Introduction

This is a process to read the value from web.xml file into the servlet. The servlet can get a value from its user without having an HTML form. The value of a parameter can be fetched from web.xml file by using getInitParameter() method of the servlet. The initial parameter can be defined in web.xml file by using the following tags given below as,
  1. <init-param>,<param-name>,<param-value>
  2. <servlet>
  3. <servlet-name>This contains a name to refer the servlet inside this file </servlet-name>
  4. <servlet-class>This contains class name of the servlet</servlet-class>
  5. <init-param>
  6. <param-name>This contains name of the initial parameter</param-name>
  7. <param-value> This contains value of the initial parameter </param-value>
  8. </init-param>
  9. </servlet>
Example
  1. //using initial parameter in a servlet
  3. import javax.servlet.*;
  4. import javax.servlet.http.*;
  5. import java.io.*;
  6. public class initParamServ extends HttpServlet
  7. {
  8. public void doGet(HttpServletRequest req,HttpServletResponse res)throws IOException,ServletException
  9. {
  10. String s1=getInitParameter("gp");
  11. res.setContentType("text/html");
  12. PrintWriter out=res.getWriter();
  13. out.println("<Html><body bgcolor='CYAN'>");
  14. out.println("<H1><font color='blue'>Today's Gold price<blink>"+s1+"</blink></font></h1>");
  15. out.println("</Body></html>");
  16. }
  17. }

Storing and Compiling

Store the file inside a class folder of the context (E:\Servlet\WEB-INF\classes).
Compile the file as below

javac -cp servlet-api.jar number.java (for tomcat 6.0)

complile Servlet
Setting in web.xml file
Note: - Note the Highlighted or bold portion in the below web.xml file, to be added.
  1. <?xml version="1.0" encoding="ISO-8859-1" ?> -
  2. <!--
  3. Licensed to the Apache Software Foundation (ASF) under one or more
  4. contributor license agreements. See the NOTICE file distributed with
  5. this work for additional information regarding copyright ownership.
  6. The ASF licenses this file to You under the Apache License, Version 2.0
  7. (the "License"); you may not use this file except in compliance with
  8. the License. You may obtain a copy of the License at
  10. http://www.apache.org/licenses/LICENSE-2.0
  12. Unless required by applicable law or agreed to in writing, software
  13. distributed under the License is distributed on an "AS IS" BASIS,
  14. WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15. See the License for the specific language governing permissions and
  16. limitations under the License.
  17. --> <!-- Inject Script Filtered -->
  18. <web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
  19. http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
  20. <servlet>
  21. <servlet-name>initParamServ</servlet-name>
  22. <servlet-class>initParamServ</servlet-class>
  23. <init-param>
  24. <param-name>gp</param-name>
  25. <param-value>21500</param-value>
  26. </init-param>
  27. </servlet>
  28. <servlet-mapping>
  29. <servlet-name>initParamServ</servlet-name>
  30. <url-pattern>/initParamServ</url-pattern>
  31. </servlet-mapping>
  32. </web-app>

Running it in a web browser

Please use the Mozilla Firefox browser to blink the value because Internet Explorer does not support <blink></blink> tag property.

First start the Apache Tomcat 6.0,
Here x is the context path location, which we have to give in the server.xml file, which is present inside the Tomcat installation directory (E:\Program Files\Apache Software Foundation\Tomcat 6.0\conf)

Server.xml settings
Note: - In the below server.xml file we have to specify the context path as below.
<Context path="/x" docBase="E:\Servlet" reloadable="true" debug="0" />

server.xml file
  1. <?xml version='1.0' encoding='utf-8'?>
  2. <!--
  3. Licensed to the Apache Software Foundation (ASF) under one or more
  4. contributor license agreements. See the NOTICE file distributed with
  5. this work for additional information regarding copyright ownership.
  6. The ASF licenses this file to You under the Apache License, Version 2.0
  7. (the "License"); you may not use this file except in compliance with
  8. the License. You may obtain a copy of the License at
  10. http://www.apache.org/licenses/LICENSE-2.0
  12. Unless required by applicable law or agreed to in writing, software
  13. distributed under the License is distributed on an "AS IS" BASIS,
  14. WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15. See the License for the specific language governing permissions and
  16. limitations under the License.
  17. -->
  18. <!-- Note: A "Server" is not itself a "Container", so you may not
  19. define subcomponents such as "Valves" at this level.
  20. Documentation at /docs/config/server.html
  21. -->
  22. <Server port="8005" shutdown="SHUTDOWN">
  24. <!--APR library loader. Documentation at /docs/apr.html -->
  25. <Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="on" />
  26. <!--Initialize Jasper prior to webapps are loaded. Documentation at /docs/jasper-howto.html -->
  27. <Listener className="org.apache.catalina.core.JasperListener" />
  28. <!-- JMX Support for the Tomcat server. Documentation at /docs/non-existent.html -->
  29. <Listener className="org.apache.catalina.mbeans.ServerLifecycleListener" />
  30. <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" />
  32. <!-- Global JNDI resources
  33. Documentation at /docs/jndi-resources-howto.html
  34. -->
  35. <GlobalNamingResources>
  36. <!-- Editable user database that can also be used by
  37. UserDatabaseRealm to authenticate users
  38. -->
  39. <Resource name="UserDatabase" auth="Container"
  40. type="org.apache.catalina.UserDatabase"
  41. description="User database that can be updated and saved"
  42. factory="org.apache.catalina.users.MemoryUserDatabaseFactory"
  43. pathname="conf/tomcat-users.xml" />
  44. </GlobalNamingResources>
  46. <!-- A "Service" is a collection of one or more "Connectors" that share
  47. a single "Container" Note: A "Service" is not itself a "Container",
  48. so you may not define subcomponents such as "Valves" at this level.
  49. Documentation at /docs/config/service.html
  50. -->
  51. <Service name="Catalina">
  53. <!--The connectors can use a shared executor, you can define one or more named thread pools-->
  54. <!--
  55. <Executor name="tomcatThreadPool" namePrefix="catalina-exec-"
  56. maxThreads="150" minSpareThreads="4"/>
  57. -->
  58. <!-- A "Connector" represents an endpoint by which requests are received
  59. and responses are returned. Documentation at :
  60. Java HTTP Connector: /docs/config/http.html (blocking & non-blocking)
  61. Java AJP Connector: /docs/config/ajp.html
  62. APR (HTTP/AJP) Connector: /docs/apr.html
  63. Define a non-SSL HTTP/1.1 Connector on port 8080
  64. -->
  65. <Connector port="8082" protocol="HTTP/1.1"
  66. connectionTimeout="20000"
  67. redirectPort="8443" />
  68. <!-- A "Connector" using the shared thread pool-->
  69. <!--
  70. <Connector executor="tomcatThreadPool"
  71. port="8080" protocol="HTTP/1.1"
  72. connectionTimeout="20000"
  73. redirectPort="8443" />
  74. -->
  75. <!-- Define a SSL HTTP/1.1 Connector on port 8443
  76. This connector uses the JSSE configuration, when using APR, the
  77. connector should be using the OpenSSL style configuration
  78. described in the APR documentation -->
  79. <!--
  80. <Connector port="8443" protocol="HTTP/1.1" SSLEnabled="true"
  81. maxThreads="150" scheme="https" secure="true"
  82. clientAuth="false" sslProtocol="TLS" />
  83. -->
  85. <!-- Define an AJP 1.3 Connector on port 8009 -->
  86. <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />
  87. <!-- An Engine represents the entry point (within Catalina) that processes
  88. every request. The Engine implementation for Tomcat stand alone
  89. analyzes the HTTP headers included with the request, and passes them
  90. on to the appropriate Host (virtual host).
  91. Documentation at /docs/config/engine.html -->
  93. <!-- You should set jvmRoute to support load-balancing via AJP ie :
  94. <Engine name="Standalone" defaultHost="localhost" jvmRoute="jvm1">
  95. -->
  96. <Engine name="Catalina" defaultHost="localhost">
  98. <!--For clustering, please take a look at documentation at:
  99. /docs/cluster-howto.html (simple how to)
  100. /docs/config/cluster.html (reference documentation) -->
  101. <!--
  102. <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster"/>
  103. -->
  105. <!-- The request dumper valve dumps useful debugging information about
  106. the request and response data received and sent by Tomcat.
  107. Documentation at: /docs/config/valve.html -->
  108. <!--
  109. <Valve className="org.apache.catalina.valves.RequestDumperValve"/>
  110. -->
  112. <!-- This Realm uses the UserDatabase configured in the global JNDI
  113. resources under the key "UserDatabase". Any edits
  114. that are performed against this UserDatabase are immediately
  115. available for use by the Realm. -->
  116. <Realm className="org.apache.catalina.realm.UserDatabaseRealm"
  117. resourceName="UserDatabase"/>
  119. <!-- Define the default virtual host
  120. Note: XML Schema validation will not work with Xerces 2.2.
  121. -->
  122. <Host name="localhost" appBase="webapps"
  123. unpackWARs="true" autoDeploy="true"
  124. xmlValidation="false" xmlNamespaceAware="false">
  126. <!-- SingleSignOn valve, share authentication between web applications
  127. Documentation at: /docs/config/valve.html -->
  128. <!--
  129. <Valve className="org.apache.catalina.authenticator.SingleSignOn" />
  130. -->
  132. <!-- Access log processes all example.
  133. Documentation at: /docs/config/valve.html -->
  134. <!--
  135. <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"
  136. prefix="localhost_access_log." suffix=".txt" pattern="common" resolveHosts="false"/>
  137. -->
  138. <Context path="/x" docBase="E:\Servlet" reloadable="true" debug="0" />
  139. </Host>
  140. </Engine>
  141. </Service>
  142. </Server>
Note: - In the below server.xml file we have to specify the context path as below.
Output
Servlet application
Thanks for reading and please be kind enough to give the feedback.