DAO 层实现

Posted 2020-09-24 专注it

一、实验介绍

1.1 实验内容

本节课程主要利用 MyBatis 框架实现 DAO 层。

1.2 实验知识点

• MyBatis 框架
• mysql

1.3 实验环境

• JDK1.8
• Eclipse JavaEE

二、实验步骤

根据第一节，我们可以知道系统的功能包括了哪些，根据第三节和第四节，我们知道了数据库表的结构和持久化实体，因此，在这里我们完成数据库的访问操作。

首先在项目 hrms 的 Java Resources 目录的 src/main/java 下新建包 com.shiyanlou.dao，作为 DAO 层的包， 并在 src/main/resources 下新建一个 Folder mappers 用来放置 MyBatis 的 mapper.xml 文件。

2.1 MyBatis 配置文件

在目录 src/main/resources 下新建 MyBatis 配置文件 mybatis-config.xml ，在这里主要配置了为 JavaBean 取别名，代码如下：

<?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>
    <!-- 为JavaBean 起类别名 -->
    <typeAliases>
        <package name="com.shiyanlou.domain" />
    </typeAliases> 
</configuration>

注：在这里，我们没有配置 MyBatis 的运行环境、数据源等，那是因为我们要将这些交给 Spring 进行配置管理。

2.2 AdminDao 接口

在包 com.shiyanlou.dao 下建一个 AdminDao.java 接口文件，代码如下：

package com.shiyanlou.dao;

import java.util.List;
import java.util.Map;

import org.springframework.stereotype.Repository;

import com.shiyanlou.domain.Admin;

@Repository
public interface AdminDao {

    /** 登录
     * 
     * @param admin
     * @return
     */
    public Admin login(Admin admin);

    /** 根据条件查询管理员
     * 
     * @param map
     * @return
     */
    public List<Admin> findAdmins(Map<String, Object> map);

    /** 根据条件查询管理员人数
     * 
     * @param map
     * @return
     */
    public Integer getCount(Map<String, Object> map);

    /** 添加管理员
     * 
     * @param admin
     * @return
     */
    public Integer addAdmin(Admin admin);

    /** 修改管理员
     * 
     * @param admin
     * @return
     */
    public Integer updateAdmin(Admin admin);

    /** 删除管理员
     * 
     * @param id
     * @return
     */
    public Integer deleteAdmin(Integer id);
}

接着在 src/main/resources/mappers 路径下新建与 AdminDao 接口对应的映射文件 AdminMapper.xml，代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.shiyanlou.dao.AdminDao">
    <!-- 自定义结果集 -->
    <resultMap type="Admin" id="AdminResult">
        <id property="id" column="admin_id" />
        <result property="username" column="username" />
        <result property="password" column="password" />
        <result property="role_name" column="role_name" />
    </resultMap>
    <!-- 登录 -->
    <select id="login" parameterType="Admin" resultMap="AdminResult">
        select * from
        admin_tb where username=#{username} and password=#{password} limit 1
    </select>
    <!-- 根据条件查询管理员 -->
    <select id="findAdmins" parameterType="Map" resultMap="AdminResult">
        select * from admin_tb
        <where>
            <if test="username!=null and username!=‘‘ ">
                username like #{username}
            </if>
        </where>
    </select>
    <!-- 根据条件查询管理员的人数 -->
    <select id="getCount" parameterType="Map" resultType="Integer">
        select count(*) from admin_tb
        <where>
            <if test="username!=null and username!=‘‘ ">
                username like #{username}
            </if>
        </where>
    </select>
    <!-- 添加管理员 -->
    <insert id="addAdmin" useGeneratedKeys="true" keyProperty="admin_id">
        insert into admin_tb(username,password)
        values(#{username},#{password})
    </insert>
    <!-- 修改管理员 -->
    <update id="updateAdmin" parameterType="Admin">
        update admin_tb set
        username=#{username},password=#{password} where admin_id=#{id}
    </update>
    <!-- 删除管理员 -->
    <delete id="deleteAdmin" parameterType="Integer">
        delete from admin_tb where
        admin_id=#{id}
    </delete>
</mapper>

2.3 PostDao 接口

在包 com.shiyanlou.dao 下建一个 PostDao.java 接口文件，代码如下：

package com.shiyanlou.dao;

import java.util.List;
import java.util.Map;

import org.springframework.stereotype.Repository;

import com.shiyanlou.domain.Post;

@Repository
public interface PostDao {

    /** 根据条件查询公告
     * 
     * @return
     */
    public List<Post>findPosts(Map<String, Object> map);

    /** 根据条件查询公告数量
     * 
     * @param map
     * @return
     */
    public Integer getCount(Map<String, Object> map);

    /** 添加公告
     * 
     * @param post
     * @return
     */    
    public Integer addPost(Post post);

    /** 修改公告
     * 
     * @param post
     * @return
     */
    public Integer updatePost(Post post);

    /** 删除公告
     * 
     * @param id
     * @return
     */
    public Integer deletePost(Integer id);

    /** 根据 ID 查询公告信息
     * 
     * @param id
     * @return
     */
    public Post getPostById(Integer id);
}

接着在 src/main/resources/mappers 路径下新建与 PostDao 接口对应的映射文件 PostMapper.xml，代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.shiyanlou.dao.PostDao">
    <!-- 自定义结果集 -->
    <resultMap type="Post" id="PostResult">
        <id property="id" column="post_id" />
        <result property="title" column="title" />
        <result property="content" column="content" />
        <result property="date" column="create_date" />
        <association property="admin" javaType="Admin">
            <id property="id" column="admin_id" />
            <result property="username" column="username" />
        </association>
    </resultMap>
    <!-- 根据条件查询公告 -->
    <select id="findPosts" parameterType="Map" resultMap="PostResult">
        select a.admin_id,a.username,p.post_id,p.title,p.content,p.create_date
        from admin_tb a,post_tb p where p.admin_id = a.admin_id
        <if test="title!=null and title!=‘‘ ">
            and p.title like #{title}
        </if>
    </select>
    <!-- 根据条件查询公告数量 -->
    <select id="getCount" parameterType="Map" resultType="Integer">
        select count(*) from post_tb
        <where>
            <if test="title!=null and title!=‘‘ ">
                title like #{title}
            </if>
        </where>
    </select>
    <!-- 添加公告 -->
    <insert id="addPost" useGeneratedKeys="true" keyProperty="post_id">
        insert
        into post_tb(title,content,admin_id,create_date)
        values(#{title},#{content},#{admin.id},#{date})
    </insert>
    <!-- 修改公告 -->
    <update id="updatePost" parameterType="Post">
        update post_tb set
        title=#{title},content=#{content},admin_id=#{admin.id},create_date=#{date}
        where post_id=#{id}
    </update>
    <!-- 删除公告 -->
    <delete id="deletePost" parameterType="Integer">
        delete from post_tb
        where
        post_id=#{id}
    </delete>
    <!-- 根据 ID 查询公告信息 -->
    <select id="getPostById" parameterType="Integer" resultMap="PostResult">
        select a.admin_id,a.username,p.post_id,p.title,p.content,p.create_date
        from admin_tb a,post_tb p where p.admin_id = a.admin_id and
        p.post_id=#{id}
    </select>
</mapper>

2.4 DepartmentDao 接口

在包 com.shiyanlou.dao 下建一个 DepartmentDao.java 接口文件，代码如下：

package com.shiyanlou.dao;

import java.util.List;
import java.util.Map;

import org.springframework.stereotype.Repository;

import com.shiyanlou.domain.Department;

@Repository
public interface DepartmentDao {

    /** 根据条件查询部门
     * 
     * @param map
     * @return
     */
    public List<Department> findDepartments(Map<String, Object> map);

    /** 根据条件查询部门数量
     * 
     * @param map
     * @return
     */
    public Integer getCount(Map<String, Object> map);

    /** 添加部门
     * 
     * @param department
     * @return
     */
    public Integer addDepartment(Department department);

    /** 修改部门
     * 
     * @param department
     * @return
     */
    public Integer updateDepartment(Department department);

    /** 删除部门
     * 
     * @param id
     * @return
     */
    public Integer deleteDepartment(Integer id);    

}

接着在 src/main/resources/mappers 路径下新建与 DepartmentDao 接口对应的映射文件 DepartmentMapper.xml，代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.shiyanlou.dao.DepartmentDao">
    <!-- 自定义结果集 -->
    <resultMap type="Department" id="DepartmentResult">
        <id property="id" column="dept_id" />
        <result property="name" column="dept_name" />
        <result property="description" column="dept_description" />
    </resultMap>
    <!-- 根据条件查询部门 -->
    <select id="findDepartments" parameterType="Map" resultMap="DepartmentResult">
        select * from dept_tb
        <where>
            <if test="name!=null and name!=‘‘ ">
                dept_name like #{name}
            </if>
        </where>
    </select>
    <!-- 根据条件查询部门数量 -->
    <select id="getCount" parameterType="Map" resultType="Integer">
        select count(*) from dept_tb
        <where>
            <if test="name!=null and name!=‘‘ ">
                dept_name like #{name}
            </if>
        </where>
    </select>
    <!-- 添加部门 -->
    <insert id="addDepartment" useGeneratedKeys="true" keyProperty="dept_id">
        insert into dept_tb(dept_name,dept_description)
        values(#{name},#{description})
    </insert>
    <!-- 修改部门 -->
    <update id="updateDepartment" parameterType="Department">
        update dept_tb set
        dept_name=#{name},dept_description=#{description} where dept_id=#{id}
    </update>
    <!-- 删除部门 -->
    <delete id="deleteDepartment" parameterType="Integer">
        delete from dept_tb where
        dept_id=#{id}
    </delete>
</mapper>

2.5 PositionDao 接口

在包 com.shiyanlou.dao 下建一个 PositionDao.java 接口文件，代码如下：

package com.shiyanlou.dao;

import java.util.List;
import java.util.Map;

import org.springframework.stereotype.Repository;

import com.shiyanlou.domain.Position;

@Repository
public interface PositionDao {

    /** 根据条件查询职位
     * 
     * @param map
     * @return
     */
    public List<Position> findPositions(Map<String, Object> map);

    /** 根据条件查询职位数量
     * 
     * @param map
     * @return
     */
    public Integer getCount(Map<String, Object> map);

    /** 添加职位
     * 
     * @param position
     * @return
     */
    public Integer addPosition(Position position);

    /** 修改职位
     * 
     * @param position
     * @return
     */
    public Integer updatePosition(Position position);

    /** 删除职位
     * 
     * @param id
     * @return
     */
    public Integer deletePosition(Integer id);
}

接着在 src/main/resources/mappers 路径下新建与 PositionDao 接口对应的映射文件 PositionMapper.xml，代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.shiyanlou.dao.PositionDao">
    <!-- 自定义结果集 -->
    <resultMap type="Position" id="PositionResult">
        <id property="id" column="pos_id" />
        <result property="name" column="pos_name" />
        <result property="description" column="pos_description" />
    </resultMap>
    <!-- 根据条件查询职位 -->
    <select id="findPositions" parameterType="Map" resultMap="PositionResult">
        select * from position_tb
        <where>
            <if test="name!=null and name!=‘‘ ">
                pos_name like #{name}
            </if>
        </where>
    </select>
    <!-- 根据条件查询职位数量 -->
    <select id="getCount" parameterType="Map" resultType="Integer">
        select count(*) from position_tb
        <where>
            <if test="name!=null and name!=‘‘ ">
                pos_name like #{name}
            </if>
        </where>
    </select>
    <!-- 添加职位 -->
    <insert id="addPosition" useGeneratedKeys="true" keyProperty="pos_id">
        insert into position_tb(pos_name,pos_description)
        values(#{name},#{description})
    </insert>
    <!-- 修改职位 -->
    <update id="updatePosition" parameterType="Position">
        update position_tb set
        pos_name=#{name},pos_description=#{description} where pos_id=#{id}
    </update>
    <!-- 删除职位 -->
    <delete id="deletePosition" parameterType="Integer">
        delete from position_tb where
        pos_id=#{id}
    </delete>
</mapper>

2.6 EmployeeDao 接口

在包 com.shiyanlou.dao 下建一个 EmployeeDao.java 接口文件，代码如下：

package com.shiyanlou.dao;

import java.util.List;
import java.util.Map;

import org.springframework.stereotype.Repository;

import com.shiyanlou.domain.Employee;
import com.shiyanlou.domain.Post;

@Repository
public interface EmployeeDao {

    /** 根据条件查询员工
     * 
     * @param map
     * @return
     */
    public List<Post>findEmployees(Map<String, Object> map);

    /** 根据条件查询员工数量
     * 
     * @param map
     * @return
     */
    public Integer getCount(Map<String, Object> map);

    /** 添加员工
     * 
     * @param employee
     * @return
     */
    public Integer addEmployee(Employee employee);

    /** 修改员工
     * 
     * @param employee
     * @return
     */
    public Integer updateEmployee(Employee employee);

    /** 删除员工
     * 
     * @param id
     * @return
     */
    public Integer deleteEmployee(String id);
}

接着在 src/main/resources/mappers 路径下新建与 EmployeeDao 接口对应的映射文件 EmployeeMapper.xml，代码如下：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.shiyanlou.dao.EmployeeDao">
    <!-- 自定义结果集 -->
    <resultMap type="Employee" id="EmployeeResult">
        <id property="id" column="emp_id" />
        <result property="name" column="emp_name" />
        <result property="sex" column="sex" />
        <result property="phone" column="phone" />
        <result property="email" column="email" />
        <result property="address" column="address" />
        <result property="education" column="education" />
        <result property="birthday" column="birthday" />
        <!-- 关联映射：association -->
        <association property="department" javaType="Department">
            <id property="id" column="dept_id" />
            <result property="name" column="dept_name" />
        </association>
        <association property="position" javaType="Position">
            <id property="id" column="pos_id" />
            <result property="name" column="pos_name" />
        </association>
    </resultMap>
    <!-- 根据条件查询员工 -->
    <select id="findEmployees" parameterType="Map" resultMap="EmployeeResult">
        select e.emp_id,e.emp_name,e.sex,e.phone,e.email,e.address,e.education,e.birthday,d.dept_id,d.dept_name,p.pos_id,p.pos_name
        from employee_tb e,dept_tb d,position_tb p where e.dept_id = d.dept_id
        and e.pos_id = p.pos_id
        <if test="id!=null and id!=‘‘ ">
            and e.emp_id like #{id}
        </if>
        <if test="name!=null and name!=‘‘ ">
            and e.emp_name like #{name}
        </if>
        <if test="department_name!=null and department_name!=‘‘ ">
            and d.dept_name like #{department_name}
        </if>
        <if test="position_name!=null and position_name!=‘‘ ">
            and p.pos_name like #{position_name}
        </if>
        <if test="sex!=null and sex!=‘‘ ">
            and e.sex like #{sex}
        </if>
    </select>
    <!-- 根据条件查询员工人数 -->
    <select id="getCount" parameterType="Map" resultType="Integer">
        select count(*) from employee_tb e,dept_tb d,position_tb p where
        e.dept_id = d.dept_id
        and e.pos_id = p.pos_id
        <if test="id!=null and id!=‘‘ ">
            and e.emp_id like #{id}
        </if>
        <if test="name!=null and name!=‘‘ ">
            and e.emp_name like #{name}
        </if>
        <if test="sex!=null and sex!=‘‘ ">
            and e.sex like #{sex}
        </if>
    </select>
    <!-- 添加员工 -->
    <insert id="addEmployee" parameterType="Employee">
        insert
        into employee_tb(emp_id,emp_name,sex,phone,email,address,education,birthday,dept_id,pos_id)
        values(#{id},#{name},#{sex},#{phone},#{email},#{address},#{education},#{birthday},#{department.id},#{position.id})
    </insert>
    <!-- 修改员工 -->
    <update id="updateEmployee" parameterType="Employee">
        update employee_tb set
        emp_name=#{name},sex=#{sex},phone=#{phone},email=#{email},address=#{address},education=#{education},birthday=#{birthday},dept_id=#{department.id},pos_id=#{position.id}
        where emp_id=#{id}
    </update>
    <!-- 删除员工 -->
    <delete id="deleteEmployee" parameterType="String">
        delete from employee_tb
        where
        emp_id=#{id}
    </delete>

</mapper>

三、实验总结

到这里我们就完成了 DAO 层的代码实现，下一节我们将进入 Service 层的实现。