单一控制器实现员工信息管理

问题

将员工管理的所有操作请求处理合并到一个Servlet中，实现请求的分发。

方案

使用后缀匹配模式，将以do结尾的请求都提交到ActionServlet中，分析do前的操作请求种类，分发到不同的分支执行相应的动作。同时将JDBC以dao和实体的形式来实现，减少分之内的重复代码。

项目结构如下：



步骤

step1: 新建Employee类

新建与t_emp表对应的实体类，属性与表字段一一对应，添加get/set方法及构造函数和toString方法。

[code]package entity;

public class Employee {
    private int id;
    private String name;
    private double salary;
    private int age;

    @Override  //@Override是伪代码,表示重写
    public String toString(){
        return id+" "+name+" "+salary+" "+age;
    }
    public  Employee(){   //无参构造函数
        super();  //调用父类的构造方法
    }
    public  Employee(int id,String name,double salary,int age){//有参构造函数
        super();
        this.id=id;
        this.name=name;
        this.salary=salary;
        this.age=age;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public double getSalary() {
        return salary;
    }
    public void setSalary(double salary) {
        this.salary = salary;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }

}

step2: 新建DBUtil公共类

用于实现数据库的连接和断开的工具类。

[code]package dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
//JDBC管理连接的工具类，可以获取连接和关闭连接
public class DBUtil {
    //获取连接对象
    public static Connection  getConnection() throws Exception{
        Connection conn = null;
        try {
            //1、加载MySQL的JDBC的驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2、取得连接的URL，能访问MySQL数据库的用户名和密码
            String url="jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8";
            String username = "root";
            String password = "123456"; 
            //3、创建与MySQL数据库的连接类的实例
            conn=DriverManager.getConnection(url,username,password);
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }
        return conn;
    }
    //关闭连接对象
    public static void close(Connection conn) throws Exception{
        if(conn!=null){
            try{
                conn.close();
            }catch (SQLException e){
                e.printStackTrace();
                throw e;
            }
        }
    }
}

step 3: 新建EmployeeDAO类

建立针对Employee实体的数据操作类dao。

[code]package dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import javax.swing.text.html.HTMLDocument.HTMLReader.ParagraphAction;

import entity.Employee;

//Employee的数据操作对象，负责Employee的增删改查
public class EmployeeDAO {
    //查询所有员工
    public List<Employee> findAll() throws Exception{
        List<Employee> emps=new ArrayList<Employee>();
        Connection conn=null;
        PreparedStatement stmt=null;
        ResultSet rs=null;
        try {
            conn=DBUtil.getConnection();
            stmt=conn.prepareStatement("select * from t_emp");
            rs=stmt.executeQuery();
            while(rs.next()){
                Employee emp=new Employee(
                    rs.getInt("id"),
                    rs.getString("name"),
                    rs.getDouble("salary"),
                    rs.getInt("age")
                );
                emps.add(emp);
            }
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }finally{
            DBUtil.close(conn);
        }
        return emps;
    }

    //删除员工信息
    public void delete(int id) throws Exception{
        Connection conn=null;
        PreparedStatement stmt=null;
        try {
            conn=DBUtil.getConnection();
            stmt=conn.prepareStatement("delete from t_emp where id=?");
            stmt.setInt(1, id);
            stmt.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }finally{
            DBUtil.close(conn);
        }
    }
    //增加员工信息
    public void save(Employee emp) throws Exception{
        Connection conn=null;
        PreparedStatement stmt=null;
        try {
            conn=DBUtil.getConnection();
            stmt=conn.prepareStatement("insert into t_emp(name,salary,age)" +
                    "values(?,?,?)");
            stmt.setString(1, emp.getName());
            stmt.setDouble(2, emp.getSalary());
            stmt.setInt(3, emp.getAge());
            stmt.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }finally{
            DBUtil.close(conn);
        }
    }

    //根据id 查询员工信息
    public Employee findById(int id) throws Exception{
        Employee emp=null;
        Connection conn=null;
        PreparedStatement stmt=null;
        ResultSet rs=null;
        try {
            conn=DBUtil.getConnection();
            stmt=conn.prepareStatement("select * from t_emp where id=?");
            stmt.setInt(1, id);
            rs=stmt.executeQuery();
            while(rs.next()){
                emp= new Employee(
                        rs.getInt("id"),
                        rs.getString("name"),
                        rs.getDouble("salary"),
                        rs.getInt("age")
                        );
            }
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }
        return emp;
    }
    //修改员工信息
    public void modify(Employee emp) throws Exception{
        Connection conn=null;
        PreparedStatement stmt=null;
        try {
            conn=DBUtil.getConnection();
            stmt=conn.prepareStatement("update t_emp set name=?,salary=?,age=? " +   //age=?后要加空格
                    "where id=?");
            stmt.setString(1, emp.getName());
            stmt.setDouble(2, emp.getSalary());
            System.out.println(emp.getSalary());
            stmt.setInt(3, emp.getAge());
            stmt.setInt(4, emp.getId());
            System.out.println(emp.getId());
            stmt.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
            throw e;
        }finally{
            DBUtil.close(conn);
        }
    }

}

Step 4：新建ActionServlet类

创建用于进行动作分发的ActionServlet类，通过getRequestURI获取请求资源路径，分析do前面的动作种类，执行不同的分支。（Servlet处理部分）

[code]package emp;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import dao.EmployeeDAO;
import entity.Employee;

public class ActionServlet extends HttpServlet{
    @Override
    protected void service(HttpServletRequest request,
            HttpServletResponse response)
            throws ServletException,IOException{
        //保证正确读取Post提交来的中文
        request.setCharacterEncoding("utf-8");
        //保证正确输出中文
        response.setContentType("text/html;charset=utf-8");
        //获取输出流对象，并输出信息
        PrintWriter out=response.getWriter();
        //获取请求资源路径
        String uri=request.getRequestURI();
        //获取请求资源路径中除应用名之外的部分
        String action=uri.substring(uri.lastIndexOf("/")+1,  //获取*.do的*部分内容
                uri.lastIndexOf("."));
        if(action.equals("list")){
            try {
                EmployeeDAO dao=new EmployeeDAO();
                List<Employee> emps = dao.findAll();
                out.println("<table>");
                out.println("<tr><caption>员工信息列表</caption></tr>");  //定义表格标题
                out.println("<tr><td>编号</td><td>姓名</td><td>薪水</td>"+
                               "<td>年龄</td><td>  操作</td></tr>");
                for(Employee emp:emps){
                    out.println("<tr>");
                    out.println("<td>"+emp.getId()+"</td>");
                    out.println("<td>"+emp.getName()+"</td>");
                    out.println("<td>"+emp.getSalary()+"</td>");
                    out.println("<td>"+emp.getAge()+"</td>");
                    out.println("<td><a href='delete.do?id="+emp.getId()+"' "+
                            "onclick=\"return confirm('是否确定删除"+emp.getName()+"');\">删除</a>");
                    out.println("<a href='load.do?id="+emp.getId()+"'>修改</a></td>");
                    out.println("</tr>");
                }
                out.println("</table>");
                out.println("<a href='addEmp.html'>增加新员工</a>");
            } catch (Exception e) {
                e.printStackTrace();
                out.print("系统繁忙");
            }
        }else if(action.equals("add")){
            String name= request.getParameter("name");
            double salary = Double.valueOf(request.getParameter("salary"));
            int age = Integer.valueOf(request.getParameter("age"));
            try {
                Employee emp=new Employee();
                emp.setName(name);
                emp.setSalary(salary);
                emp.setAge(age);
                EmployeeDAO dao=new EmployeeDAO();
                dao.save(emp);
                response.sendRedirect("list.do");
            } catch (Exception e) {
                e.printStackTrace();
                out.print("系统繁忙");
            }
        }else if(action.equals("modify")){
            int id=Integer.valueOf(request.getParameter("id"));
            String name= request.getParameter("name");
            double salary = Double.valueOf(request.getParameter("salary"));
            int age = Integer.valueOf(request.getParameter("age"));
            try {
                Employee emp=new Employee();
                emp.setName(name);
                emp.setSalary(salary);
                emp.setAge(age);
                emp.setId(id);  //保持类的完整性
                EmployeeDAO dao=new EmployeeDAO();
                dao.modify(emp);
                response.sendRedirect("list.do");
            } catch (Exception e) {
                e.printStackTrace();
                out.print("系统繁忙");
            }
        }else if(action.equals("delete")){
                int id=Integer.valueOf(request.getParameter("id"));
            try{
                EmployeeDAO dao=new EmployeeDAO();
                dao.delete(id);
                response.sendRedirect("list.do");
            } catch (Exception e) {
                e.printStackTrace();
                out.print("系统繁忙");
            }
        }else if(action.equals("load")){
            int id=Integer.valueOf(request.getParameter("id"));
            try{
                EmployeeDAO dao=new EmployeeDAO();
                Employee emp = dao.findById(id);
                out.println("<form action='modify.do' method='post'>");//输出表单
                out.println("编号："+ id + "<br>");
                out.println("<input type='hidden' name='id' value='"+emp.getId()+"'/><br>");
                out.println("姓名：<input name='name' value='"+emp.getName()+"'/><br>");
                out.println("薪水：<input name='salary' value='"+emp.getSalary()+"'/><br>");
                out.println("年龄：<input name='age' value='"+emp.getAge()+"'/><br>");
                out.println("<input type='submit' value='修改'/>");
                out.println("</form>");
                out.println("</body></html>");
                //response.sendRedirect("list.do");
            } catch (Exception e) {
                e.printStackTrace();
                out.print("系统繁忙");
            }
        }
    }
}

Step 5: 新建addEmp.html

新建用于完成增加员工的表单页面。

[code]<body style="font-size:24px">
    <form action="add.do" method="post"> 
        <fieldset>
            <legend>添加员工</legend>
            姓名：<input name="name"/><br>
            薪水：<input name="salary"/><br> 
            年龄：<input name="age"/><br>
            <input type="submit" value="添加">
        </fieldset>
    </form>
  </body>

Step 6: 修改web.xml

使用后缀匹配模式配置ActionServlet的映射原则。

[code]<!-- 合并员工管理多请求 -->
  <servlet>
    <servlet-name>actionServlet</servlet-name>
    <servlet-class>emp.ActionServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>actionServlet</servlet-name>
    <url-pattern>*.do</url-pattern>  
 </servlet-mapping>

Step7：部署应用，访问

页面如下：



===================

到此，项目就搭建成功了。实现的也是增删改查功能，与之前不同的是，这里采用后缀匹配模式，即*.do,实现了单一控制器（Servlet）管理员工信息。表面来看是在web.xml配置中少写了很多、，实际上也精简了很多代码，有分层管理代码的思路，看起来更清晰。