重温 Servlet

蔚落 2022-06-10 04:20 165阅读 0赞

### 前言 ###

**已经有几百年没碰servlet了，前天觉得公司查看打卡记录很不方便，于是有了一个想法，做一个给同事们查看打卡记录的app，领导觉得很好，便下午开工了，这是个小应用，服务端当然不会用ssm了，用jdbc即可，再想想用回servlet好了，毕竟当年也是servlet入门的，对韩顺平老师的超强sqlHelper至今记忆犹新。**

#### **Servlet3.1**　新特性： ####

*  在Servlet 3.0中,一些新的注释javax.servlet.annotation介绍了包。我们在web上使用的配置。xml现在可以通过使用注释来实现。
 *  现在，我们可以没有web . xml的Servlet、过滤器ServletContextListener。
 *  它们只打算提供元数据，我们仍然需要扩展相应的类或实现相应的接口。
 *  在web inf / classes目录或在web inf / lib中的jar中扫描注释。
 *  扫描在部署时完成。
 *  如果在web - inf / lib中有很多JAR文件，那么servlet容器的启动可能会非常慢，因为每一个JAR文件中的每一个类文件都必须被扫描。我们可以通过在web . xml中使用metadata - complete =“true”来关闭jar扫描。
 *  网络。xml仍然可以被选择性地覆盖注释配置。
 *  使用注释，我们没有办法配置类似的东西:提供一个欢迎页面列表、定义错误页面和提供筛选器顺序。我们必须使用web . xml。这些注释是为了提高开发人员的生产力而引入的。它们有更好的默认值，并基于约定优于配置范型。

![这里写图片描述][SouthEast]

![这里写图片描述][SouthEast 1]

### 项目结构 ###

**韩顺平经典的结构，controller -> service -> sqlHelper , 很简单的应用，没用接口编程，直接用类传递。**

![这里写图片描述][SouthEast 2]

#### **这里给出后端代码** ####

*  User.java

package com.xfoce.domain;
    
    import java.util.Date;
    
    public class User { 
    
        private Integer id;
    
        private String username;
    
        private String password;
    
        private String email;
    
        private Integer status;
    
        private Date regTime;
    
        public Integer getId() {
            return id;
        }
    
        public void setId(Integer id) {
            this.id = id;
        }
    
        public String getUsername() {
            return username;
        }
    
        public void setUsername(String username) {
            this.username = username;
        }
    
        public String getPassword() {
            return password;
        }
    
        public void setPassword(String password) {
            this.password = password;
        }
    
        public String getEmail() {
            return email;
        }
    
        public void setEmail(String email) {
            this.email = email;
        }
    
        public Integer getStatus() {
            return status;
        }
    
        public void setStatus(Integer status) {
            this.status = status;
        }
    
        public Date getRegTime() {
            return regTime;
        }
    
        public void setRegTime(Date regTime) {
            this.regTime = regTime;
        }
    
        @Override
        public String toString() {
            return "User [id=" + id + ", username=" + username + ", password="
                    + password + ", email=" + email + ", status=" + status
                    + ", regTime=" + regTime + "]";
        }
    
    }

*  UserService.java

package com.xforce.service;
    
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    import java.util.Set;
    
    import com.xfoce.domain.User;
    import com.xforce.utils.DateUtil;
    import com.xforce.utils.SqlHelper;
    
    public class UserService {
    
        //添加user
        public void addUser(User user) {
            String sql = "insert into a_user(username, password, email, status) values(?,?,?,?)";
            String[] parameters = {user.getUsername(),user.getPassword(),user.getEmail(),user.getStatus()+"", DateUtil.StringToDate(new Date())};
            SqlHelper.executeUpdate(sql, parameters);
        }
    
        //验证user
        public User checkUser(User user) {
            String sql = "select * from a_user where username = ? and password = ?";
            String[] parameters = {user.getUsername(),user.getPassword()};
            ResultSet result = SqlHelper.executeQuery(sql, parameters);
            User s_user = new User();
            List<User> users = new ArrayList<User>();
            try {
                while(result.next()) {
                    s_user.setId(result.getInt("id"));
                    s_user.setEmail(result.getString("email"));
                    s_user.setStatus(result.getInt("status"));
                    s_user.setRegTime(result.getDate("reg_time"));
                    s_user.setUsername(result.getString("username"));
                    s_user.setPassword(result.getString("password"));
                    users.add(s_user);
                }
    
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            if(users.size() == 0 || users == null) {
                return null;
            }
            else{
                return users.get(0);
            }
    
        }
    
    }

*  SqlHelper.java

package com.xforce.utils;
    import java.io.IOException;
    import java.io.InputStream;
    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    import java.util.Properties;
    import java.sql.*;
    public class SqlHelper { 
        //定义变量
        private static Connection ct = null;
        //大多数情况下用preparedstatement替代statement
        private static PreparedStatement ps = null;
        private static ResultSet rs = null;
    
        //连接数据库的参数
        private static String url = "";
        private static String username = "";
        private static String driver = "";
        private static String passwd = "";
    
        private static CallableStatement cs = null;
        public static CallableStatement getCs()
        {
            return cs;
        }
        private static Properties  pp = null;
        private static InputStream fis = null;
        //加载驱动，只需要一次，用静态代码块
        static
        {
            try
            {
                //从dbinfo.properties
                pp = new Properties();
                fis=SqlHelper.class.getClassLoader().getResourceAsStream("jdbc.properties");
                //fis = new FileInputStream();
                pp.load(fis);
                url = pp.getProperty("jdbcUrl");
                username = pp.getProperty("username");
                driver = pp.getProperty("driverClasss");
                passwd = pp.getProperty("password");
    
                Class.forName(driver);
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }
            finally
            {
                try
                { fis.close();}
                catch(IOException e) {e.printStackTrace();}
                fis = null;//垃圾回收站上收拾
            }
    
        }
        //得到连接
        public static Connection getConnection()
            {
                try
                {ct = DriverManager.getConnection(url,username,passwd);}
                catch(Exception e) {e.printStackTrace();}
                return ct;
            }
    
    
    //*************callPro1存储过程函数1************* 
        public static CallableStatement callPro1(String sql,String[] parameters)
        {
            try{
                ct = getConnection();
                cs = ct.prepareCall(sql);
                if(parameters!=null){
                    for(int i=0;i<parameters.length;i++){
                     cs.setObject(i+1,parameters[i]);
                    }
                }   
                cs.execute();
            }
            catch(Exception e) { e.printStackTrace(); throw new RuntimeException(e.getMessage());}
            finally
            { close(rs,cs,ct);}
            return cs;
        }
    
    //*******************callpro2存储过程2************************
    public static CallableStatement callPro2(String sql,String[] inparameters,
    Integer[] outparameters)
    {
        try
        {
            ct = getConnection();
            cs = ct.prepareCall(sql);
            if(inparameters!=null)
            {
                for(int i=0;i<inparameters.length;i++)
                {
                    cs.setObject(i+1,inparameters[i]);
                }
            }
        //cs.registerOutparameter(2,oracle.jdbc.OracleTypes.CURSOR);
            if(outparameters!=null)
            {
                for(int i=0;i<outparameters.length;i++)
                {
                    cs.registerOutParameter(inparameters.length+1+i,outparameters[i]);
                }
            }
            cs.execute();
        }
        catch(Exception e) {
            e.printStackTrace(); throw new RuntimeException(e.getMessage());
        }
        finally
        {
    
        }
        return cs;
    }
        public static ResultSet executeQuery(String sql,String[] parameters)
        {
            try
            {
                ct=getConnection();
                ps=ct.prepareStatement(sql);
                if(parameters!=null)
                {
                    for(int i=0;i<parameters.length;i++)
                    {
                        ps.setString(i+1,parameters[i]);
                    }
                }
                rs = ps.executeQuery();
            }
            catch(Exception e)
            {
                e.printStackTrace();
                throw new RuntimeException(e.getMessage());
            }
            finally
            {
    
            }
            return rs;
        }
    
    
        public static Connection getCt()
        {
            return ct;
        }
        public static PreparedStatement getPs()
        {
            return ps;
        }
        public static ResultSet getRs()
        {
            return rs;
        }
    
    
        public static void executeUpdate2(String[] sql,String[][] parameters)
        {
            try
            {
                ct = getConnection();
                ct.setAutoCommit(false);
    
                for(int i=0;i<sql.length;i++)
                {
    
                    if(null!=parameters[i])
                    {
                        ps = ct.prepareStatement(sql[i]);
                        for(int j=0;j<parameters[i].length;j++)
                        {
                            ps.setString(j+1,parameters[i][j]);
                        }
                        ps.executeUpdate();
                    }
    
                }
    
    
                ct.commit();
    
    
            }catch (Exception e)
            {
                e.printStackTrace();
                try
                {
                    ct.rollback();
                }
                catch (SQLException e1)
                {
                    e1.printStackTrace();
                }
                throw  new RuntimeException(e.getMessage());
            }finally
            {
                close(rs,ps,ct);
            }
    
        }
    
        //先写一个update、delete、insert
        //sql格式：update 表名 set 字段名 =？where 字段=？
        //parameter神应该是（”abc“,23）
        public static void executeUpdate(String sql,String[] parameters)
        {
            try
            {
                ct=getConnection();
                ps = ct.prepareStatement(sql);
                if(parameters!=null)
                {
                    for(int i=0;i<parameters.length;i++)
                    {
                        ps.setString(i+1,parameters[i]);
                    }
    
                }
                ps.executeUpdate();
            }
            catch(Exception e)
            {
                e.printStackTrace();//开发阶段
                //抛出异常
                //可以处理，也可以不处理
                throw new RuntimeException(e.getMessage());
            }
            finally
            {
                close(rs,ps,ct);
            }
        }
    
        public static void close(ResultSet rs,Statement ps,Connection ct)
        {
            //关闭资源(先开后关)
            if(rs!=null)
            {
                try
                {
                    rs.close();
                }
                catch(SQLException e)
                {
                    e.printStackTrace();
                }
                rs=null;
            }
            if(ps!=null)
            {
                try
                {
                    ps.close();
                }
                catch(SQLException e)
                {
                    e.printStackTrace();
                }
                ps=null;
            }
            if(null!=ct)
            {
                try
                {
                    ct.close();
                }
                catch(SQLException e)
                {
                    e.printStackTrace();
                }
                ct=null;
            }
        }
    }

*  DateUtil.java

package com.xforce.utils;
    
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    
    public class DateUtil { 
    
        public static String StringToDate(Date date) {
            SimpleDateFormat sdf = null;
            try {
                sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }  
            return sdf.format(date);
        }
    }

*  Login.java

package com.xforce.controller;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.xfoce.domain.User;
    import com.xforce.service.UserService;
    @WebServlet({
       "/login"})
    public class Login extends HttpServlet { 
    
    
        public void destroy() {
            super.destroy(); // Just puts "destroy" string in log
            // Put your code here
        }
    
    
        public void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
    
        }
    
    
        public void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            String username = request.getParameter("username");
            String password = request.getParameter("password");
            User user = new User();
            user.setUsername(username);
            user.setPassword(password);
            UserService userService = new UserService();
            user = userService.checkUser(user);
            if(user != null) {
                request.setAttribute("user", user);
                request.getRequestDispatcher("/WEB-INF/main.jsp").forward(request, response);
            }
            else {
                request.setAttribute("message", "账号或密码有误！");
                request.getRequestDispatcher("/index.jsp").forward(request, response);
            }
        }
    
    
        public void init() throws ServletException {
            // Put your code here
        }
    
    }

*  web.xml

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" version="3.0">
    
        <welcome-file-list>
            <welcome-file>/index.jsp</welcome-file>
        </welcome-file-list>
    
    </web-app>

*  pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
      <modelVersion>4.0.0</modelVersion>
      <groupId>Attendance</groupId>
      <artifactId>Attendance</artifactId>
      <version>0.0.1-SNAPSHOT</version>
      <packaging>war</packaging>
      <name>Attendance</name>
      <description/>
      <properties>
            <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        </properties>
    
        <dependencies>
            <dependency>
                <groupId>javax.servlet</groupId>
                <artifactId>javax.servlet-api</artifactId>
                <version>3.1.0</version>
                <scope>provided</scope>
            </dependency>
    
         <dependency>
          <groupId>jstl</groupId>
          <artifactId>jstl</artifactId>
          <version>1.2</version>
        </dependency>
    
            
          <dependency>
          <groupId>mysql</groupId>
          <artifactId>mysql-connector-java</artifactId>
          <version>5.1.29</version>
        </dependency>
    
            <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>4.11</version>
          <scope>test</scope>
        </dependency>
    
        </dependencies>
    
        <build>
            <sourceDirectory>src/main/java</sourceDirectory>
    
            <plugins>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-war-plugin</artifactId>
                    <version>2.3</version>
                    <configuration>
                        <warSourceDirectory>src/main/webapp</warSourceDirectory>
                    </configuration>
                </plugin>
                <plugin>
                    <groupId>org.apache.maven.plugins</groupId>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <version>3.1</version>
                    <configuration>
                        <source>1.7</source>
                        <target>1.7</target>
                    </configuration>
                </plugin>
            </plugins>
        </build>
    </project>

### **效果** ###

![这里写图片描述][SouthEast 3]

[SouthEast]: /images/20220610/4126583479e34277b896663aca0bdab9.png
[SouthEast 1]: /images/20220610/0cb3ed6815ea419c8b9a1fd6d4b00c03.png
[SouthEast 2]: /images/20220610/4c5e5db3443640e8a25de383073d62d3.png
[SouthEast 3]: /images/20220610/d408c4faeb4948999eb0f6fd76aec090.png