过滤源–过滤规则–过滤结果
过滤器是否能改变用户请求的web资源呢?也就是能否改变用户请求的路径?
可以
过滤器能否直接返回数据，能不能直接处理用户请求？
不能
多个过滤器详解
假如有两个过滤器，TestFilter、SecondFilter，他们的执行顺序如下：
start______doFilter_________TestFilter
start_________________doFilter____________SecondFilter
end_________________doFilter________________SecondFilter
end______doFilter_________TestFilter
Springmvc配置过滤器
编写TestFilter类
/**
* 过滤器测试
* Created by shirukai on 2017/10/31.
*/
public class TestFilter implements Filter {
private Logger logger = LoggerFactory.getLogger(this.getClass());
public void init(FilterConfig filterConfig) throws ServletException {
logger.info("__________________init________________TestFilter");
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
logger.info("start__________doFilter_________TestFilter");
chain.doFilter(request,response);//放行
logger.info("end__________doFilter_________TestFilter");
}
public void destroy() {
logger.info("__________________destroy________________TestFilter");
}
}
注册过滤器
在web.xml注册过滤器
<!--测试过滤器-->
<!-- <filter>
<filter-name>TestFilter</filter-name>
<filter-class>com.mavenssmlr.filter.TestFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>TestFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>-->
过滤器在实际项目中的应用场景
1. 对用户请求进行统一认证
编写LoginFilter类
/**
* 登录权限过滤器
* Created by shirukai on 2017/10/31.
*/
public class LoginFilter implements Filter {
private Logger logger = LoggerFactory.getLogger(this.getClass());
private FilterConfig config;
public void init(FilterConfig filterConfig) throws ServletException {
config = filterConfig;
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
HttpServletRequest httpServletRequest =(HttpServletRequest)request;
HttpServletResponse httpServletResponse = (HttpServletResponse) response;
//将cookie封装到map里
Map<String, Cookie> cookieMap = new HashMap<String, Cookie>();
Cookie[] cookies = httpServletRequest.getCookies();
if (null != cookies) {
for (Cookie cookie : cookies) {
cookieMap.put(cookie.getName(), cookie);
}
}
Cookie accessToken = cookieMap.get("accessToken");
//获取配置文件：不需要过滤的url
String[] noFilterUrls = config.getInitParameter("noFilterUrls").split(";");
for (int i = 0;i < noFilterUrls.length; i++){
if (httpServletRequest.getRequestURI().contains(noFilterUrls[i])){
chain.doFilter(request,response);
}
}
if (accessToken == null){
httpServletRequest.getRequestDispatcher("/user/login").forward(request,response);;
}
logger.info(httpServletRequest.getRequestURI());
String url = ((HttpServletRequest) request).getRequestURI();
chain.doFilter(request,response);
}
public void destroy() {
}
}
注册过滤器
<!--登录过滤器-->
<filter>
<filter-name>LoginFilter</filter-name>
<filter-class>com.mavenssmlr.filter.LoginFilter</filter-class>
<init-param>
<!--不需要过滤的url、静态资源-->
<param-name>noFilterUrls</param-name>
<param-value>/user/;/skins/</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>LoginFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
2. 编码转换
直接在web.xml配置即可
<!-- Spring字符编码过滤器配置，处理中文乱码，针对post请求 -->
<filter>
<filter-name>characterEncodingFilter</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>characterEncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
3.利用过滤器允许ajax跨域请求
编写过滤器类
/**
* 允许跨域请求过滤
* Created by shirukai on 2017/11/1.
*/
public class CORSFilter implements Filter {
public void init(FilterConfig filterConfig) throws ServletException {
}
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
HttpServletResponse response = (HttpServletResponse) servletResponse;
String origin = (String) servletRequest.getRemoteHost() + ":" + servletRequest.getRemotePort();
response.setHeader("Access-Control-Allow-Origin", "*");
response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS, DELETE");
response.setHeader("Access-Control-Max-Age", "3600");
response.setHeader("Access-Control-Allow-Headers", "x-requested-with,Authorization");
response.setHeader("Access-Control-Allow-Credentials", "true");
filterChain.doFilter(servletRequest, servletResponse);
}
public void destroy() {
}
}
注册过滤器
<!--允许跨域请求过滤-->
<filter>
<filter-name>CORSFilter</filter-name>
<filter-class>com.mavenssmlr.filter.CORSFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>CORSFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
参考地址：http://www.imooc.com/article/7719
