三层架构 —— 具体代码

一、前提概要

1. 表示层（Web）接收请求、响应数据

（1）接收请求参数

（2）调用service查询学生

（3）返回结果

2. 业务层（Service）逻辑处理

（1）调用mapper查询学生

3. 持久层（Dao）数据访问

@Select(" ")

void selectById(Integer id);

 

二、准备环境

1. 创建新的环境，引入坐标 

2. 创建包结构（ domain、util、servlet、service、mapper ）

3. 添加文件（ Mybatis配置文件、工具类、实体类 ）

4. 添加过滤器（全面处理中文乱码）

5. 添加前端页面

6. 部署测试

 

三、具体代码

（一）domain（ 实体类包 ）

package com.itheima.domain;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Student {
    private String id;  //学号
    private String name;    //姓名
    private String birthday;  //生日
    private String address; //地址
}

 

（二）mapper（ 持久层 ）

package com.itheima.mapper;

import com.itheima.domain.Student;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import java.util.List;

public interface StudentMapper {
    @Select("select * from student")
    List<Student> findAll();

    @Insert("insert into student values(#{id},#{name},#{birthday},#{address})")
    void save(Student student);

    @Delete("delete from student where id = #{id}")
    void deleteById(String id);

    @Select("select * from student where id = #{id}")
    Student findById(String id);

    @Update("update student set name = #{name}, birthday = #{birthday}, address = #{address} where id = #{id}")
    void update(Student student);
}

 

（三）service（ 业务层 ）

package com.itheima.service;

import com.itheima.domain.Student;

import java.util.List;

public interface StudentService {

    List<Student> findAll();

    void save(Student student);

    void deleteById(String id);

    Student findById(String id);

    void update(Student student);
}

　　impl

package com.itheima.service.impl;

import com.itheima.domain.Student;
import com.itheima.mapper.StudentMapper;
import com.itheima.service.StudentService;
import com.itheima.util.MyBatisUtil;
import org.apache.ibatis.session.SqlSession;

import java.util.List;

public class StudentServiceImpl implements StudentService {
    @Override
    public List<Student> findAll() {
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
        List<Student> list = studentMapper.findAll();
        MyBatisUtil.close(sqlSession);
        return list;
    }

    @Override
    public void save(Student student) {
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
        studentMapper.save(student);
        MyBatisUtil.close(sqlSession);
    }

    @Override
    public void deleteById(String id) {
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
        studentMapper.deleteById(id);
        MyBatisUtil.close(sqlSession);
    }

    @Override
    public Student findById(String id) {
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
        Student student = studentMapper.findById(id);
        MyBatisUtil.close(sqlSession);
        return student;
    }

    @Override
    public void update(Student student) {
        SqlSession sqlSession = MyBatisUtil.getSqlSession();
        StudentMapper studentMapper = sqlSession.getMapper(StudentMapper.class);
        studentMapper.update(student);
        MyBatisUtil.close(sqlSession);
    }
}

 

（四）util（ 工具类包 ）

package com.itheima.util;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.InputStream;

public class MyBatisUtil {
    private static SqlSessionFactory sqlSessionFactory;

    //静态代码块
    static {
        try {
            //读取配置文件,读成数据流
            InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");

            //创建SqlSessionFactory
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    //获取sqlSession
    public static SqlSession getSqlSession() {
        return sqlSessionFactory.openSession();
    }

    //提交事务和释放资源
    public static void close(SqlSession sqlSession) {
        if (sqlSession != null) {
            //提交事务(mybatis默认情况下是不会自动提交事务)
            sqlSession.commit();

            //释放资源
            sqlSession.close();
        }
    }
}

 

（五）web（ 表示层 ）

　　filter

package com.itheima.web.filter;
import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * 解决全站乱码问题，处理所有的请求
 */
@WebFilter("/*")
public class CharacterEncodingFilter implements Filter {
    @Override
    public void doFilter(ServletRequest req, ServletResponse rep, FilterChain filterChain) throws IOException, ServletException {
        //将父接口转为子接口
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) rep;

        //不需要过滤的url
        String path = request.getServletPath();
        String[] urls = {".html", ".js", ".css", ".ico", ".jpg", ".png"};
        boolean flag = true;
        for (String str : urls) {
            if (path.indexOf(str) != -1) {
                flag = false;
                break;
            }
        }

        //需要过滤的资源走这个逻辑
        if (flag) {
            //解决post请求中文数据乱码问题
            if (request.getMethod().equalsIgnoreCase("post")) {
                request.setCharacterEncoding("utf-8");
            }

            //解决跨域问题
            /* 允许跨域的主机地址 */
            response.setHeader("Access-Control-Allow-Origin", "*");
            /* 允许跨域的请求方法GET, POST, HEAD 等 */
            response.setHeader("Access-Control-Allow-Methods", "*");
            /* 重新预检验跨域的缓存时间 (s) */
            response.setHeader("Access-Control-Max-Age", "3600");
            /* 允许跨域的请求头 */
            response.setHeader("Access-Control-Allow-Headers", "*");
            /* 是否携带cookie */
            response.setHeader("Access-Control-Allow-Credentials", "true");


            //处理响应乱码
            response.setContentType("application/json;charset=utf-8");
        }

        filterChain.doFilter(request, response);
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }
    @Override
    public void destroy() {

    }
}

　　servlet

package com.itheima.web.servlet;

import cn.hutool.core.io.IoUtil;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.itheima.domain.Student;
import com.itheima.service.StudentService;
import com.itheima.service.impl.StudentServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.ServletInputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

@WebServlet("/studentServlet")
public class StudentServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 接收action,确定请求目的
        String action = req.getParameter("action");
        if ("findAll".equals(action)) {
            findAll(req, resp);
        } else if ("save".equals(action)) {
            save(req, resp);
        } else if ("deleteById".equals(action)) {
            deleteById(req, resp);
        } else if ("findById".equals(action)) {
            findById(req, resp);
        } else if ("update".equals(action)) {
            update(req, resp);
        } else {
            resp.getWriter().write("方法请求错误");
        }
    }

    // 修改
    private void update(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        // 1. 获取请求参数
        ServletInputStream is = req.getInputStream();
        String json = IoUtil.read(is, "utf-8");
        Student student = new ObjectMapper().readValue(json, Student.class);
        // 2. 调用业务逻辑
        StudentService studentService = new StudentServiceImpl();
        studentService.update(student);
        // 3. 响应结果
        resp.getWriter().write("OK");
    }

    // 根据id查询学生(回显)
    private void findById(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        // 1. 获取请求参数
        String id = req.getParameter("id");
        // 2. 调用业务逻辑
        StudentService studentService = new StudentServiceImpl();
        Student student = studentService.findById(id);
        // 3. 响应结果
        String json = new ObjectMapper().writeValueAsString(student);
        resp.getWriter().write(json);
    }

    // 根据id删除
    private void deleteById(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        // 1. 获取请求参数
        String id = req.getParameter("id");
        // 2. 调用业务逻辑
        StudentService studentService = new StudentServiceImpl();
        studentService.deleteById(id);
        // 3. 响应结果
        resp.getWriter().write("OK");

    }

    // 新增
    private void save(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        // 1. 获取请求参数(如果页面提交的数据为json格式,则req.getPXXX方法不能用了,只能使用字节流获取)
//        String id = req.getParameter("id");
        ServletInputStream is = req.getInputStream();
        // 把字节数据转换为指定编码格式的字符串{key:value}
        String json = IoUtil.read(is, "utf-8");
        Student student = new ObjectMapper().readValue(json, Student.class);
        // 2. 调用业务逻辑
        StudentService studentService = new StudentServiceImpl();
        studentService.save(student);
        // 3. 响应结果
        resp.getWriter().write("OK");
    }

    // 查询所有
    private void findAll(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        // 1. 获取请求参数(无)

        // 2. 调用业务逻辑
        StudentService studentService = new StudentServiceImpl();
        List<Student> studentList = studentService.findAll();
        // 3. 响应结果
        String json = new ObjectMapper().writeValueAsString(studentList);
        resp.getWriter().write(json);
    }
}

 

四、配置

（一）pom.xml

    <dependencies>
        <!--数据库驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>
        <!--mybatis框架-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.9</version>
        </dependency>
        <!--lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.26</version>
        </dependency>
        <!--json转换工具-->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.9.9</version>
        </dependency>
        <!--单元测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>

        <!--hutool-->
        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>5.4.3</version>
        </dependency>
        <!--servlet-->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>3.0.1</version>
        </dependency>
    </dependencies>
    
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>3.2.2</version>
            </plugin>
        </plugins>
    </build>

 

（二）resources

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    
    <!--配置-->
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <!--数据库环境配置-->
    <environments default="mysql">
        <environment id="mysql">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/vue"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>

    <!--映射关系配置-->
    <mappers>
        <package name="com.itheima.mapper"></package>
    </mappers>
</configuration>