tomcat中的一个过滤器例证

tomcat中的一个过滤器例子

感谢：http://www.iteye.com/wiki/Struts/578-Struts原理与实践（5）?和Google

将所有的request的字符集也设置为UTF-8。虽然，我们可以在每个文件中加入这样的句子：request.setCharacterEncoding("UTF-8");来解决，但这样显得很麻烦。一种更简单的解决方法是使用filter。具体步骤如下：?

在mystruts\WEB-INF\classes目录下再新建一个名为filters的目录，新建一个名为：SetCharacterEncodingFilter的类，并保存在该目录下。其实，这个类并不要您亲自来写，可以借用tomcat中的例子。现将该例子的程序节选如下：?

1. package?filters; ??
2. import?java.io.IOException; ??
3. import?javax.servlet.Filter; ??
4. import?javax.servlet.FilterChain; ??
5. import?javax.servlet.FilterConfig; ??
6. import?javax.servlet.ServletException; ??
7. import?javax.servlet.ServletRequest; ??
8. import?javax.servlet.ServletResponse; ??
9. import?javax.servlet.UnavailableException; ??
10. ?
11. public?class?SetCharacterEncodingFilter?implements?Filter?{ ??
12. ??
13. ??

14.  //可以理解为默认编码，在web.xml中配置后读取存入

15. ????protected?String?encoding?=?null; ??
16. ??
17. 
    
18. ????protected?FilterConfig?filterConfig?=?null; ??
19. 
    
20. ????protected?boolean?ignore?=?true; ??
21. ??
22. ????public?void?destroy()?{ ??
23. ??
24. ????????this.encoding?=?null; ??
25. ????????this.filterConfig?=?null; ??
26. ??
27. ????} ??
28. ??
29. ??
30. ????public?void?doFilter(ServletRequest?request,?ServletResponse?response, ??
31. ?????????????????????????FilterChain?chain) ??
32. ????????throws?IOException,?ServletException?{ ??
33. ??
34. ????????//?Conditionally?select?and?set?the?character?encoding?to?be?used?
35. //如果被忽略或者请求未设置编码，为了防止乱码，进行编码过滤??
36. ????????if?(ignore?||?(request.getCharacterEncoding()?==?null))?{ ??

37. //设置请求编码为web.xml中配置的编码类型

38. ????????????String?encoding?=?selectEncoding(request); ??
39. ????????????if?(encoding?!=?null) ??
40. ????????????????request.setCharacterEncoding(encoding); ??
41. ????????} ??
42. ??
43. ????????//?Pass?control?on?to?the?next?filter?
44. //由FilterChain进行过滤处理，而不是该Filter??
45. ????????chain.doFilter(request,?response); ??
46. ??
47. ????} ??
48. ??

49.  //主要从配置文件中读取配置项并进行赋值

50. ????public?void?init(FilterConfig?filterConfig)?throws?ServletException?{ ??
51. ??
52. ????????this.filterConfig?=?filterConfig; ??

53.   //从web.xml读取配置的编码，如gbk，utf－8等，赋值给encoding

54. ????????this.encoding?=?filterConfig.getInitParameter("encoding");??

55.   //从web.xml读取是否忽略

56. ????????String?value?=?filterConfig.getInitParameter("ignore");??
57. ????????if?(value?==?null)??
58. ????????????this.ignore?=?true;??
59. ????????else?if?(value.equalsIgnoreCase("true"))??
60. ????????????this.ignore?=?true;??
61. ????????else?if?(value.equalsIgnoreCase("yes")) ??
62. ????????????this.ignore?=?true; ??
63. ????????else??
64. ????????????this.ignore?=?false; ??
65. ??
66. ????} ??

1. ?protected?String?selectEncoding(ServletRequest?request)?{ ??
2. ??
3. ????????return?(this.encoding); ??
4. ??
5. ????} ??
6. ??
7. }?

1. <filter>??
2. ????<filter-name>Set?Character?Encoding</filter-name>??
3. ????<filter-class>filters.SetCharacterEncodingFilter</filter-class>??
4. ????<init-param>??
5. ??????<param-name>encoding</param-name>??
6. ??????<param-value>UTF-8</param-value>??
7. ????</init-param>??
8. ??</filter>??
9. ??<filter-mapping>??
10. ????<filter-name>Set?Character?Encoding</filter-name>??
11. ????<url-pattern>/*</url-pattern>??
12. </filter-mapping>??