Table Of Contents<\/h3>\n\n- 1. Introduction<\/a><\/dt>\n
- \n
\n- 1.1 Servlet Process<\/a><\/dt>\n
- 1.2 Merits<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 2. Lifecycle<\/a><\/dt>\n
- 3. Container<\/a><\/dt>\n
- \n
\n- 3.1 Services<\/a><\/dt>\n
- 3.2 Servlet Container Configurations<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 4. Demo: To start with<\/a><\/dt>\n
- 5. Filter<\/a><\/dt>\n
- \n
\n- 5.1 Interface<\/a><\/dt>\n
- 5.2 Example<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 6. Session<\/a><\/dt>\n
- \n
\n- 6.1 Session Handling<\/a><\/dt>\n
- 6.2 Mechanism of Session Handling<\/a><\/dt>\n
- 6.3 Example<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 7. Exception Handling<\/a><\/dt>\n
- \n
\n- 7.1 Error Code Configuration<\/a><\/dt>\n
- 7.2 Exception- Type Configuration<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 8. Debugging<\/a><\/dt>\n
- \n
\n- 8.1 Message Logging<\/a><\/dt>\n
- 8.2 Java Debugger<\/a><\/dt>\n
- 8.3 Headers<\/a><\/dt>\n
- 8.4 Refresh<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 9. Internationalization<\/a><\/dt>\n
- \n
\n- 9.1 Methods<\/a><\/dt>\n
- 9.2 Example<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 10. References<\/a><\/dt>\n
- \n
\n- 10.1 Website<\/a><\/dt>\n
- 10.2 Book<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 11. Conclusion<\/a><\/dt>\n
- 12. Download<\/a><\/dt>\n<\/dl>\n<\/div>\n
<\/a>1. Introduction<\/h2>\nServlet is a Java programming language class, part of Java Enterprise Edition (Java EE). Sun Microsystems developed its first version 1.0 in the year 1997. Its current Version is Servlet 3.1.<\/p>\n
Servlets are used for creating dynamic web applications in java by extending the capability of a server. It can run on any web server integrated with a Servlet container.<\/p>\n
<\/a>1.1 Java Servlet Process<\/h3>\nThe process of a servlet is shown below:<\/p>\n
![\"Java](\"http:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2014\/12\/servlet-processing-of-user-requests.jpg\")
<\/a>Figure 1: servlet processing of user requests<\/figcaption><\/figure><\/p>\n\n- A Request is sent by a client to a servlet container. The container acts as a Web server.<\/li>\n
- The Web server searches for the servlet and initiates it.<\/li>\n
- The client request is processed by the servlet and it sends the response back to the server.<\/li>\n
- The Server response is then forwarded to the client.<\/li>\n<\/ul>\n
<\/a>1.2 Merits<\/h3>\n\n- Servlets are platform independent as they can run on any platform.<\/li>\n
- The Servlet API inherits all the features of the Java platform.<\/li>\n
- It builds and modifies the security logic for server-side extensions.<\/li>\n
- Servlets inherit the security provided by the Web Server.<\/li>\n
- In Servlet, only a single instance of the requests runs concurrently. It does not run in a separate process. So, it saves the memory by removing the overhead of creating a new process for each request.<\/li>\n<\/ul>\n
<\/a>2. Life Cycle<\/h2>\nServlet lifecycle describes how the servlet container manages the servlet object.<\/p>\n
\n- Load Servlet Class<\/li>\n
- Servlet Instance is created by the web container when the servlet class is loaded<\/li>\n
init()<\/code>:This is called only once when the servlet is created. There is no need to call it again and again for multiple requests.<\/li>\n<\/ul>\n public void init() throws ServletException {\n\n }<\/pre>\n\nservice()<\/code>: It is called by the web container to handle request from clients. Here the actual functioning of the code is done. The web container calls this method each time when request for the servlet is received.<\/li>\n<\/ul>\nIt calls doGet()<\/code>, doPost()<\/code>, doTrace()<\/code>, doPut()<\/code>, doDelete()<\/code> and other methods<\/p>\n\ndoGet()<\/code>:<\/li>\n<\/ul>\npublic void doGet(HttpServletRequest request,HttpServletResponse response)\n throws ServletException, IOException {\n\/\/ code\n}<\/pre>\n\ndoPost()<\/code>:<\/li>\n<\/ul>\npublic void doPost(HttpServletRequest request, HttpServletResponse response)\n throws ServletException, IOException {\n \/\/ code\n}<\/pre>\n\ndestroy()<\/code>: It is used to clean resources and called before removing the servlet instance.<\/li>\n<\/ul>\npublic void destroy()<\/pre>\n![\"Java](\"http:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2014\/12\/Servlet-Life-Cycle.jpg\")
<\/a>Figure 2: Servlet Life Cycle<\/figcaption><\/figure><\/p>\n<\/a>3. Container<\/h2>\nIt is known as servlet engine which manages Java Servlet components on top of a web server to the request send by the client.<\/p>\n
<\/a>3.1 Services<\/h3>\nServlet Container provides the following services:<\/p>\n
\n- It manages the servlet life cycle.<\/li>\n
- The resources like servlets, JSP pages and HTML files are managed by servlet container.<\/li>\n
- It appends session ID to the URL path to maintain session.<\/li>\n
- Provides security service.<\/li>\n
- It loads a servlet class from network services, file systems like remote file system and local file system.<\/li>\n<\/ul>\n
<\/a>3.2 Servlet Container Configurations<\/h3>\nThe servlet container can be configured with the web server to manage servlets in three ways listed below:<\/p>\n
\n- Standalone container<\/li>\n
- In-process container<\/li>\n
- Out-process container<\/li>\n<\/ul>\n
Standalone container<\/strong>: In this type the Web Server functionality is taken by the Servlet container. Here, the container is strongly coupled with the Web server.<\/p>\nIn-Process container<\/strong>: In this the container runs within the Web server process.<\/p>\nOut-Process container<\/strong>: In this type there is a need to configure the servlet container to run outside the Web server process. It is used in some cases like if there is a need to run Servlets and Servlet container in different process\/systems.<\/p>\n<\/a>4. Demo: To start with<\/h2>\nHere is an example showing Demo Servlet. Follow these steps to start with your first Servlet Application in NetBeansIDE.<\/p>\n
Step 1:<\/strong> Open NetBeansIDE -> File -> New Project->WebApplication -><\/em> Set Project name as WebApplicationServletDemo<\/em><\/p>\n![\"Java](\"http:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2014\/12\/Figure3.jpg\")
<\/a>Figure 3: Create new WebApplication project in NetBeansIDE: WebApplicationServletDemo<\/figcaption><\/figure><\/p>\nStep 2:<\/strong> Now click on Next ><\/em>as shown above. This will create new project with the following directory structure.<\/p>\n![\"Java](\"http:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2014\/12\/Figure4.jpg\")
<\/a>Figure 4: Project Directory after creating new project<\/figcaption><\/figure><\/p>\nStep 3:<\/strong> Create new servlet application by Right Clicking on Project Directory-> New -> Servlet<\/em><\/p>\n![\"Java](\"http:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2014\/12\/Figure5.jpg\")
<\/a>Figure 5: Adding Servlet file<\/figcaption><\/figure><\/p>\nStep 4:<\/strong> Add the Servlet Class Name as \u201cServletDemo<\/em>\u201d and click on Next<\/em>.<\/p>\n![\"Java](\"http:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2014\/12\/Figure6.jpg\")
<\/a>Figure 6: Adding Servlet Class Name<\/figcaption><\/figure><\/p>\nStep 5: <\/strong>Now, Configure Servlet Deployment by checking \u201cAdd information to deployment descriptor (web.xml)<\/em>” and adding URL Pattern (the link visible) as ServletDemo<\/em>. This step will generate web.xml<\/em> file in WEB-INF<\/em> folder.<\/p>\n![\"Java](\"http:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2014\/12\/Figure7.jpg\")
<\/a>Figure 7: Configuring Servlet Deployment<\/figcaption><\/figure><\/p>\nStep 6:<\/strong> Click on Finish as shown above, this will add ServletDemo.java servlet under project directory. Check the changes under Directory Structure:<\/p>\n![\"Java](\"http:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2014\/12\/Figure8.jpg\")
<\/a>Figure 8: Changes under project directory after configuring<\/figcaption><\/figure><\/p>\nHere is the code for deployment descriptor (web.xml) with URL-patter as \/ServletDemo<\/em>:<\/p>\nListing 1: web.xml<\/span><\/p>\n<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<web-app version=\"3.1\" xmlns=\"http:\/\/xmlns.jcp.org\/xml\/ns\/javaee\" xmlns:xsi=\"http:\/\/www.w3.org\/2001\/XMLSchema-instance\" xsi:schemaLocation=\"http:\/\/xmlns.jcp.org\/xml\/ns\/javaee http:\/\/xmlns.jcp.org\/xml\/ns\/javaee\/web-app_3_1.xsd\">\n<servlet>\n<servlet-name>ServletDemo<\/servlet-name>\n<servlet-class>ServletDemo<\/servlet-class>\n<\/servlet>\n<servlet-mapping>\n <servlet-name>ServletDemo<\/servlet-name>\n <url-pattern>\/ServletDemo<\/url-pattern>\n<\/servlet-mapping>\n<session-config>\n<session-timeout>\n 30\n<\/session-timeout>\n<\/session-config>\n<\/web-app><\/pre>\nHere,<\/p>\n
<servlet-name>: name given to Servlet\n<servlet-class>: servlet class\n<servlet-mapping>: maps internal name to URL\n<url-pattern>: link displays when Servlet runs<\/pre>\nThe hyperlink Next<\/em> is mentioned as ServletDemo<\/em>. So, when the user will click on it, the page will redirect to ServletDemo<\/em> servlet whose url-pattern is mentioned as ServetDemo<\/em>:<\/p>\nListing 2: index.html<\/span><\/p>\n<html>\n<head>\n<title>Welcome<\/title>\n<meta charset=\"UTF-8\">\n<meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">\n<\/head>\n<body>\n<div><h2>Welcome<\/h2><\/div>\n<p>We're still under development stage. Stay Tuned for our website's new design and learning content.<\/p>\n<a href=\"ServletDemo\"><b>Next<\/b><\/a>\n<\/body>\n<\/html><\/pre>\nListing 3: ServletDemo.java<\/span><\/p>\nimport java.io.IOException;\nimport java.io.PrintWriter;\nimport javax.servlet.ServletException;\nimport javax.servlet.http.HttpServlet;\nimport javax.servlet.http.HttpServletRequest;\nimport javax.servlet.http.HttpServletResponse;\n\npublic class ServletDemo extends HttpServlet {\n\n\tprotected void processRequest(HttpServletRequest request, HttpServletResponse response)\n\t\t\tthrows ServletException, IOException {\n\t\tresponse.setContentType(\"text\/html;charset=UTF-8\");\n\t\ttry (PrintWriter out = response.getWriter()) {\n\t\t\tout.println(\"<!DOCTYPE html>\");\n\t\t\tout.println(\"<html>\");\n\t\t\tout.println(\"<head>\");\n\t\t\tout.println(\"<title>Servlet ServletDemo<\/title>\"); \n\t\t\tout.println(\"<\/head>\");\n\t\t\tout.println(\"<body>\");\n\t\t\tout.println(\"<h1>Servlet ServletDemo at \" + request.getContextPath() + \"<\/h1>\");\n\t\t\tout.println(\"<\/body>\");\n\t\t\tout.println(\"<\/html>\");\n\t\t}\n\t}\n\n\t@Override\n\tprotected void doGet(HttpServletRequest request, HttpServletResponse response)\n\t\t\tthrows ServletException, IOException {\n\t\tresponse.setContentType(\"text\/html;charset=UTF-8\");\n\t\tPrintWriter out = response.getWriter(); \n\t\ttry {\n\t\t\t\/* TODO output your page here. You may use following sample code. *\/ \n\t\t\tout.println(\"<!DOCTYPE html>\"); \n\t\t\tout.println(\"<html>\");\n\t\t\tout.println(\"<head>\");\n\t\t\tout.println(\"<title>Servlets<\/title>\");\n\t\t\tout.println(\"<\/head>\");\n\t\t\tout.println(\"<body>\");\n\t\t\tout.println(\"<br \/><p><h2>First Demo Servlet application<\/h2><br \/>Here, the URL-pattern is ServletDemo in web.xml. So, the address is <i>WebApplicationServletDemo\/ServletDemo<\/i>.<\/p>\");\n\t\t\tout.println(\"<br \/><br \/><a href=\\\"index.html\\\">Previous Page<\/a>\");\n\t\t\tout.println(\"<\/body>\");\n\t\t\tout.println(\"<\/html>\");\n\t\t} \n\t\tfinally \n\t\t{ \n\t\tout.close(); \n\t\t}\n\t}\n}\n<\/pre>\n![\"Java](\"http:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2014\/12\/Figure9.jpg\")
<\/a>Figure 9: Output showing index.html welcome page<\/figcaption><\/figure>
\n![\"Java](\"http:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2014\/12\/Figure10.jpg\")
<\/a>Figure 10: Output showing redirection to ServletDemo.java<\/figcaption><\/figure> <\/div> <\/div><\/p>\n<\/a>5. Filter<\/h2>\nFilters transform the content of requests, responses, and header information from one format to another. These are reusable codes.<\/p>\n
\n- Filter class is declared in the deployment descriptor.<\/li>\n
- It is used to write reusable components.<\/li>\n
- The request is process before it is called using filters.<\/li>\n
- It can be used under a web application for some tasks like:\n
\n- Validation<\/li>\n
- Compression<\/li>\n
- Verification<\/li>\n
- Internationalization<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
<\/a>5.1 Interface<\/h3>\nIt consists of these 3 filters:<\/p>\n
- \n
- 1.1 Servlet Process<\/a><\/dt>\n
- 1.2 Merits<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 2. Lifecycle<\/a><\/dt>\n
- 3. Container<\/a><\/dt>\n
- \n
- \n
- 3.1 Services<\/a><\/dt>\n
- 3.2 Servlet Container Configurations<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 4. Demo: To start with<\/a><\/dt>\n
- 5. Filter<\/a><\/dt>\n
- \n
- \n
- 5.1 Interface<\/a><\/dt>\n
- 5.2 Example<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 6. Session<\/a><\/dt>\n
- \n
- \n
- 6.1 Session Handling<\/a><\/dt>\n
- 6.2 Mechanism of Session Handling<\/a><\/dt>\n
- 6.3 Example<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 7. Exception Handling<\/a><\/dt>\n
- \n
- \n
- 7.1 Error Code Configuration<\/a><\/dt>\n
- 7.2 Exception- Type Configuration<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 8. Debugging<\/a><\/dt>\n
- \n
- \n
- 8.1 Message Logging<\/a><\/dt>\n
- 8.2 Java Debugger<\/a><\/dt>\n
- 8.3 Headers<\/a><\/dt>\n
- 8.4 Refresh<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 9. Internationalization<\/a><\/dt>\n
- \n
- \n
- 9.1 Methods<\/a><\/dt>\n
- 9.2 Example<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 10. References<\/a><\/dt>\n
- \n
- \n
- 10.1 Website<\/a><\/dt>\n
- 10.2 Book<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 11. Conclusion<\/a><\/dt>\n
- 12. Download<\/a><\/dt>\n<\/dl>\n<\/div>\n
<\/a>1. Introduction<\/h2>\n
Servlet is a Java programming language class, part of Java Enterprise Edition (Java EE). Sun Microsystems developed its first version 1.0 in the year 1997. Its current Version is Servlet 3.1.<\/p>\n
Servlets are used for creating dynamic web applications in java by extending the capability of a server. It can run on any web server integrated with a Servlet container.<\/p>\n
<\/a>1.1 Java Servlet Process<\/h3>\n
The process of a servlet is shown below:<\/p>\n
<\/a>Figure 1: servlet processing of user requests<\/figcaption><\/figure><\/p>\n - \n
- A Request is sent by a client to a servlet container. The container acts as a Web server.<\/li>\n
- The Web server searches for the servlet and initiates it.<\/li>\n
- The client request is processed by the servlet and it sends the response back to the server.<\/li>\n
- The Server response is then forwarded to the client.<\/li>\n<\/ul>\n
<\/a>1.2 Merits<\/h3>\n
- \n
- Servlets are platform independent as they can run on any platform.<\/li>\n
- The Servlet API inherits all the features of the Java platform.<\/li>\n
- It builds and modifies the security logic for server-side extensions.<\/li>\n
- Servlets inherit the security provided by the Web Server.<\/li>\n
- In Servlet, only a single instance of the requests runs concurrently. It does not run in a separate process. So, it saves the memory by removing the overhead of creating a new process for each request.<\/li>\n<\/ul>\n
<\/a>2. Life Cycle<\/h2>\n
Servlet lifecycle describes how the servlet container manages the servlet object.<\/p>\n
- \n
- Load Servlet Class<\/li>\n
- Servlet Instance is created by the web container when the servlet class is loaded<\/li>\n
init()<\/code>:This is called only once when the servlet is created. There is no need to call it again and again for multiple requests.<\/li>\n<\/ul>\npublic void init() throws ServletException {\n\n }<\/pre>\n- \n
service()<\/code>: It is called by the web container to handle request from clients. Here the actual functioning of the code is done. The web container calls this method each time when request for the servlet is received.<\/li>\n<\/ul>\nIt calls
doGet()<\/code>,doPost()<\/code>,doTrace()<\/code>,doPut()<\/code>,doDelete()<\/code> and other methods<\/p>\n- \n
doGet()<\/code>:<\/li>\n<\/ul>\npublic void doGet(HttpServletRequest request,HttpServletResponse response)\n throws ServletException, IOException {\n\/\/ code\n}<\/pre>\n- \n
doPost()<\/code>:<\/li>\n<\/ul>\npublic void doPost(HttpServletRequest request, HttpServletResponse response)\n throws ServletException, IOException {\n \/\/ code\n}<\/pre>\n- \n
destroy()<\/code>: It is used to clean resources and called before removing the servlet instance.<\/li>\n<\/ul>\npublic void destroy()<\/pre>\n
<\/a>Figure 2: Servlet Life Cycle<\/figcaption><\/figure><\/p>\n <\/a>3. Container<\/h2>\n
It is known as servlet engine which manages Java Servlet components on top of a web server to the request send by the client.<\/p>\n
<\/a>3.1 Services<\/h3>\n
Servlet Container provides the following services:<\/p>\n
- \n
- It manages the servlet life cycle.<\/li>\n
- The resources like servlets, JSP pages and HTML files are managed by servlet container.<\/li>\n
- It appends session ID to the URL path to maintain session.<\/li>\n
- Provides security service.<\/li>\n
- It loads a servlet class from network services, file systems like remote file system and local file system.<\/li>\n<\/ul>\n
<\/a>3.2 Servlet Container Configurations<\/h3>\n
The servlet container can be configured with the web server to manage servlets in three ways listed below:<\/p>\n
- \n
- Standalone container<\/li>\n
- In-process container<\/li>\n
- Out-process container<\/li>\n<\/ul>\n
Standalone container<\/strong>: In this type the Web Server functionality is taken by the Servlet container. Here, the container is strongly coupled with the Web server.<\/p>\n
In-Process container<\/strong>: In this the container runs within the Web server process.<\/p>\n
Out-Process container<\/strong>: In this type there is a need to configure the servlet container to run outside the Web server process. It is used in some cases like if there is a need to run Servlets and Servlet container in different process\/systems.<\/p>\n
<\/a>4. Demo: To start with<\/h2>\n
Here is an example showing Demo Servlet. Follow these steps to start with your first Servlet Application in NetBeansIDE.<\/p>\n
Step 1:<\/strong> Open NetBeansIDE -> File -> New Project->WebApplication -><\/em> Set Project name as WebApplicationServletDemo<\/em><\/p>\n
<\/a>Figure 3: Create new WebApplication project in NetBeansIDE: WebApplicationServletDemo<\/figcaption><\/figure><\/p>\n Step 2:<\/strong> Now click on Next ><\/em>as shown above. This will create new project with the following directory structure.<\/p>\n
<\/a>Figure 4: Project Directory after creating new project<\/figcaption><\/figure><\/p>\n Step 3:<\/strong> Create new servlet application by Right Clicking on Project Directory-> New -> Servlet<\/em><\/p>\n
<\/a>Figure 5: Adding Servlet file<\/figcaption><\/figure><\/p>\n Step 4:<\/strong> Add the Servlet Class Name as \u201cServletDemo<\/em>\u201d and click on Next<\/em>.<\/p>\n
<\/a>Figure 6: Adding Servlet Class Name<\/figcaption><\/figure><\/p>\n Step 5: <\/strong>Now, Configure Servlet Deployment by checking \u201cAdd information to deployment descriptor (web.xml)<\/em>” and adding URL Pattern (the link visible) as ServletDemo<\/em>. This step will generate web.xml<\/em> file in WEB-INF<\/em> folder.<\/p>\n
<\/a>Figure 7: Configuring Servlet Deployment<\/figcaption><\/figure><\/p>\n Step 6:<\/strong> Click on Finish as shown above, this will add ServletDemo.java servlet under project directory. Check the changes under Directory Structure:<\/p>\n
<\/a>Figure 8: Changes under project directory after configuring<\/figcaption><\/figure><\/p>\n Here is the code for deployment descriptor (web.xml) with URL-patter as \/ServletDemo<\/em>:<\/p>\n
Listing 1: web.xml<\/span><\/p>\n
<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<web-app version=\"3.1\" xmlns=\"http:\/\/xmlns.jcp.org\/xml\/ns\/javaee\" xmlns:xsi=\"http:\/\/www.w3.org\/2001\/XMLSchema-instance\" xsi:schemaLocation=\"http:\/\/xmlns.jcp.org\/xml\/ns\/javaee http:\/\/xmlns.jcp.org\/xml\/ns\/javaee\/web-app_3_1.xsd\">\n<servlet>\n<servlet-name>ServletDemo<\/servlet-name>\n<servlet-class>ServletDemo<\/servlet-class>\n<\/servlet>\n<servlet-mapping>\n <servlet-name>ServletDemo<\/servlet-name>\n <url-pattern>\/ServletDemo<\/url-pattern>\n<\/servlet-mapping>\n<session-config>\n<session-timeout>\n 30\n<\/session-timeout>\n<\/session-config>\n<\/web-app><\/pre>\n
Here,<\/p>\n
<servlet-name>: name given to Servlet\n<servlet-class>: servlet class\n<servlet-mapping>: maps internal name to URL\n<url-pattern>: link displays when Servlet runs<\/pre>\n
The hyperlink Next<\/em> is mentioned as ServletDemo<\/em>. So, when the user will click on it, the page will redirect to ServletDemo<\/em> servlet whose url-pattern is mentioned as ServetDemo<\/em>:<\/p>\n
Listing 2: index.html<\/span><\/p>\n
<html>\n<head>\n<title>Welcome<\/title>\n<meta charset=\"UTF-8\">\n<meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">\n<\/head>\n<body>\n<div><h2>Welcome<\/h2><\/div>\n<p>We're still under development stage. Stay Tuned for our website's new design and learning content.<\/p>\n<a href=\"ServletDemo\"><b>Next<\/b><\/a>\n<\/body>\n<\/html><\/pre>\n
Listing 3: ServletDemo.java<\/span><\/p>\n
import java.io.IOException;\nimport java.io.PrintWriter;\nimport javax.servlet.ServletException;\nimport javax.servlet.http.HttpServlet;\nimport javax.servlet.http.HttpServletRequest;\nimport javax.servlet.http.HttpServletResponse;\n\npublic class ServletDemo extends HttpServlet {\n\n\tprotected void processRequest(HttpServletRequest request, HttpServletResponse response)\n\t\t\tthrows ServletException, IOException {\n\t\tresponse.setContentType(\"text\/html;charset=UTF-8\");\n\t\ttry (PrintWriter out = response.getWriter()) {\n\t\t\tout.println(\"<!DOCTYPE html>\");\n\t\t\tout.println(\"<html>\");\n\t\t\tout.println(\"<head>\");\n\t\t\tout.println(\"<title>Servlet ServletDemo<\/title>\"); \n\t\t\tout.println(\"<\/head>\");\n\t\t\tout.println(\"<body>\");\n\t\t\tout.println(\"<h1>Servlet ServletDemo at \" + request.getContextPath() + \"<\/h1>\");\n\t\t\tout.println(\"<\/body>\");\n\t\t\tout.println(\"<\/html>\");\n\t\t}\n\t}\n\n\t@Override\n\tprotected void doGet(HttpServletRequest request, HttpServletResponse response)\n\t\t\tthrows ServletException, IOException {\n\t\tresponse.setContentType(\"text\/html;charset=UTF-8\");\n\t\tPrintWriter out = response.getWriter(); \n\t\ttry {\n\t\t\t\/* TODO output your page here. You may use following sample code. *\/ \n\t\t\tout.println(\"<!DOCTYPE html>\"); \n\t\t\tout.println(\"<html>\");\n\t\t\tout.println(\"<head>\");\n\t\t\tout.println(\"<title>Servlets<\/title>\");\n\t\t\tout.println(\"<\/head>\");\n\t\t\tout.println(\"<body>\");\n\t\t\tout.println(\"<br \/><p><h2>First Demo Servlet application<\/h2><br \/>Here, the URL-pattern is ServletDemo in web.xml. So, the address is <i>WebApplicationServletDemo\/ServletDemo<\/i>.<\/p>\");\n\t\t\tout.println(\"<br \/><br \/><a href=\\\"index.html\\\">Previous Page<\/a>\");\n\t\t\tout.println(\"<\/body>\");\n\t\t\tout.println(\"<\/html>\");\n\t\t} \n\t\tfinally \n\t\t{ \n\t\tout.close(); \n\t\t}\n\t}\n}\n<\/pre>\n<\/a>Figure 9: Output showing index.html welcome page<\/figcaption><\/figure>
\n<\/a>Figure 10: Output showing redirection to ServletDemo.java<\/figcaption><\/figure> <\/div> <\/div><\/p>\n<\/a>5. Filter<\/h2>\n
Filters transform the content of requests, responses, and header information from one format to another. These are reusable codes.<\/p>\n
- \n
- Filter class is declared in the deployment descriptor.<\/li>\n
- It is used to write reusable components.<\/li>\n
- The request is process before it is called using filters.<\/li>\n
- It can be used under a web application for some tasks like:\n
- \n
- Validation<\/li>\n
- Compression<\/li>\n
- Verification<\/li>\n
- Internationalization<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n
<\/a>5.1 Interface<\/h3>\n
It consists of these 3 filters:<\/p>\n
- 10.2 Book<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 9.2 Example<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 8.2 Java Debugger<\/a><\/dt>\n
- 7.2 Exception- Type Configuration<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 6.2 Mechanism of Session Handling<\/a><\/dt>\n
- 5.2 Example<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 3.2 Servlet Container Configurations<\/a><\/dt>\n<\/dl>\n<\/dd>\n
- 1.2 Merits<\/a><\/dt>\n<\/dl>\n<\/dd>\n
![\"Java](\"http:\/\/www.javacodegeeks.com\/wp-content\/uploads\/2014\/12\/Filter-API-Interfaces.jpg\")
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