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Java中filter用法完整代码示例

时间:2021-03-28 15:58     来源/作者:胡一生

本文研究的主要是Javafilter过滤器的相关用法,具体实现代码如下。

filter过滤器主要使用于前台向后台传递数据是的过滤操作。程度很简单就不说明了,直接给几个已经写好的代码:

一、使浏览器不缓存页面的过滤器

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import javax.servlet.*;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
 * 用于的使 Browser 不缓存页面的过滤器
 */
public class ForceNoCacheFilter implements Filter {
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException
  {
    ((HttpServletResponse) response).setHeader("Cache-Control","no-cache");
    ((HttpServletResponse) response).setHeader("Pragma","no-cache");
    ((HttpServletResponse) response).setDateHeader ("Expires", -1);
    filterChain.doFilter(request, response);
  }
  public void destroy()
  {
  }
  public void init(FilterConfig filterConfig) throws ServletException
  {
  }
}

二、检测用户是否登陆的过滤器

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public class CheckLoginFilter implements Filter  { 
  protected FilterConfig filterConfig = null
  private String redirectURL = null
  private List notCheckURLList = new ArrayList(); 
  private String sessionKey = null
 
  public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException 
  
    HttpServletRequest request = (HttpServletRequest) servletRequest; 
    HttpServletResponse response = (HttpServletResponse) servletResponse; 
 
    HttpSession session = request.getSession(); 
    if(sessionKey == null
    
      filterChain.doFilter(request, response); 
      return
    
    if((!checkRequestURIIntNotFilterList(request)) && session.getAttribute(sessionKey) == null
    
      response.sendRedirect(request.getContextPath() + redirectURL); 
      return
    
    filterChain.doFilter(servletRequest, servletResponse); 
  
 
  public void destroy() 
  
    notCheckURLList.clear(); 
  
 
  private boolean checkRequestURIIntNotFilterList(HttpServletRequest request) 
  
    String uri = request.getServletPath() + (request.getPathInfo() == null ? "" : request.getPathInfo()); 
    return notCheckURLList.contains(uri); 
  
 
  public void init(FilterConfig filterConfig) throws ServletException 
  
    this.filterConfig = filterConfig; 
    redirectURL = filterConfig.getInitParameter("redirectURL"); 
    sessionKey = filterConfig.getInitParameter("checkSessionKey"); 
 
    String notCheckURLListStr = filterConfig.getInitParameter("notCheckURLList"); 
 
    if(notCheckURLListStr != null
    
      StringTokenizer st = new StringTokenizer(notCheckURLListStr, ";"); 
      notCheckURLList.clear(); 
      while(st.hasMoreTokens()) 
      
        notCheckURLList.add(st.nextToken()); 
      
    
  
}

三、字符编码的过滤器

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import javax.servlet.*;
import java.io.IOException;
/**
 * 用于设置 HTTP 请求字符编码的过滤器,通过过滤器参数encoding指明使用何种字符编码,用于处理Html Form请求参数的中文问题
 */
public class CharacterEncodingFilter 
implements Filter 
{
    protected FilterConfig filterConfig = null;
    protected String encoding = "";
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException 
      {
        if(encoding != null
              servletRequest.setCharacterEncoding(encoding);
        filterChain.doFilter(servletRequest, servletResponse);
    }
    public void destroy() 
      {
        filterConfig = null;
        encoding = null;
    }
    public void init(FilterConfig filterConfig) throws ServletException 
      {
        this.filterConfig = filterConfig;
        this.encoding = filterConfig.getInitParameter("encoding");
    }
}

四、记录用户的访问操作器

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package com.qwserv.itm.pfl.log.svr;
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 java.text.SimpleDateFormat;
import javax.servlet.http.HttpServletRequest;
import com.qwserv.itm.api.pfl.sm.vo.Person;
import java.sql.*;
import com.qwserv.itm.api.ServiceAccess;
import com.qwserv.itm.util.toolkit.DebugUtil;
public class ObserveFilter implements Filter {
    protected static DebugUtil log = DebugUtil.getInstances("pfl-log", ObserveFilter.class);
    public void destroy() {
    }
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException,
      ServletException {
        //记录用户的访问操作
        HttpServletRequest request1 = (HttpServletRequest)request;
        StringBuffer url = request1.getRequestURL();
        //对url进行过滤,如果是js/css/image则不进行处理
        if (judgeFile(url.toString())){
            String operTime = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").
                      format(new java.util.Date());
            String hostIp = request.getRemoteAddr();
            String sessionId = request1.getRequestedSessionId();
            String userId = "";
            Person person = (Person)request1.getSession().getAttribute("userObj");
            if (null != person && null != person.getUser()){
                userId = person.getUser().getId();
            }
            String queryString = request1.getQueryString();
            if (null != queryString) {
                url.append('?');
                url.append(queryString);
            }
            //保存到数据库中
            saveToDb(userId,hostIp,sessionId,url.toString(),operTime,"");
        }
        // Pass control on to the next filter
        chain.doFilter(request, response);
    }
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    public Boolean judgeFile(String url){
        if (url.endsWith(".gif") || url.endsWith(".jpg") || url.endsWith(".png")
                || url.endsWith(".bmp") || url.endsWith(".css") || url.endsWith(".js")
                || url.endsWith(".jsx")){
            return false;
        } else {
            return true;
        }
    }
    public int saveToDb(String userId, String hostIp,String sessionId,String url,
          String operTime,String desc){
        //将报表任务数据保存到数据库中
        Connection conn = null;
        Statement st = null;
        try {
            //构造sql表达式,将数据插入数据库
            conn = ServiceAccess.getSystemSupportService().getDefaultConnection();
            st = conn.createStatement();
            String sql = "insert into LOG_OBSERVE_HISTORY(USERID,URL,Detail,SessionID,HostName,StartDate)  values('"+
                      userId + "','" + url + "','" + desc + "','" + sessionId
                      + "','" + hostIp + "','" + operTime + "')";
            if (ServiceAccess.getSystemSupportService().getConnectionType(conn)==ServiceAccess.getSystemSupportService().JCA_TYPE_ORACLE){
                sql = "insert into LOG_OBSERVE_HISTORY(Id,USERID,URL,Detail,SessionID,HostName,StartDate) values(LOG_OBSERVE_SEQ.nextval,'"+
                            userId + "','" + url + "','" + desc + "','" + sessionId
                            + "','" + hostIp + "',TO_DATE('" + operTime
                            + "','YYYY-MM-DD HH24:MI:SS'))";
            }
            st.executeUpdate(sql);
        }
        catch (Exception e) {
            e.printStackTrace();
            log.error("--------------------The url String is:" + url + "-------------------------------");
            return 1;
            //表示操作失败
        }
        finally {
            if (null != st)
                  {
                try{
                    st.close();
                }
                catch(Exception e)
                        {
                    e.printStackTrace();
                }
                st = null;
            }
            if (conn != null) {
                try {
                    conn.close();
                }
                catch (Exception e) {
                    e.printStackTrace();
                }
                conn = null;
            }
        }
        return 0;
        //表示操作成功
    }
}
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<filter>
<filter-name>ObserveFilter</filter-name>
<filter-class>com.qwserv.itm.pfl.log.svr.ObserveFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>ObserveFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

五.Filter防止用户访问一些未被授权的资源

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package com.drp.util.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;
import javax.servlet.http.HttpSession;
public class AuthFilter implements Filter {
    public void destroy() {
    }
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, 
          FilterChain filterChain) throws IOException, ServletException {
        //1,doFilter方法的第一个参数为ServletRequest对象。此对象给过滤器提供了对进入的信息(包括表单数据、cookie和HTTP请求头)的完全访问。第二个参数为ServletResponse,通常在简单的过滤器中忽略此参数。最后一个参数为FilterChain,此参数用来调用servlet或JSP页。 
        HttpServletRequest request = (HttpServletRequest)servletRequest;
        //;//如果处理HTTP请求,并且需要访问诸如getHeader或getCookies等在ServletRequest中无法得到的方法,就要把此request对象构造成HttpServletRequest 
        HttpServletResponse response = (HttpServletResponse)servletResponse。 
                String currentURL = request.getRequestURI();
        //取得根目录所对应的绝对路径: 
        String targetURL = currentURL.substring(currentURL.indexOf("/", 1), currentURL.length());
        //截取到当前文件名用于比较 
        HttpSession session = request.getSession(false);
        if (!"/login.jsp".equals(targetURL)) {
            //判断当前页是否是重定向以后的登录页面页面,如果是就不做session的判断,防止出现死循环 
            if (session == null || session.getAttribute("user") == null) {
                //*用户登录以后需手动添加session 
                System.out.println("request.getContextPath()=" + request.getContextPath());
                response.sendRedirect(request.getContextPath() + "/login.jsp");
                //如果session为空表示用户没有登录就重定向到login.jsp页面 
                return;
            }
        }
        //加入filter链继续向下执行 
        filterChain.doFilter(request, response);
        //.调用FilterChain对象的doFilter方法。Filter接口的doFilter方法取一个FilterChain对象作为它的一个参数。在调用此对象的doFilter方法时,激活下一个相关的过滤器。如果没有另一个过滤器与servlet或JSP页面关联,则servlet或JSP页面被激活。
    }
    public void init(FilterConfig filterConfig) throws ServletException {
    }
}

html

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<filter>
<filter-name>AuthFilter</filter-name>
<filter-class>com.drp.util.filter.AuthFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>AuthFilter</filter-name>
<url-pattern>*.jsp</url-pattern>//表示对所有jsp文件有效
</filter-mapping>

总结

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原文链接:https://www.cnblogs.com/go4mi/p/5509879.html

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