JAVA-EE使用Filter改造OA项目登录------计算机网络经典

野性酷女 2024-02-21 11:41 32阅读 0赞

>     Filter过滤器
>     每一个Servlet都需要解决自己业务的问题,但是它们都需要判断用户是否已经登陆,
>     如果登陆了,才可以执行后续操作,如果没有则需要登录
>     这部分我们可以使用Filter过滤器来将这部分从Servlet中抽离,达到复用效果
>     我们可以把Servlet程序看作是需要执行的目标,我们可以使用过滤器Filter来添加过滤代码
>     Filter可以添加到Servlet执行之前也可以是执行之后
>     过滤器也是根据请求路径来执行的
>     Servlet对象默认情况下,服务器启动,不会创建对象
>     Filter对象默认在服务器启动创建对象
>     chain.doFilter()
>     这行代码用来放行,执行下一个过滤器,如果没有过滤器,执行最终的servlet
>     注意Filter的优先级比Servlet高
>     XML配置和注解配置都会让tomcat服务器创建对象,因为这个是伪单例模式
>     会有两个同名的对象存在,一起执行方法
>     在web.xml配置时,filter-mapping配置越靠上,优先级越高
>     过滤器优先顺序遵循的栈数据结构
>     Filter的执行顺序根据filter类名的先后优先级顺序,比较的是整个类的类名
>     在字典中的排序
> 
>     Filter过滤器
>     每一个Servlet都需要解决自己业务的问题,但是它们都需要判断用户是否已经登陆,
>     如果登陆了,才可以执行后续操作,如果没有则需要登录
>     这部分我们可以使用Filter过滤器来将这部分从Servlet中抽离,达到复用效果
>     我们可以把Servlet程序看作是需要执行的目标,我们可以使用过滤器Filter来添加过滤代码
>     Filter可以添加到Servlet执行之前也可以是执行之后
>     过滤器也是根据请求路径来执行的
>     Servlet对象默认情况下,服务器启动,不会创建对象
>     Filter对象默认在服务器启动创建对象
>     chain.doFilter()
>     这行代码用来放行,执行下一个过滤器,如果没有过滤器,执行最终的servlet
>     注意Filter的优先级比Servlet高
>     XML配置和注解配置都会让tomcat服务器创建对象,因为这个是伪单例模式
>     会有两个同名的对象存在,一起执行方法
>     在web.xml配置时,filter-mapping配置越靠上,优先级越高
>     过滤器优先顺序遵循的栈数据结构
>     Filter的执行顺序根据filter类名的先后优先级顺序,比较的是整个类的类名
>     在字典中的排序

>     package com.bjpowernode.oa.filter;
>     
>     import jakarta.servlet.*;
>     import jakarta.servlet.http.HttpServletRequest;
>     import jakarta.servlet.http.HttpServletResponse;
>     import jakarta.servlet.http.HttpSession;
>     
>     import java.io.IOException;
>     
>     public class LoginFilter implements Filter {
>         @Override
>         public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException
>         {
>             HttpServletRequest request = (HttpServletRequest)req;
>             HttpServletResponse response = (HttpServletResponse)res;
>             request.setCharacterEncoding("UTF-8");
>             response.setContentType("text/html;charset=UTF-8");
>             HttpSession session = request.getSession(false);
>             if(session != null && session.getAttribute("username") != null)
>             {
>                 chain.doFilter(request,response);
>             }
>             else
>             {
>                 response.sendRedirect(request.getContextPath() + "/index.jsp");
>             }
>         }
>     }
> 
>     package com.bjpowernode.oa.filter;
>     
>     import jakarta.servlet.*;
>     import jakarta.servlet.http.HttpServletRequest;
>     import jakarta.servlet.http.HttpServletResponse;
>     import jakarta.servlet.http.HttpSession;
>     
>     import java.io.IOException;
>     
>     public class LoginFilter implements Filter {
>         @Override
>         public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException
>         {
>             HttpServletRequest request = (HttpServletRequest)req;
>             HttpServletResponse response = (HttpServletResponse)res;
>             request.setCharacterEncoding("UTF-8");
>             response.setContentType("text/html;charset=UTF-8");
>             HttpSession session = request.getSession(false);
>             if(session != null && session.getAttribute("username") != null)
>             {
>                 chain.doFilter(request,response);
>             }
>             else
>             {
>                 response.sendRedirect(request.getContextPath() + "/index.jsp");
>             }
>         }
>     }

>     <?xml version="1.0" encoding="UTF-8"?>
>     <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
>              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>              xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
>              version="4.0">
>         <session-config>
>     
>             <session-timeout>30</session-timeout>
>         </session-config>
>     
>         <welcome-file-list>
>             <welcome-file>Welcome</welcome-file>
>         </welcome-file-list>
>     
>         <filter>
>             <filter-name>loginFilter</filter-name>
>             <filter-class>com.bjpowernode.oa.filter.LoginFilter</filter-class>
>         </filter>
>         <filter-mapping>
>             <filter-name>loginFilter</filter-name>
>     
>     
>             <url-pattern>/dept/*</url-pattern>
>         </filter-mapping>
>     </web-app>
> 
>     <?xml version="1.0" encoding="UTF-8"?>
>     <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
>              xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>              xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
>              version="4.0">
>         <session-config>
>     
>             <session-timeout>30</session-timeout>
>         </session-config>
>     
>         <welcome-file-list>
>             <welcome-file>Welcome</welcome-file>
>         </welcome-file-list>
>     
>         <filter>
>             <filter-name>loginFilter</filter-name>
>             <filter-class>com.bjpowernode.oa.filter.LoginFilter</filter-class>
>         </filter>
>         <filter-mapping>
>             <filter-name>loginFilter</filter-name>
>     
>     
>             <url-pattern>/dept/*</url-pattern>
>         </filter-mapping>
>     </web-app>

>     package com.bjpowernode.oa.web.action;
>     
>     import com.bjpowernode.oa.utils.DBUtil;
>     import com.bjpowernode.oa.web.Pojo.Dept;
>     import jakarta.servlet.ServletException;
>     import jakarta.servlet.annotation.WebServlet;
>     import jakarta.servlet.http.HttpServlet;
>     import jakarta.servlet.http.HttpServletRequest;
>     import jakarta.servlet.http.HttpServletResponse;
>     
>     import java.io.IOException;
>     import java.sql.Connection;
>     import java.sql.PreparedStatement;
>     import java.sql.ResultSet;
>     import java.sql.SQLException;
>     import java.util.ArrayList;
>     import java.util.List;
>     
>     @WebServlet(urlPatterns = {"/dept/list","/dept/detail","/dept/delete","/dept/save","/dept/edit"})
>     public class DeptServlet extends HttpServlet
>     {
>         @Override
>         protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             String servletPath = request.getServletPath();
>             if("/dept/list".equals(servletPath))
>             {
>                 doList(request,response);
>             }
>             else if("/dept/detail".equals(servletPath))
>             {
>                 doDetail(request,response);
>             }
>             else if("/dept/delete".equals(servletPath))
>             {
>                 doDel(request,response);
>             }
>             else if("/dept/save".equals(servletPath))
>             {
>                 doSave(request,response);
>             }
>             else if("/dept/edit".equals(servletPath))
>             {
>                 doModify(request,response);
>             }
>         }
>     
>         private void doModify(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             Integer deptno = Integer.parseInt(request.getParameter("deptno"));
>             String dname = request.getParameter("dname");
>             String loc = request.getParameter("loc");
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             int count = 0;
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 connection.setAutoCommit(false);
>                 String sql = "update dept set dname = ?,loc = ? where deptno = ?";
>                 statement = connection.prepareStatement(sql);
>                 statement.setString(1,dname);
>                 statement.setString(2,loc);
>                 statement.setInt(3,deptno);
>                 count = statement.executeUpdate();
>                 connection.commit();
>             }
>             catch (SQLException e)
>             {
>                 if (connection != null)
>                 {
>                     try
>                     {
>                         connection.rollback();
>                     }
>                     catch (SQLException ex)
>                     {
>                         throw new RuntimeException(ex);
>                     }
>                 }
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>             if(count == 1)
>             {
>                 response.sendRedirect(request.getContextPath() +  "/dept/list");
>             }
>             else
>             {
>                 response.sendRedirect(request.getContextPath() + "/Error.jsp");
>             }
>         }
>     
>         private void doSave(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             Integer deptno = Integer.parseInt(request.getParameter("deptno"));
>             String dname = request.getParameter("dname");
>             String loc = request.getParameter("loc");
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             int count = 0;
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 connection.setAutoCommit(false);
>                 String sql = "insert into dept(deptno,dname,loc) values(?,?,?)";
>                 statement = connection.prepareStatement(sql);
>                 statement.setInt(1,deptno);
>                 statement.setString(2,dname);
>                 statement.setString(3,loc);
>                 count = statement.executeUpdate();
>                 connection.commit();
>     
>             }
>             catch (SQLException e)
>             {
>                 if (connection != null)
>                 {
>                     try
>                     {
>                         connection.rollback();
>                     }
>                     catch (SQLException ex)
>                     {
>                         throw new RuntimeException(ex);
>                     }
>                 }
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>             if(count == 1)
>             {
>                 response.sendRedirect(request.getContextPath() +  "/dept/list");
>             }
>             else
>             {
>                 response.sendRedirect(request.getContextPath() + "/Error.jsp");
>             }
>         }
>     
>         private void doDel(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             String deptno = request.getParameter("deptno");
>             int count = 0;
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 connection.setAutoCommit(false);
>                 String sql = "delete from dept where deptno = ?";
>                 statement = connection.prepareStatement(sql);
>                 statement.setString(1,deptno);
>                 count = statement.executeUpdate();
>                 connection.commit();
>             }
>             catch (SQLException e)
>             {
>                 if (connection != null)
>                 {
>                     try
>                     {
>                         connection.rollback();
>                     }
>                     catch (SQLException ex)
>                     {
>                         throw new RuntimeException(ex);
>                     }
>                 }
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>             if(count == 1)
>             {
>                 response.sendRedirect(request.getContextPath() + "/dept/list");
>             }
>             else
>             {
>                 response.sendRedirect(request.getContextPath() + "/Error.jsp");
>             }
>         }
>     
>         private void doDetail(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             String deptno = request.getParameter("deptno");
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 String sql = "select * from dept where deptno = ?";
>                 statement = connection.prepareStatement(sql);
>                 statement.setString(1,deptno);
>                 resultSet = statement.executeQuery();
>                 if(resultSet.next())
>                 {
>                     String dname = resultSet.getString("dname");
>                     String loc = resultSet.getString("loc");
>                     Dept dept = new Dept(deptno,dname,loc);
>                     request.setAttribute("dept",dept);
>                 }
>             }
>             catch (SQLException e)
>             {
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>             String flag = request.getParameter("f");
>             if("d".equals(flag))
>             {
>                 request.getRequestDispatcher("/detail.jsp").forward(request,response);
>             }
>             if("m".equals(flag))
>             {
>                 request.getRequestDispatcher("/edit.jsp").forward(request,response);
>             }
>         }
>     
>         private void doList(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             //连接数据库,查询所有部门信息
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             List<Dept> list = new ArrayList<Dept>();
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 String sql = "select * from dept";
>                 statement = connection.prepareStatement(sql);
>                 resultSet = statement.executeQuery();
>                 while(resultSet.next())
>                 {
>                     String deptno = resultSet.getString("deptno");
>                     String dname = resultSet.getString("dname");
>                     String loc = resultSet.getString("loc");
>                     Dept dept = new Dept(deptno,dname,loc);
>                     list.add(dept);
>                 }
>                 request.setAttribute("depts",list);
>                 request.getRequestDispatcher("/list.jsp").forward(request,response);
>             }
>             catch (SQLException e)
>             {
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>         }
>     }
> 
>     package com.bjpowernode.oa.web.action;
>     
>     import com.bjpowernode.oa.utils.DBUtil;
>     import com.bjpowernode.oa.web.Pojo.Dept;
>     import jakarta.servlet.ServletException;
>     import jakarta.servlet.annotation.WebServlet;
>     import jakarta.servlet.http.HttpServlet;
>     import jakarta.servlet.http.HttpServletRequest;
>     import jakarta.servlet.http.HttpServletResponse;
>     
>     import java.io.IOException;
>     import java.sql.Connection;
>     import java.sql.PreparedStatement;
>     import java.sql.ResultSet;
>     import java.sql.SQLException;
>     import java.util.ArrayList;
>     import java.util.List;
>     
>     @WebServlet(urlPatterns = {"/dept/list","/dept/detail","/dept/delete","/dept/save","/dept/edit"})
>     public class DeptServlet extends HttpServlet
>     {
>         @Override
>         protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             String servletPath = request.getServletPath();
>             if("/dept/list".equals(servletPath))
>             {
>                 doList(request,response);
>             }
>             else if("/dept/detail".equals(servletPath))
>             {
>                 doDetail(request,response);
>             }
>             else if("/dept/delete".equals(servletPath))
>             {
>                 doDel(request,response);
>             }
>             else if("/dept/save".equals(servletPath))
>             {
>                 doSave(request,response);
>             }
>             else if("/dept/edit".equals(servletPath))
>             {
>                 doModify(request,response);
>             }
>         }
>     
>         private void doModify(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             Integer deptno = Integer.parseInt(request.getParameter("deptno"));
>             String dname = request.getParameter("dname");
>             String loc = request.getParameter("loc");
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             int count = 0;
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 connection.setAutoCommit(false);
>                 String sql = "update dept set dname = ?,loc = ? where deptno = ?";
>                 statement = connection.prepareStatement(sql);
>                 statement.setString(1,dname);
>                 statement.setString(2,loc);
>                 statement.setInt(3,deptno);
>                 count = statement.executeUpdate();
>                 connection.commit();
>             }
>             catch (SQLException e)
>             {
>                 if (connection != null)
>                 {
>                     try
>                     {
>                         connection.rollback();
>                     }
>                     catch (SQLException ex)
>                     {
>                         throw new RuntimeException(ex);
>                     }
>                 }
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>             if(count == 1)
>             {
>                 response.sendRedirect(request.getContextPath() +  "/dept/list");
>             }
>             else
>             {
>                 response.sendRedirect(request.getContextPath() + "/Error.jsp");
>             }
>         }
>     
>         private void doSave(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             Integer deptno = Integer.parseInt(request.getParameter("deptno"));
>             String dname = request.getParameter("dname");
>             String loc = request.getParameter("loc");
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             int count = 0;
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 connection.setAutoCommit(false);
>                 String sql = "insert into dept(deptno,dname,loc) values(?,?,?)";
>                 statement = connection.prepareStatement(sql);
>                 statement.setInt(1,deptno);
>                 statement.setString(2,dname);
>                 statement.setString(3,loc);
>                 count = statement.executeUpdate();
>                 connection.commit();
>     
>             }
>             catch (SQLException e)
>             {
>                 if (connection != null)
>                 {
>                     try
>                     {
>                         connection.rollback();
>                     }
>                     catch (SQLException ex)
>                     {
>                         throw new RuntimeException(ex);
>                     }
>                 }
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>             if(count == 1)
>             {
>                 response.sendRedirect(request.getContextPath() +  "/dept/list");
>             }
>             else
>             {
>                 response.sendRedirect(request.getContextPath() + "/Error.jsp");
>             }
>         }
>     
>         private void doDel(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             String deptno = request.getParameter("deptno");
>             int count = 0;
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 connection.setAutoCommit(false);
>                 String sql = "delete from dept where deptno = ?";
>                 statement = connection.prepareStatement(sql);
>                 statement.setString(1,deptno);
>                 count = statement.executeUpdate();
>                 connection.commit();
>             }
>             catch (SQLException e)
>             {
>                 if (connection != null)
>                 {
>                     try
>                     {
>                         connection.rollback();
>                     }
>                     catch (SQLException ex)
>                     {
>                         throw new RuntimeException(ex);
>                     }
>                 }
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>             if(count == 1)
>             {
>                 response.sendRedirect(request.getContextPath() + "/dept/list");
>             }
>             else
>             {
>                 response.sendRedirect(request.getContextPath() + "/Error.jsp");
>             }
>         }
>     
>         private void doDetail(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             String deptno = request.getParameter("deptno");
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 String sql = "select * from dept where deptno = ?";
>                 statement = connection.prepareStatement(sql);
>                 statement.setString(1,deptno);
>                 resultSet = statement.executeQuery();
>                 if(resultSet.next())
>                 {
>                     String dname = resultSet.getString("dname");
>                     String loc = resultSet.getString("loc");
>                     Dept dept = new Dept(deptno,dname,loc);
>                     request.setAttribute("dept",dept);
>                 }
>             }
>             catch (SQLException e)
>             {
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>             String flag = request.getParameter("f");
>             if("d".equals(flag))
>             {
>                 request.getRequestDispatcher("/detail.jsp").forward(request,response);
>             }
>             if("m".equals(flag))
>             {
>                 request.getRequestDispatcher("/edit.jsp").forward(request,response);
>             }
>         }
>     
>         private void doList(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
>         {
>             //连接数据库,查询所有部门信息
>             Connection connection = null;
>             PreparedStatement statement = null;
>             ResultSet resultSet = null;
>             List<Dept> list = new ArrayList<Dept>();
>             try
>             {
>                 connection = DBUtil.getConnection();
>                 String sql = "select * from dept";
>                 statement = connection.prepareStatement(sql);
>                 resultSet = statement.executeQuery();
>                 while(resultSet.next())
>                 {
>                     String deptno = resultSet.getString("deptno");
>                     String dname = resultSet.getString("dname");
>                     String loc = resultSet.getString("loc");
>                     Dept dept = new Dept(deptno,dname,loc);
>                     list.add(dept);
>                 }
>                 request.setAttribute("depts",list);
>                 request.getRequestDispatcher("/list.jsp").forward(request,response);
>             }
>             catch (SQLException e)
>             {
>                 throw new RuntimeException(e);
>             }
>             finally
>             {
>                 DBUtil.close(connection,statement,resultSet);
>             }
>         }
>     }