Mybatis关联关系配置（一对一、多对一）
BlogMapper.xml<?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.cj.dao.BlogDao"><!-- 定义Blog的resultMap。id值用于标识resultMap，type值为resultMap的结果类型 --> <resultMap type="Blog" id="Blogresult"> <!-- 基本数据类型映射。column为数据库的列，property为该列所对应的Java属性 --> <id column="id" property="id"/> <result column="title" property="title"/> <result column="content" property="content"/> <result column="createTime" property="createTime"/> <!-- 配置关联对象。其中： property属性值为当前Blog对象的关联对象名； javaType属性值为关联对象属性所属的完全限定类名或别名； select属性值为所请求的select映射的ID，该select使用子查询获取其所关联的属性对象； column属性值为传给子查询的字段，即外键列 --> <association property="author" javaType="Author" select="getAuthor" column="author_id"/> </resultMap> <select id="getAuthor" parameterType="int" resultType="Author"> select *from Author where id = #{id} </select> <select id="getBlog" parameterType="int" resultMap="Blogresult"> select * from blog where id = #{id} </select></mapper>
BlogDao
package com.cj.dao;import com.cj.entity.Author;import com.cj.entity.Blog;public interface BlogDao { //根据博客id查询信息 public Blog getBlog(int id); //根据作者id查询作者信息 public Author getAuthor(int id);}Blog实体类package com.cj.entity;import java.util.Date;public class Blog { private int id; private String title; private String content; private Date createTime; private Author author; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getTitle() { return title; } public void setTitle(String title) { this.title = title; } public String getContent() { return content; } public void setContent(String content) { this.content = content; } public Date getCreateTime() { return createTime; } public void setCreateTime(Date createTime) { this.createTime = createTime; } public Author getAuthor() { return author; } public void setAuthor(Author author) { this.author = author; } public Blog() { super(); // TODO Auto-generated constructor stub } public Blog(String title, String content, Date createTime, Author author) { super(); this.title = title; this.content = content; this.createTime = createTime; this.author = author; }}
1、gis空间分析案例_7参数单坐标转换
2、浅谈Generator和Promise原理及实现
3、用文本编辑器打开文本文件
4、戏谈单向链表判环
5、maven仓库
test测试类
public static void main(String[] args) throws Exception { SqlSession openSession = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("config.xml")).openSession(); BlogDao mapper = openSession.getMapper(BlogDao.class); //根据博客id查询信息（包含作者） Blog blog = mapper.getBlog(1); System.out.println(blog.getTitle()); System.out.println(blog.getAuthor().getUsername()); } 优质内容筛选与推荐>>1、gis空间分析案例_7参数单坐标转换
2、浅谈Generator和Promise原理及实现
3、用文本编辑器打开文本文件
4、戏谈单向链表判环
5、maven仓库