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SpringMVC 过滤器Filter使用解析
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SpringMVC框架是一个成熟的优秀java web开发框架，学习研究框架设计有助于我们更好的理解和掌握spring MVC，设计和写出更符合的结构和代码。
本节主要是研读SpringMVC框架中的过滤器设置，以编码处理过滤器为例来学习框架内是怎样设置过滤器的。
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" alt="" />
如上所示的spring-web.jar包结构所示， Spring的web包中中提供有很多过滤器，这些过滤器位于org.springframework.web.filter并且理所当然地实现了javax.servlet.Filter，
不过实现的方式有以下几类 ：
(1) 直接实现Filter，这一类过滤器只有CompositeFilter；
(2) 继承抽象类GenericFilterBean，该类实现了javax.servlet.Filter，这一类的过滤器只有一个，即DelegatingFilterProxy；
(3) 继承抽象类OncePerRequestFilter，该类为GenericFilterBean的直接子类，这一类过滤器包括CharacterEncodingFilter、HiddenHttpMethodFilter、HttpPutFormContentFilter、RequestContextFilter和ShallowEtagHeaderFilter；
(4) 继承抽象类AbstractRequestLoggingFilter，该类为OncePerRequestFilter的直接子类，这一类过滤器包括CommonsRequestLoggingFilter、Log4jNestedDiagnosticContextFilter和ServletContextRequestLoggingFilter。
过滤器放在容器结构的什么位置？
过滤器放在web资源之前，可以在请求抵达它所应用的web资源(可以是一个Servlet、一个Jsp页面，甚至是一个HTML页面)之前截获进入的请求，并且在它返回到客户之前截获输出请求。Filter：用来拦截请求，处于客户端与被请求资源之间，目的是重用代码。Filter链，在web.xml中哪个先配置，哪个就先调用。在filter中也可以配置一些初始化参数。
Java中的Filter 并不是一个标准的Servlet ，它不能处理用户请求，也不能对客户端生成响应。 主要用于对HttpServletRequest 进行预处理，也可以对HttpServletResponse 进行后处理，是个典型的处理链。
Filter 有如下几个种类：
l 用户授权的Filter: Filter 负责检查用户请求，根据请求过滤用户非法请求。
l 日志Filter: 详细记录某些特殊的用户请求。
l 负责解码的Filter: 包括对非标准编码的请求解码。
l 能改变XML 内容的XSLTFilter 等。
Filter 有如下几个用处 ：
l 在HttpServletRequest 到达Servlet 之前，拦截客户的HttpServletRequest 。
l 根据需要检查HttpServletRequest ，也可以修改HttpServletRequest 头和数据。
l 在HttpServletResponse 到达客户端之前，拦截HttpServletResponse 。
l 根据需要检查HttpServletResponse ，可以修改HttpServletResponse 头和数据。
创建一个
Filter
只需两个步骤
:
(1)创建Filter 处理类:
(2)在web.xml 文件中配置Filter 。
创建Filter 必须实现javax.servlet.Filter 接口，在该接口中定义了三个方法。
• void init(FilterConfig config): 用于完成Filter 的初始化。
• void destroy(): 用于Filter 销毁前，完成某些资源的回收。
• void doFilter(ServletRequest request, ServletResponse response,FilterChain
chain): 实现过滤功能，该方法就是对每个请求及响应增加的额外处理。
过滤器Filter也具有生命周期：init()->doFilter()->destroy()，由部署文件中的filter元素驱动。
参照编码过滤器示例来查看怎么实现的
- 首先配置在web.xml文件里的规则如下
<!-- 编码处理过滤器 -->
<filter>
<filter-name>encodingFilter</filter-name>
<filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>utf-8</param-value>
</init-param>
<init-param>
<param-name>forceEncoding</param-name>
<param-value>true</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>encodingFilter</filter-name>
<url-pattern>*.do</url-pattern>
</filter-mapping>
其中，filter-class 为过滤器Filter类，init-prama为注入的set参数
Filter-mapping中的url-pattern为过滤的url类型
类的继承关系
CharacterEncodingFilter r类继承了 OncePerRequestFilter 类
public class CharacterEncodingFilter extends OncePerRequestFilter
而 OncePerRequestFilter 类又继承了 GenericFilterBean 类
public abstract class OncePerRequestFilter extends GenericFilterBean
public abstract class GenericFilterBean implements
Filter, BeanNameAware, EnvironmentAware, ServletContextAware, InitializingBean, DisposableBean
设置编码的核心代码为
@Override
protected void doFilterInternal(
HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
throws ServletException, IOException {
if (this.encoding != null && (this.forceEncoding || request.getCharacterEncoding() == null)) {
request.setCharacterEncoding(this.encoding);
if (this.forceEncoding) {
response.setCharacterEncoding(this.encoding);
}
}
filterChain.doFilter(request, response);
}
其中filterChain为过滤器链，表示执行完这个过滤器之后接着执行下一个过滤器
区别
我们在使用过滤器时，通常没必要知道GenericFilterBean、OncePerRequestFilter和AbstractRequestLoggingFilter，但不防碍我们了解这几个类，就上文所述，AbstractRequestLoggingFilter继承自OncePerRequestFilter，OncePerRequestFilter继承自GenericFilterBean，所以我们知道，genericFilterBean是任何类型的过滤器的一个比较方便的超类，这个类主要实现的就是从web.xml文件中取得init-param中设定的值，然后对Filter进行初始化（当然，其子类可以覆盖init方法）。
OncePerRequestFilter继承自GenericFilterBean，那么它自然知道怎么去获取配置文件中的属性及其值，所以其重点不在于取值，而在于确保在接收到一个request后，每个filter只执行一次，它的子类只需要关注Filter的具体实现即doFilterInternal。
AbstractRequestLoggingFilter是对OncePerRequestFilter的扩展，它除了遗传了其父类及祖先类的所有功能外，还在doFilterInternal中决定了在过滤之前和之后执行的事件，它的子类关注的是beforeRequest和afterRequest。
总体来说，这三个类分别执行了Filter的某部分功能，当然，具体如何执行由它们的子类规定，若你需要实现自己的过滤器，也可以根据上文所述继承你所需要的类。
