? Uncheck “Hide extensions for known file types”.<\/p>\n
        The Tomcat configuration files are located in the “conf<\/code>” sub-directory of your Tomcat installed directory (e.g. “d:\\myproject\\tomcat\\conf<\/code>“). There are 3 configuration files:<\/p>\n
          \n
        1. server.xml<\/code><\/li>\n
        2. web.xml<\/code><\/li>\n
        3. context.xml<\/code><\/li>\n<\/ol>\n
          Make a backup of the configuration files before you proceed.<\/p>\n
          Step 3(a) “server.xml” – Set the TCP Port Number<\/strong><\/h5>\n
          Use a text editor (e.g., NotePad++, TextPad or NotePad) to open the configuration file “server.xml<\/code>“, under the “conf<\/code>” sub-directory of Tomcat installed directory (e.g. “d:\\myproject\\tomcat\\conf<\/code>“).<\/p>\n
          The default TCP port number configured in Tomcat is 8080, you may choose any number between 1024 and 65535, which is not used by an existing application. We shall use port 9999 in this article. (For production server, you should use port 80, which is pre-assigned to HTTP server as the default port number.)<\/p>\n
          <!-- Define a non-SSL HTTP\/1.1 Connector<\/strong> on port 8080 -->\r\n<Connector port=\"9999\"<\/strong> protocol=\"HTTP\/1.1<\/strong>\" connectionTimeout=\"20000\" redirectPort=\"8443\" \/><\/pre>\n
          Step 3(b) “web.xml” – Enabling Directory Listing<\/strong><\/h5>\n
          Again, use a text editor to open the configuration file “web.xml<\/code>“, under the “conf<\/code>” sub-directory of Tomcat installed directory.<\/p>\n
          We shall enable directory listing by changing “listings<\/code>” from “false<\/code>” to “true<\/code>” for the “default<\/code>” servlet, as shown in red.<\/p>\n
          <!-- The default servlet for all web applications, that serves static     -->\r\n<!-- resources.  It processes all requests that are not mapped to other   -->\r\n<!-- servlets with servlet mappings.                                      -->\r\n<servlet>\r\n  <servlet-name>default<\/strong><\/servlet-name>\r\n  <servlet-class>org.apache.catalina.servlets.DefaultServlet<\/servlet-class>\r\n  <init-param>\r\n    <param-name>debug<\/param-name>\r\n    <param-value>0<\/param-value>\r\n  <\/init-param>\r\n  <init-param>\r\n    <param-name>listings<\/strong><\/param-name>\r\n    <param-value>true<\/strong><\/param-value>\r\n  <\/init-param>\r\n  <load-on-startup>1<\/load-on-startup>\r\n<\/servlet><\/pre>\n
          Step 3(c) “context.xml” – Enabling Automatic Reload<\/strong><\/h5>\n
          Again, use a text editor to open the configuration file “context.xml<\/code>“, under the “conf<\/code>” sub-directory of Tomcat installed directory.<\/p>\n
          We shall add the attribute reloadable=\"true\"<\/code> to the <Context><\/code> element to enable automatic reload after code changes, as shown in red.<\/p>\n
          <Context reloadable=\"true\"<\/strong>>\r\n   ......\r\n<\/Context><\/pre>\n
          2.5\u00a0\u00a0STEP 4: Start Tomcat Server<\/h4>\n
          The Tomcat’s executable programs are kept in the “bin<\/code>” sub-directory of the Tomcat installed directory (e.g., “d:\\myproject\\tomcat\\bin<\/code>“).<\/p>\n
          Step 4(a) Start Server<\/h5>\n
          Launch a CMD shell. Set the current directory to “<TOMCAT_HOME<\/code>>\\bin<\/code>“, and run “startup.bat<\/code>” as follows:<\/p>\n
          \/\/ Change the current directory to Tomcat's \"bin\"\r\n\/\/ Assume that Tomcat is installed in \"d:\\myproject\\tomcat\"\r\nprompt> d:<\/strong>                     \/\/ Change the current drive\r\nD:\\...> cd \\<\/strong>                   \/\/ Change Directory to ROOT directory\r\nD:\\> cd \\myproject\\tomcat\\bin<\/strong>  \/\/ Change Directory to YOUR Tomcat's \"bin\" directory\r\n \r\n\/\/ Start Tomcat Server\r\nD:\\myproject\\tomcat\\bin> startup<\/strong><\/pre>\n
          A new Tomcat console window appears. Study the messages on the console. Look out for the Tomcat’s port number (double check that Tomcat is running on port 9999). Future error messages will be send to this console. System.out.println()<\/code> issued by your Java servlets will also be sent to this console.<\/p>\n
          ......\r\nINFO: Initializing Coyote HTTP\/1.1 on http-9999<\/strong>\r\n......\r\nINFO: Starting Coyote HTTP\/1.1 on http-9999<\/strong>\r\n......\r\nINFO: Server startup in 699 ms<\/pre>\n
          \n
          (For Mac Users) Read “How to Install Tomcat 7 on Mac<\/a>” Step 2.<\/p>\n<\/div>\n
          Step 4(b) Start a Client to Access the Server<\/h5>\n
          Start a browser (as a HTTP client), and issue URL “http:\/\/localhost:9999<\/code>” to access the Tomcat server’s welcome page. The hostname “localhost<\/code>” (with IP address of 127.0.0.1<\/code>) is meant for local loop-back testing. For users on the other machines over the net, they have to use the server’s IP address or DNS domain name or hostname in the format of “http:\/\/serverHostnameOrIPAddress<\/em>:9999<\/code>“.<\/p>\n
           <\/p>\n
          \"\"<\/a><\/p>\n
           <\/p>\n
          Step 4(c) Shutdown Server<\/h5>\n
          You can shutdown the server by running “<TOMCAT_HOME>\\bin\\shutdown.bat<\/strong><\/code>“. If Tomcat does not respond to the shutdown command, you could terminate Tomcat by pushing control-c<\/em> (or control-break<\/em>) on the Tomcat’s console. DO NOT kill the cat by pushing the “close” button.<\/p>\n
          (Skip Unless …) Cannot Start Tomcat<\/h5>\n