常用Servlet过滤器用例

编程语言 2018-12-31 09:40:51 阅读次数: 0

解决POST请求参数中文和输出中文的乱码过滤器

过滤器代码

package com.study.java.filter;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
 * @Name: SetCharacterEncodingFilter
 * @Description: 过滤器应用案例一：解决POST请求参数中文和输出中文的乱码过滤器
 */
public class SetCharacterEncodingFilter implements Filter {
    private FilterConfig filterConfig;

    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
    }

    public void doFilter(ServletRequest request, ServletResponse response, 
                         FilterChain chain) throws IOException, ServletException {
        //拦截客户端请求 //设置客户端请求参数内容编码，针对post请求
        String encode = filterConfig.getInitParameter("encode");
        if(encode == null || "".equals(encode.toString().trim())) { encode = "UTF-8" ; }
        request.setCharacterEncoding(encode) ; 
        //设置服务端响应内容编码
        response.setContentType("text/html;charset=" + encode) ;
        //放行，让目标资源执行
        chain.doFilter(request, response) ;
    }

    public void destroy() {
        
    }

}

 web.xml配置

<!-- 解决POST请求参数中文和输出中文的乱码 -->
<filter>
    <filter-name>SetCharacterEncodingFilter</filter-name>
    <filter-class>com.study.java.filter.SetCharacterEncodingFilter</filter-class> <!-- 设置客户端请求参数编码 -->
    <init-param>
        <param-name>encode</param-name>
        <param-value>UTF-8</param-value>
    </init-param>
</filter> 
<!-- 过滤器执行顺序以此标签定义的顺序为准 --> 
<filter-mapping>
<filter-name>SetCharacterEncodingFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

控制动态资源不要在客户端缓存过滤器

过滤器代码

package com.study.java.filter;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * @Name: DynamicResourceNoCacheFilter
 * @Description: 过滤器应用案例二：控制动态资源不要在客户端缓存
 * @Version: V1.0
 */
public class DynamicResourceNoCacheFilter implements Filter {
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        //拦截客户端请求
        // 对请求与响应对象进行类型转换，参考HttpServlet的service()方法实现
        HttpServletRequest request;
        HttpServletResponse response;
        try {
            request = (HttpServletRequest)req;
            response = (HttpServletResponse)res;
        } catch(ClassCastException e) {
            throw new ServletException("non-HTTP request or response");
        }
        //设置http响应头信息：禁止浏览器缓存
        response.setHeader("expires", "-1");
        response.setHeader("cache-control", "no-cache");
        response.setHeader("pragma", "no-cache");
        //放行，让目标资源执行
        chain.doFilter(request, response);
    }
    public void destroy() {

    } 

}

web.xml配置 

<!-- 控制动态资源不要在客户端缓存 -->
<filter>
    <filter-name>DynamicResourceNoCacheFilter</filter-name>
    <filter-class>com.study.java.filter.DynamicResourceNoCacheFilter</filter-class>
</filter> 
<filter-mapping>
<filter-name>DynamicResourceNoCacheFilter</filter-name>
<url-pattern>*.jsp</url-pattern>
</filter-mapping> 
<filter-mapping>
<filter-name>DynamicResourceNoCacheFilter</filter-name>
<url-pattern>/servlet/*</url-pattern>
</filter-mapping>

控制静态资源的缓存时间过滤器

过滤器代码

package com.study.java.filter;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * @Name: SetStaticResourceCacheTime
 * @Description: 过滤器应用案例三：控制静态资源的缓存时间
 * @Version: V1.0
 */
public class SetStaticResourceCacheTime implements Filter {
    private FilterConfig filterconfig;

    public void init(FilterConfig filterconfig) throws ServletException {
        this.filterconfig = filterconfig;
    }

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterchain) throws IOException, ServletException { 
        //拦截客户端请求 
        //对请求与响应对象进行类型转换，参考HttpServlet的service()方法实现 
        HttpServletRequest request; 
        HttpServletResponse response; 
        try { 
            request = (HttpServletRequest)req; 
            response = (HttpServletResponse)res; 
        } catch(ClassCastException e) { 
            throw new ServletException("non-HTTP request or response"); 
        } 
        //缓存时间：毫秒为单位 
        long time = 0 ; 
        //获取用户的访问资源类型 
        String uri = request.getRequestURI() ; 
        //截取扩展名 
        String subname = uri.substring(uri.lastIndexOf(".") + 1);
        //说明访问的是html资源 
        if("html".equals(subname)) { 
            String value = filterconfig.getInitParameter(subname); 
            time = Long.parseLong(value) * 60 * 60 * 1000; 
        } //说明访问的是css资源
        if("css".equals(subname)) { 
            String value = filterconfig.getInitParameter(subname); 
            time = Long.parseLong(value) * 60 * 60 * 1000; 
        } 
        //说明访问的是js资源 
        if("js".equals(subname)) { 
            String value = filterconfig.getInitParameter(subname); 
            time = Long.parseLong(value) * 60 * 60 * 1000; 
        } 
        //设置缓存过期时间 
        response.setDateHeader("Expires", System.currentTimeMillis() + time); 
        //放行，让目标资源执行 
        filterchain.doFilter(request, response); 
    } 
    
    public void destroy() {
        
    } 
    
}

web.xml配置

<!-- 控制静态资源的缓存时间 -->
<filter>
    <filter-name>SetStaticResourceCacheTime</filter-name>
    <filter-class>com.study.java.filter.SetStaticResourceCacheTime</filter-class>
    <init-param>
        <param-name>html</param-name> <!-- 单位：小时 -->
        <param-value>1</param-value>
    </init-param>
    <init-param>
        <param-name>js</param-name> <!-- 单位：小时 -->
        <param-value>2</param-value>
    </init-param>
    <init-param>
        <param-name>css</param-name> <!-- 单位：小时 -->
        <param-value>3</param-value>
    </init-param>
</filter> 

<filter-mapping>
<filter-name>SetStaticResourceCacheTime</filter-name>
<url-pattern>*.html</url-pattern>
</filter-mapping> 
<filter-mapping>
<filter-name>SetStaticResourceCacheTime</filter-name>
<url-pattern>*.css</url-pattern>
</filter-mapping> 
<filter-mapping>
<filter-name>SetStaticResourceCacheTime</filter-name>
<url-pattern>*.js</url-pattern>
</filter-mapping>

控制用户资源访问权限过滤器

过滤器代码

package com.study.java.filter;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * @Name: ResourceAuthorityFilter
 * @Description: 过滤器应用案例四：控制用户资源访问权限
 * @Version: V1.0
 */
public class ResourceAuthorityFilter implements Filter {
    public void init(FilterConfig filterconfig) throws ServletException {
    }

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterchain) throws IOException, ServletException {
        //拦截客户端请求
        // 对请求与响应对象进行类型转换，参考HttpServlet的service()方法实现
        HttpServletRequest request;
        HttpServletResponse response;
        try {
            request = (HttpServletRequest)req;
            response = (HttpServletResponse)res;
        } catch(ClassCastException e) {
            throw new ServletException("non-HTTP request or response");
        }
        //获取请求uri地址
        String uri = request.getRequestURI() ;
        应用名+资源访问路径 String resourcePath = uri.substring(request.getContextPath().length()) ;
        //资源访问路径
        // 判断admin级别网页的浏览权限
        if(uri.startsWith("/admin")) {
            if(request.getSession().getAttribute("admin")==null) {
                request.setAttribute("message","您没有这个权限");
                request.getRequestDispatcher("/login.jsp").forward(request,response);
                return;
            }
        }
        //判断manage级别网页的浏览权限
        if(uri.startsWith("/manage")) {
            //这里省去
        }
        //下面还可以添加其他的用户权限，省去。
    }
    public void destroy() {

    }

}

web.xml配置

<!-- 控制用户资源访问权限过滤器 -->
<filter>
    <filter-name>ResourceAuthorityFilter</filter-name>
    <filter-class>com.study.java.filter.ResourceAuthorityFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>ResourceAuthorityFilter</filter-name>
<url-pattern>/admin/*</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>ResourceAuthorityFilter</filter-name>
<url-pattern>/manage/*</url-pattern>
</filter-mapping>

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