Mybatis多表連接

Mybatis多表連接

    此博文主要是記錄自己日常學習以及講述給學弟的隨堂筆記，故你可能會看不到完整的代碼，考慮到你也興趣，
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                                                                   河南濟源普普通通的追夢孩
                                                                           ——愛貓狗的小郝
                                                                             2020/05/06

前言

兩種類型

resultType和resultMap都可以完成輸出映射：

• resultType映射要求sql查詢的列名和輸出映射pojo類型的屬性名一致(不一致可以通過起別名來解決)
• resultMap映射時對sql查詢的列名和輸出映射pojo類型的屬性名作一個對應關係。(不一致也無所謂)

resultType ：直接表示返回類型
基本數據類型
複雜數據類型
resultMap ：對外部resultMap的引用
應用場景：
數據庫字段信息與對象屬性不一致
複雜的聯合查詢，自由控制映射結果
二者不能同時存在，本質上都是Map數據結構

resultMap

解決列名與實體類屬性名不一致的問題，同時解決多表連接的查詢問題。

操作步驟

• 分析需求（主查詢表、關聯查詢表）
• 編寫sql語句
• resultMap進行映射的思路，在相應的pojo里加關聯
• 編寫NewsMapper.xml
• 編寫NewsMapperr.java
• 單元測試
• 前端界面展示

resultMap映射問題

resultMap的配置

 <resultMap id="newsResultMap" type="hsy.cool.bean.News">
        <result property="id" column="id"/>
        <result property="title" column="title"/>
        <result property="content" column="content"/>
        <result property="users_id" column="users_id"/>
        <result property="category_id" column="category_id"/>
        <result property="pubtime" column="pubtime"/>
        <result property="keywords" column="keywords"/>
        <result property="state" column="state"/>
        <result property="check_users_id" column="check_users_id"/>
        <result property="check_time" column="check_time"/>
        <result property="is_elite" column="is_elite"/>
    </resultMap>

查詢

 <select id="findAllNor" resultMap="newsResultMap">
       select * from n_news
    </select>

java代碼

 List<News>findAllNor();

單元測試

@Test
    public void findAllNor(){
        NewsMapper dao= MybatisUtils.getMapper(NewsMapper.class);
        List<News> list=dao.findAllNor();
        Assert.assertNotNull(list);
        Assert.assertEquals(8,list.size());
        String time= DateUtils.parse(list.get(0).getCheck_time());
        Assert.assertEquals("2020-04-10 11:41:40",time);
    }

多表連接——簡單

通過增加簡單類型的屬性實現展⽰多表數據的⽬的

resultMap新增

 <result property="usersName" column="nickname"/>
 <result property="categoryName" column="name"/>
 <result property="checkUsersName" column="nickname"/>

實體類新增屬性

    private String usersName;
    private String categoryName;
    private String checkUsersName;
    // setter/getter

單元測試新增

 Assert.assertEquals("匿名",list.get(0).getUsersName());

多表連接——複雜

通過在實體類中添加對象的類型的屬性以及assocation標籤實現對複雜數據類型的映射

    <resultMap id="newsMapComplex" type="hsy.cool.bean.News">
        <result property="id" column="id"/>
        <result property="title" column="title"/>
        <result property="content" column="content"/>
        <result property="users_id" column="users_id"/>
        <result property="category_id" column="category_id"/>
        <result property="pubtime" column="pubtime"/>
        <result property="keywords" column="keywords"/>
        <result property="state" column="state"/>
        <result property="check_users_id" column="check_users_id"/>
        <result property="check_time" column="check_time"/>
        <result property="is_elite" column="is_elite"/>
        <result property="categoryName" column="name"/>
        <result property="checkUsersName" column="nickname"/>
        <association property="own" javaType="hsy.cool.bean.Users">
            <result property="id" column="id"/>
            <result property="nickname" column="nickname"/>
            <result property="realname" column="realname"/>
            <result property="phone" column="phone"/>
            <result property="email" column="email"/>
            <result property="address" column="address"/>
            <result property="createTime" column="create_time"/>
        </association>
    </resultMap>

查詢

 <select id="findAllComplex" resultMap="newsMapComplex">
       select
         n.id,
         title,
         content,
         users_id,
         category_id,
         c.name,
         pubtime,
         keywords,
         state,
         check_users_id,
         u1.nickname,
         check_time,
         is_elite,
         u.*
        from n_news n inner join n_users u on n.users_id=u.id
                       inner join n_category c on n.category_id=c.id
                       inner join n_users u1 on n.check_users_id=u1.id
    </select>

java代碼

  List<News>findAllComplex();

實體類新增

  private Users own;
  //setter/getter

單元測試

    @Test
    public void  findAllComplex(){
        NewsMapper dao=MybatisUtils.getMapper(NewsMapper.class);
        List<News> list=dao.findAllComplex();
        Assert.assertNotNull(list);
        Assert.assertEquals(8,list.size());
        String time= DateUtils.parse(list.get(0).getCheck_time());
        Assert.assertEquals("2020-04-10 11:41:40",time);
        Assert.assertEquals("匿名啊啊啊",list.get(0).getOwn().getNickname());
    }

JSP頁面修改

          <td class="users">${news.own.nickname}
              <div class="usersInfo">
                  <table>
                      <tr>
                          <td>賬號:</td>
                          <td>${news.own.nickname}</td>
                      </tr>

                      <tr>
                          <td>姓名:</td>
                          <td>${news.own.realname}</td>
                      </tr>

                      <tr>
                          <td>電話:</td>
                          <td>${news.own.phone}</td>
                      </tr>

                      <tr>
                          <td>郵件:</td>
                          <td>${news.own.email}</td>
                      </tr>

                      <tr>
                          <td>地址:</td>
                          <td>${news.own.address}</td>
                      </tr>
                  </table>
              </div>
          </td>

java代碼修改

List<News> list=newsDao.findAllComplex();

添加樣式

    <style type="text/css">
        .usersInfo{
            width: 200px;
            background: #eee;
        }
    </style>

樣式修改

    <style type="text/css">
        .usersInfo{
            width: 200px;
            background: #eee;
            position: absolute;
            display: none;
        }
    </style>

導入jquery

    <script type="text/javascript" src="${pageContext.request.contextPath}/js/jquery-1.8.3.min.js">
    </script>

動態樣式

    <script>
        //選擇器.動作
        $(function(){
            $(".users").hover(function(){
                $(".usersInfo",this).css("display","block");
            },function(){
                $(".usersInfo",this).css("display","none");
            });
        });
    </script>

完整頁面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>新聞列表</title>
    <style type="text/css">
        .usersInfo{
            width: 200px;
            background: #eee;
            position: absolute;
            display: none;
        }
    </style>
    <script type="text/javascript" src="${pageContext.request.contextPath}/js/jquery-1.8.3.min.js"></script>
    <script>

        $(function(){
            $(".users").hover(function(){
                $(".usersInfo",this).css("display","block");
            },function(){
                $(".usersInfo",this).css("display","none");
            });
        });
    </script>
</head>
<body>
<p>首頁/新聞</p>
<h1>新聞列表</h1>
  <table width="1000" border="1">
      <tr>
          <th>編號</th>
          <th>標題</th>
          <th>內容</th>
          <th>分類</th>
          <th>作者</th>
          <th>關鍵字</th>
          <th>發佈時間</th>
          <th>審批</th>
      </tr>
      <c:forEach items="${list}" var="news">
      <tr>
          <td>${news.id}</td>
          <td>${news.title}</td>
          <td>${news.content}</td>
          <td>${news.categoryName}</td>
          <td class="users">${news.own.nickname}
              <div class="usersInfo">
                  <table>
                      <tr>
                          <td>賬號:</td>
                          <td>${news.own.nickname}</td>
                      </tr>

                      <tr>
                          <td>姓名:</td>
                          <td>${news.own.realname}</td>
                      </tr>

                      <tr>
                          <td>電話:</td>
                          <td>${news.own.phone}</td>
                      </tr>

                      <tr>
                          <td>郵件:</td>
                          <td>${news.own.email}</td>
                      </tr>

                      <tr>
                          <td>地址:</td>
                          <td>${news.own.address}</td>
                      </tr>
                  </table>
              </div>
          </td>
          <td>${news.keywords}</td>
          <td>${news.pubtimeString}</td>
          <td>${news.checkUsersName}</td>
      </tr>
      </c:forEach>

  </table>
</body>
</html>

業務素材

數據庫表

/*
 Navicat Premium Data Transfer

 Source Server         : localhost
 Source Server Type    : MySQL
 Source Server Version : 80016
 Source Host           : localhost:3306
 Source Schema         : news

 Target Server Type    : MySQL
 Target Server Version : 80016
 File Encoding         : 65001

 Date: 21/02/2020 16:56:04
*/

SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;

-- ----------------------------
-- Table structure for n_access_logs
-- ----------------------------
DROP TABLE IF EXISTS `n_access_logs`;
CREATE TABLE `n_access_logs`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `ip` varchar(50) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `intime` datetime(0) DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP(0),
  `news_id` int(11) DEFAULT NULL,
  `users_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;

-- ----------------------------
-- Table structure for n_category
-- ----------------------------
DROP TABLE IF EXISTS `n_category`;
CREATE TABLE `n_category`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 7 CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of n_category
-- ----------------------------
INSERT INTO `n_category` VALUES (1, '時事');
INSERT INTO `n_category` VALUES (2, '財經');
INSERT INTO `n_category` VALUES (3, '體育');
INSERT INTO `n_category` VALUES (4, '娛樂');
INSERT INTO `n_category` VALUES (5, '科技');
INSERT INTO `n_category` VALUES (6, '旅遊');

-- ----------------------------
-- Table structure for n_news
-- ----------------------------
DROP TABLE IF EXISTS `n_news`;
CREATE TABLE `n_news`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `content` text CHARACTER SET utf8 COLLATE utf8_bin,
  `users_id` int(11) DEFAULT NULL,
  `category_id` int(11) DEFAULT NULL,
  `pubtime` datetime(0) DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP(0),
  `keywords` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `state` int(11) DEFAULT NULL COMMENT '1=新建，2=審批，3=刪除',
  `check_users_id` int(11) DEFAULT NULL,
  `check_time` datetime(0) DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP(0),
  `is_elite` int(11) DEFAULT NULL COMMENT '1=精華，0=非精華',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;

-- ----------------------------
-- Table structure for n_replys
-- ----------------------------
DROP TABLE IF EXISTS `n_replys`;
CREATE TABLE `n_replys`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `news_id` int(11) DEFAULT NULL,
  `content` varchar(1024) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `users_id` int(11) DEFAULT NULL,
  `replys_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;

-- ----------------------------
-- Table structure for n_short_replys
-- ----------------------------
DROP TABLE IF EXISTS `n_short_replys`;
CREATE TABLE `n_short_replys`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `news_id` int(11) DEFAULT NULL,
  `type` int(11) DEFAULT NULL COMMENT '1=贊，0=踩',
  `create_time` datetime(0) DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP(0),
  `users_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;

-- ----------------------------
-- Table structure for n_users
-- ----------------------------
DROP TABLE IF EXISTS `n_users`;
CREATE TABLE `n_users`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `nickname` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
  `realname` varchar(50) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `pwd` varchar(50) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `phone` varchar(20) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `email` varchar(100) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `address` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `create_time` datetime(0) DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP(0),
  `type` int(11) DEFAULT NULL COMMENT '0=管理員，1=讀者，2=編輯',
  `realid` varchar(20) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL COMMENT '身份證號',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 3 CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of n_users
-- ----------------------------
INSERT INTO `n_users` VALUES (1, '管理員', NULL, '123', NULL, NULL, NULL, '2019-10-09 10:06:39', 0, NULL);
INSERT INTO `n_users` VALUES (2, '匿名', NULL, '123', NULL, NULL, NULL, '2019-10-09 10:11:42', 1, NULL);

-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) CHARACTER SET utf8 COLLATE utf8_bin NOT NULL,
  `phone` varchar(20) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 23 CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES (1, '張三', '110');
INSERT INTO `student` VALUES (2, '李四', '120');
INSERT INTO `student` VALUES (3, '王五', '119');
INSERT INTO `student` VALUES (4, '趙六', '110');
INSERT INTO `student` VALUES (15, 'xxx', '111');
INSERT INTO `student` VALUES (16, 'xxx', '111');
INSERT INTO `student` VALUES (17, 'xxx', '111');
INSERT INTO `student` VALUES (18, 'xxx', '111');
INSERT INTO `student` VALUES (19, 'xxx', '111');
INSERT INTO `student` VALUES (20, 'xxx', '111');
INSERT INTO `student` VALUES (21, 'xxx', '111');

-- ----------------------------
-- Table structure for users
-- ----------------------------
DROP TABLE IF EXISTS `users`;
CREATE TABLE `users`  (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `pwd` varchar(50) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `phone` varchar(50) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `email` varchar(100) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  `address` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 4 CHARACTER SET = utf8 COLLATE = utf8_bin ROW_FORMAT = Dynamic;

-- ----------------------------
-- Records of users
-- ----------------------------
INSERT INTO `users` VALUES (1, '張三', '123', '110', '[email protected]', '洛陽');
INSERT INTO `users` VALUES (2, '李四', '111', '110', '[email protected]', '洛陽');
INSERT INTO `users` VALUES (3, '李四', '555', '110', '[email protected]', '洛陽');

SET FOREIGN_KEY_CHECKS = 1;

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