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How to configure Servlet in XML

Source: Internet
Author: User
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In Web applications, we can use xml to configure Servlet and provide initialization parameters for them, as shown in the following example:

The Servlet we created is: ServletDemo. java. The Code is as follows:

 
 
    
  
  
  1. /*  
    2. 
  
  
  2. *Createdon2005-8-29  
    3. 
  
  
  3. *  
    4. 
  
  
  4. *TODOTochangethetemplateforthisgeneratedfilegoto  
    5. 
  
  
  5. *Window-Preferences-Java-CodeStyle-CodeTemplates  
    6. 
  
  
  6. */  
    7. 
  
  
  7. packagezy.pro.wd.servlet;  
    8. 
  
  
  8. importjava.io.IOException;  
    9. 
  
  
  9. importjava.io.PrintWriter;  
    10. 
  
  
  10. importjavax.sql.DataSource;  
    11. 
  
  
  11. importjavax.servlet.ServletException;  
    12. 
  
  
  12. importjavax.servlet.http.HttpServlet;  
    13. 
  
  
  13. importjavax.servlet.http.HttpServletRequest;  
    14. 
  
  
  14. importjavax.servlet.http.HttpServletResponse;  
    15. 
  
  
  15. /**//**  
    16. 
  
  
  16. *@authorzhangyi  
    17. 
  
  
  17. *  
    18. 
  
  
  18. *TODOTochangethetemplateforthisgeneratedtypecommentgoto  
    19. 
  
  
  19. *Window-Preferences-Java-CodeStyle-CodeTemplates  
    20. 
  
  
  20. */  
    21. 
  
  
  21. publicclassServletDemoextendsHttpServlet...{  
    22. 
  
  
  22. Stringmessage;  
    23. 
  
  
  23. DataSourceds;  
    24. 
  
  
  24. /**//**  
    25. 
  
  
  25. *Constructoroftheobject.  
    26. 
  
  
  26. */  
    27. 
  
  
  27. publicServletDemo()...{  
    28. 
  
  
  28. super();  
    29. 
  
  
  29. }  
    30. 
  
  
  30. /**//**  
    31. 
  
  
  31. *Destructionoftheservlet.<br> 
    32. 
  
  
  32. */  
    33. 
  
  
  33. publicvoiddestroy()...{  
    34. 
  
  
  34. super.destroy();//Justputs"destroy"stringinlog  
    35. 
  
  
  35. //Putyourcodehere  
    36. 
  
  
  36. }  
    37. 
  
  
  37. /**//**  
    38. 
  
  
  38. *ThedoGetmethodoftheservlet.<br> 
    39. 
  
  
  39. *  
    40. 
  
  
  40. *Thismethodiscalledwhenaformhasitstagvaluemethodequalstoget.  
    41. 
  
  
  41. *  
    42. 
  
  
  42. *@paramrequesttherequestsendbytheclienttotheserver  
    43. 
  
  
  43. *@paramresponsetheresponsesendbytheservertotheclient  
    44. 
  
  
  44. *@throwsServletExceptionifanerroroccurred  
    45. 
  
  
  45. *@throwsIOExceptionifanerroroccurred  
    46. 
  
  
  46. */  
    47. 
  
  
  47. publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)  
    48. 
  
  
  48. throwsServletException,IOException...{  
    49. 
  
  
  49. response.setContentType("text/html");  
    50. 
  
  
  50. PrintWriterout=response.getWriter();  
    51. 
  
  
  51. out.println("<!DOCTYPEHTMLPUBLIC\"-//W3C//DTDHTML4.01Transitional//EN\">");  
    52. 
  
  
  52. out.println("<HTML>");  
    53. 
  
  
  53. out.println("<HEAD><TITLE>AServlet</TITLE></HEAD>");  
    54. 
  
  
  54. out.println("<BODY>");  
    55. 
  
  
  55. out.print("Thisis");  
    56. 
  
  
  56. out.print(this.getClass());  
    57. 
  
  
  57. out.println(",usingtheGETmethod<br>");  
    58. 
  
  
  58. out.println(this.getServletConfig().getInitParameter("message"));  
    59. 
  
  
  59. out.println("</BODY>");  
    60. 
  
  
  60. out.println("</HTML>");  
    61. 
  
  
  61. out.flush();  
    62. 
  
  
  62. out.close();  
    63. 
  
  
  63. }  
    64. 
  
  
  64. /**//**  
    65. 
  
  
  65. *ThedoPostmethodoftheservlet.<br> 
    66. 
  
  
  66. *  
    67. 
  
  
  67. *Thismethodiscalledwhenaformhasitstagvaluemethodequalstopost.  
    68. 
  
  
  68. *  
    69. 
  
  
  69. *@paramrequesttherequestsendbytheclienttotheserver  
    70. 
  
  
  70. *@paramresponsetheresponsesendbytheservertotheclient  
    71. 
  
  
  71. *@throwsServletExceptionifanerroroccurred  
    72. 
  
  
  72. *@throwsIOExceptionifanerroroccurred  
    73. 
  
  
  73. */  
    74. 
  
  
  74. publicvoidinit()throwsServletException...{  
    75. 
  
  
  75. //Putyourcodehere  
    76. 
  
  
  76. }  
    77. 
  
  
  77. } 
    78.

In this Servlet, we define two attributes: message and ds. We now make the following configuration in web. xml:

 
 
    
  
  
  1. <servlet> 
    2. 
  
  
  2. <description> 
    3. 
  
  
  3. ThisisthedescriptionofmyJ2EEcomponent  
    4. 
  
  
  4. </description> 
    5. 
  
  
  5. <display-name> 
    6. 
  
  
  6. ThisisthedisplaynameofmyJ2EEcomponent  
    7. 
  
  
  7. </display-name> 
    8. 
  
  
  8. <servlet-name>ServletDemo</servlet-name> 
    9. 
  
  
  9. <servlet-class>zy.pro.wd.servlet.ServletDemo</servlet-class> 
    10. 
  
  
  10. <init-param> 
    11. 
  
  
  11. <description>initializethefieldofmessage</description> 
    12. 
  
  
  12. <param-name>message</param-name> 
    13. 
  
  
  13. <param-value> 
    14. 
  
  
  14. welcomehere,thankyouforvisiting!!!  
    15. 
  
  
  15. </param-value> 
    16. 
  
  
  16. </init-param> 
    17. 
  
  
  17. </servlet> 
    18. 
  
  
  18. <servlet-mapping> 
    19. 
  
  
  19. <servlet-name>ServletDemo</servlet-name> 
    20. 
  
  
  20. <url-pattern>/servlet/ServletDemo</url-pattern> 
    21. 
  
  
  21. </servlet-mapping> 
    22.

The bold part is the configuration we want to make. Here, we set the initial value for the message attribute:
Welcomehere, thankyouforvisiting !!!

Note: we cannot set the initial value for ds at the same time, because the DTD of web. xml stipulates that only one attribute can be defined, that is, only one parameter value pair can be declared in the configuration file. In this way, we can access this attribute in our servlet as follows: this. getServletConfig (). getInitParameter ("message "). However, sometimes we need to use XML to initialize multiple attributes at the same time, so we need to write the XML file and parse it ourselves.

Advantages of configuring Servlet using XML:
If you do not configure Servlet in XML, You need to restart the server if you modify the Servlet attributes. If you use XML for configuration, you do not need to restart the server and it will take effect automatically. The server can automatically monitor its changes and reload the documents. For enterprises, the continuous operation of the system is very important.

XML to configure Servlet is mainly used when the initialization parameters need to be changed during running.

  1. Servlet Engine installation
  2. Configure the Servlet Development Environment
  3. JSP Servlet call in tag Library
  4. Small issues encountered when learning Java Servlet
  5. Servlet sharing links in sessions

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

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