-------------------siwuxie095
使用过滤器进行权限校验
一个简单的权限校验过滤器实例：
登录状态校验：如果没有成功登录就没有权限访问特定页面
当访问首页要进入 hello.jsp 页面时，首先判断是否处于登录状态：
（1）如果是，直接点击进入 hello.jsp
（2）如果否，则点击 hello.jsp 时进入 login.jsp，登录成功后自动跳转回 hello.jsp
工程结构目录如下：
后端代码：
LoginServlet.java：
package com.siwuxie095.servlet;
import java.io.IOException;
import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;
// LoginServlet 继承自 HttpServlet public class LoginServlet extends HttpServlet { /** * 用于序列化和反序列化的 ID */ private static final long serialVersionUID = -7740192486028671728L;
//覆盖父类 HttpServlet 的 doGet() 方法 @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println("===== doGet ====="); //在 doGet() 方法里调用 doPost() 方法 //这样，GET请求和POST请求可以共用一套处理逻辑 doPost(req, resp); }
//覆盖父类 HttpServlet 的 doPost() 方法 @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { System.out.println("===== doPost ====="); String userName=req.getParameter("uname"); String password=req.getParameter("upwd"); /** * returnUri是用户访问登录页面之前所访问的页面 * 通过这个值，登录成功后，可以跳转回登录前的页面 */ String returnUri=req.getParameter("return_uri"); System.out.println("用户名："+userName); System.out.println("密码："+password); System.out.println("return uri："+returnUri);
String forward=null;
if (userName.equals("李白")&&password.equals("8888")) { //如果用户登录成功，就在当前用户的session对象中 //保存key为flag，value为login_success的字符串 //表明当前用户处于登录状态 req.getSession().setAttribute("flag", "login_success");
//如果returnUri不为空，就进入用户访问登录页面之前所访问的页面 if (returnUri!=null) { forward=returnUri; }else{ forward="/index.jsp"; }
}else { req.getSession().setAttribute("flag", "login_error"); req.setAttribute("msg", "用户名或密码错误！！！"); forward="/login.jsp"; }
RequestDispatcher rd=req.getRequestDispatcher(forward); rd.forward(req, resp); }
} |
LogoutServlet.java：
package com.siwuxie095.servlet;
import java.io.IOException;
import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;
public class LogoutServlet extends HttpServlet { private static final long serialVersionUID = 1L;
public LogoutServlet() { super(); }
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doPost(req, resp); }
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //退出逻辑，直接删除session对象 req.getSession().invalidate(); //跳转回首页 resp.sendRedirect(req.getContextPath()+"/index.jsp"); }
} |
EncodingFilter.java：
package com.siwuxie095.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;
public class EncodingFilter implements Filter {
//声明一个成员变量 用来保存当前应用的字符集名称 private String charEncoding=null;
public EncodingFilter() {
}
public void init(FilterConfig fConfig) throws ServletException { //在部署描述符中设置该应用的默认字符编码集 在init方法中获取到该设置 charEncoding=fConfig.getInitParameter("encoding"); //如果字符编码的名称没有设置 就抛出一个异常 if (charEncoding==null) { throw new ServletException("EncodingFilter中的编码设置为空！！！"); } }
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { //如果当前应用的默认编码，与请求中的编码值不一致 if (!charEncoding.equals(request.getCharacterEncoding())) { //那么就将请求中的编码设置成当前默认的编码设置 request.setCharacterEncoding(charEncoding); }
//将响应的编码设置也改成当前默认的编码设置 response.setCharacterEncoding(charEncoding); chain.doFilter(request, response); }
public void destroy() {
}
} |
PermissionFilter.java：
package com.siwuxie095.filter;
import java.io.IOException; import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.RequestDispatcher; 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 PermissionFilter implements Filter {
public PermissionFilter() {
}
public void init(FilterConfig fConfig) throws ServletException {
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { /** * 首先将参数中的ServletRequest和ServletResponse强制转换为 * HttpServletRequest和HttpServletResponse */ HttpServletRequest req = (HttpServletRequest) request; HttpServletResponse resp = (HttpServletResponse) response;
// 获取请求中的ServletPath，即servlet的路径 String servletPath = req.getServletPath();
// 获取session对象 HttpSession session = req.getSession();
// 获取session对象中的flag值，需强转 String flag = (String) session.getAttribute("flag");
// 如果用户访问的是首页index.jsp 或者是login.jsp //或者执行登录操作 那么就将请求转发给下一个组件进行处理 if (servletPath != null && (servletPath.equals("/login.jsp") || (servletPath.equals("/index.jsp")) || (servletPath.equals("/loginServlet")))) {
chain.doFilter(request, response);
} else {
/** * 业务逻辑： 对于请求的其他url都会进行权限校验 * * 如果用户处于登录状态 可以直接进行访问 */ if (flag != null && flag.equals("login_success")) {
chain.doFilter(request, response);
} else if (flag != null && flag.equals("login_error")) { /** * 如果用户登录失败 返回login.jsp * 同时提示用户，登录失败 */ req.setAttribute("msg", "登录失败，请重新登录！！！<br/>");
// 把用户所访问的url保存到request对象中 req.setAttribute("return_uri", servletPath); RequestDispatcher rd = req.getRequestDispatcher("/login.jsp"); rd.forward(req, resp);
} else {
// 如果用户没有登录 同样也返回login.jsp 提示尚未登录 req.setAttribute("msg", "您尚为登录！！！");
// 同样将用户访问的url保存到request对象中 req.setAttribute("return_uri", servletPath); RequestDispatcher rd = req.getRequestDispatcher("/login.jsp"); rd.forward(req, resp);
} }
}
public void destroy() {
}
} |
前端代码：
login.jsp：
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>登录页面</title>
<script type="text/javascript"> function check(form){ if(document.forms.loginForm.uname.value==""){ alert("请输入用户名！"); document.forms.loginForm.uname.focus(); return false; } if(document.forms.loginForm.upwd.value==""){ alert("请输入密码！"); document.forms.loginForm.upwd.focus(); return false; } } </script>
<style type="text/css"> body { color: #000; font-size =14px; margin: 20px, auto; } </style>
</head> <body>
<!-- 添加表单，url在部署描述符中进行配置，使用post方式来提交 --> <form action="<%= request.getContextPath() %>/loginServlet" method="post" name="loginForm">
<!-- 添加一个隐藏域，用于保存returnUri --> <% if(request.getAttribute("return_uri")!=null){ %>
<input type="hidden" name="return_uri" value="<%= request.getAttribute("return_uri") %>" />
<% } %>
<table border="1" cellspacing="0" cellpadding="5" bordercolor="silver" align="center"> <tr> <td colspan="2" align="center" bgcolor="#E8E8E8">用户登录</td> </tr> <tr> <td>用户名：</td> <td><input type="text" name="uname" /></td> </tr> <tr> <td>密码：</td> <td><input type="password" name="upwd" /></td> </tr> <tr> <td colspan="2" align="center"> <input type="submit" name="submit" onclick="return check(this);" /> <input type="reset" name="reset" /> </td> </tr> </table> </form>
</body> </html> |
index.jsp：
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>首页</title> </head> <body>
首页<br/><br/>
<a href="<%=request.getContextPath() %>/hello.jsp">hello.jsp</a><br/>
<%-- 从 session 中获取用户的登录状态 --%> <% String flag = ""; Object obj=session.getAttribute("flag");
if(obj!=null){ flag=obj.toString(); }
if(flag.equals("login_success")){ %> <a href="<%= request.getContextPath() %>/logoutServlet">退出</a> <% }else{ %> <a href="<%= request.getContextPath() %>/login.jsp">登录</a> <% } %>
</body> </html> |
hello.jsp：
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Hello World</title> </head> <body> <% out.print("Hello World<br/>"); %> <a href="<%= request.getContextPath() %>/index.jsp">首页</a> </body> </html> |
在部署描述符 web.xml 中注册 servlet 和 filter：
<?xml version="1.0" encoding="UTF-8"?> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1"> <display-name>MyFilter</display-name> <welcome-file-list> <welcome-file>index.html</welcome-file> <welcome-file>index.htm</welcome-file> <welcome-file>index.jsp</welcome-file> <welcome-file>default.html</welcome-file> <welcome-file>default.htm</welcome-file> <welcome-file>default.jsp</welcome-file> </welcome-file-list>
<servlet> <servlet-name>LoginServlet</servlet-name> <servlet-class>com.siwuxie095.servlet.LoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginServlet</servlet-name> <url-pattern>/loginServlet</url-pattern> </servlet-mapping>
<servlet> <servlet-name>LogoutServlet</servlet-name> <servlet-class>com.siwuxie095.servlet.LogoutServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LogoutServlet</servlet-name> <url-pattern>/logoutServlet</url-pattern> </servlet-mapping>
<filter> <filter-name>EncodingFilter</filter-name> <filter-class>com.siwuxie095.filter.EncodingFilter</filter-class> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> </filter> <filter-mapping> <filter-name>EncodingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>
<filter> <filter-name>PermissionFilter</filter-name> <filter-class>com.siwuxie095.filter.PermissionFilter</filter-class> </filter> <filter-mapping> <filter-name>PermissionFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>
</web-app> |
部署描述符 web.xml 在 WEB-INF 目录下，如果没有，手动创建即可
选择工程 MyFilter，右键->Java EE Tools->Generate Deployment Descriptor Stub
访问：localhost:8080/MyFilter/index.jsp
点击 hello.jsp，跳转到：localhost:8080/MyFilter/hello.jsp，
分别输入 李白 和 8888
登录成功，跳转回 hello.jsp 页面的内容
点击 首页，此时 index.jsp 页面的内容
【made by siwuxie095】