day09---（03）课程发布-课程信息确认

一、功能分析

二、多表链接查询的sql语句

#多表关联查询
#内链接 A inner join B on A.id = B.id
#左外链接 A left join B on Aid=B.id
#右外链接 A right join B on Aid=B.id

SELECT ec.title,et.name,
es1.title AS oneSubject,es2.title AS twoSubject
FROM edu_course ec
LEFT JOIN edu_teacher et ON ec.teacher_id = et.id
LEFT JOIN edu_subject es1 ON ec.subject_parent_id = es1.id
LEFT JOIN edu_subject es2 ON ec.subject_id = es2.id
WHERE ec.id = ‘1275627083367833602’;

三、编写接口、根据课程id查询课程信息

（1）建立CoursePublishVo类封装数据

package com.atguigu.eduservice.entity.vo;
import io.swagger.annotations.ApiModel;
import lombok.Data;
import java.io.Serializable;
@ApiModel(value = "课程发布信息")
@Data
public class CoursePublishVo  implements Serializable {
    private static final long serialVersionUID = 1L;

    private String title;
    private String cover;
    private Integer lessonNum;
    private String subjectLevelOne;
    private String subjectLevelTwo;
    private String teacherName;
    private String price;//只用于显示
}

（2）在EduCourseController添加根据课程id查询课程发布信息的方法

@ApiOperation(value = "根据课程id查询课程发布信息")
@GetMapping("getCoursePublishVoById/{courseId}")
public R getCoursePublishVoById(@PathVariable String courseId){
    CoursePublishVo coursePublishVo =
            courseService.getCoursePublishVo(courseId);
    return R.ok().data("coursePublishVo",coursePublishVo);
}

（3）在EduCourseService添加根据课程id查询课程发布信息的接口

CoursePublishVo getCoursePublishVo(String courseId);

（4）在EduCourseServiceImpl实现根据课程id查询课程发布信息的接口方法

//根据课程id查询课程发布信息
@Override
public CoursePublishVo getCoursePublishVo(String id) {
    CoursePublishVo coursePublishVo = baseMapper.getCoursePublishVo(id);
    return coursePublishVo;
}

（5）在EduCourseMapper添加getCoursePublishVo方法

public interface EduCourseMapper extends BaseMapper<EduCourse> {
    CoursePublishVo getCoursePublishVo(String id);
}

（6）在EduCourseMapper.xml实现getCoursePublishVo方法

<?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.atguigu.eduservice.mapper.EduCourseMapper">
            <select id="getCoursePublishVo" resultType="com.atguigu.eduservice.entity.vo.CoursePublishVo">
        SELECT ec.id,ec.title,ec.cover,
        ec.lesson_num AS lessonNum,ec.price,
        et.name AS teacherName,
        es1.title AS subjectLevelOne,es2.title AS subjectLevelTwo
        FROM edu_course ec
        LEFT JOIN edu_teacher et ON ec.teacher_id = et.id
        LEFT JOIN edu_subject es1 ON ec.subject_parent_id = es1.id
        LEFT JOIN edu_subject es2 ON ec.subject_id = es2.id
        WHERE ec.id = #{id}
            </select>

</mapper>

四、测试接口

（1）报如下错误：

org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.atguigu.eduservice.mapper.EduCourseMapper.getCoursePublishVo

（1）问题定位：
maven加载机制：在默认状况下，只会把src-main-java文件夹中的java类型文件加载，其余类型无论了，xml文件没有加载，因此报错
输出文件里没有mapper信息：

（2）解决方案：经过配置，让maven加载配置文件

1）在service模块中修改pom.xml进行配置

<!-- 项目打包时会将java目录中的*.xml文件也进行打包 -->
<build>
    <resources>
        <resource>
            <directory>src/main/java</directory>
            <includes>
                <include>**/*.xml</include> </includes> <filtering>false</filtering> </resource> </resources> </build> 

2）在当前模块中进行配置

#配置mapper xml文件的路径
mybatis-plus.mapper-locations=classpath:com/atguigu/eduservice/mapper/xml/*.xml 

五、前端整合

（1）在api/course.js中添加接口方法

//根据课程id查询课程发布信息
getCoursePublishVoById(courseId){
  return request({
    url: `/eduservice/educourse/getCoursePublishVoById/${courseId}`,
    method: 'get'
  })
}

（2）页面元素实现

<template>
  <div class="app-container">
    <h2 style="text-align: center;">发布新课程</h2>
    <el-steps :active="3" process-status="wait" align-center style="margin-bottom: 40px;">
      <el-step title="填写课程基本信息"/>
      <el-step title="建立课程大纲"/>
      <el-step title="发布课程"/>
    </el-steps>
    <div class="ccInfo">
      <img :src="coursePublish.cover">
      <div class="main">
        <h2>{{ coursePublish.title }}</h2>
        <p class="gray"><span>共{{ coursePublish.lessonNum }}课时</span></p>
        <p><span>所属分类：{{ coursePublish.subjectLevelOne }} — {{ coursePublish.subjectLevelTwo }}</span></p>
        <p>课程讲师：{{ coursePublish.teacherName }}</p>
        <h3 class="red">￥{{ coursePublish.price }}</h3>
      </div>
    </div>
    <div>
      <el-button @click="previous">返回修改</el-button>
      <el-button :disabled="saveBtnDisabled" type="primary" @click="publish">发布课程</el-button>
    </div>
  </div>
</template>

（3）在course/publish.vue中实现js方法

在课程大纲页面，修改客户发布页面入口

import publish from "@/api/publish";
export default {
  data() {
    return {
      courseId: "",
      coursePublish:{},//课程发布信息
      saveBtnDisabled: false // 保存按钮是否禁用
    }
  },

  created() {
    console.log('publish created')
    if (this.$route.params && this.$route.params.id) {
      this.courseId = this.$route.params.id;
      console.log("this.courseId=" + this.courseId);
      //根据课程id查询课程发布信息
      publish.getCoursePublishVoById(this.courseId)
      .then(response=>{
        this.coursePublish=response.data.coursePublishVo
      })
    }
  },

（4）在course/publish.vue页面底端添加页面样式

<style scoped>
.ccInfo {
    background: #f5f5f5;
    padding: 20px;
    overflow: hidden;
    border: 1px dashed #DDD;
    margin-bottom: 40px;
    position: relative;
}
.ccInfo img {
    background: #d6d6d6;
    width: 500px;
    height: 278px;
    display: block;
    float: left;
    border: none;
}
.ccInfo .main {
    margin-left: 520px;
}

.ccInfo .main h2 {
    font-size: 28px;
    margin-bottom: 30px;
    line-height: 1;
    font-weight: normal;
}
.ccInfo .main p {
    margin-bottom: 10px;
    word-wrap: break-word;
    line-height: 24px;
    max-height: 48px;
    overflow: hidden;
}

.ccInfo .main p {
    margin-bottom: 10px;
    word-wrap: break-word;
    line-height: 24px;
    max-height: 48px;
    overflow: hidden;
}
.ccInfo .main h3 {
    left: 540px;
    bottom: 20px;
    line-height: 1;
    font-size: 28px;
    color: #d32f24;
    font-weight: normal;
    position: absolute;
}
</style>

（5）发布页面展现效果