总结在先：
①首先根据每张表创建相对应的实体类，该实体类中的属性与表中的字段名相同；
②由于每张表都需要一些增删改查的方法，因此需要创建Mapper接口（每张表各一个），接口中放有对应表的增删改查方法。
③由于是接口，只提供了方法名，本身没有具体方法的实现。因此创建对应的XxxMapper.xml文件，在该xml文件中编写相应Mapper接口方法的SQL语句。
④直接去调用Mapper接口中的方法，不方便进行管理。因此为每个Mapper接口再创建对应的Service类，通过Service类去调用Mapper接口中相应的增删改查方法，Mapper接口又会去调用相应mapper.xml文件中真正的SQL语句。
这便是整个流程。
1. 创建项目
① new Project - Spring Initailizr
②填写 Group: com.nowcoder.mycommunity
③勾选：
?- 选择Web - 勾选Spring Web
?- 选择SQL - 勾选MyBatis Framework
?- 选择NoSQL - 勾选Spring Data Redis
?- Next - Finish
2. 添加依赖：pom.xml
由于刚才勾选了一些组件，因此会自动引入对应的依赖。
我们再添加一些其他的依赖，分别为：
????????thymeleaf、test、mysql、devtools（方便我们在线build项目）
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<!--<version>5.1.49</version>-->
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
<optional>true</optional>
</dependency>3. 核心配置文件 application.properties
配置数据库连接、mybatis的一些设置。
spring.datasource.url=jdbc:mysql://localhost:3306/community
spring.datasource.username=root
spring.datasource.password=1472
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
# MyBatisProperties
mybatis.mapper-locations=classpath:mapper/*.xml
mybatis.type-aliases-package=com.nowcoder.mycommunity.entity
mybatis.configuration.use-generated-keys=true
mybatis.configuration.map-underscore-to-camel-case=true4. 创建实体类 entity
右键com.nowcoder.mycommunity新建三个实体类，起名为：entity.XXX：
①DiscussPost
该实体类对应数据库中的discuss_post表。
package com.nowcoder.mycommunity.entity;
import java.util.Date;
//对应数据库中的discuss_post表
public class DiscussPost {
private int id;
private int userId;
private String title;
private String content;
private int type; //帖子类型
private int status; //帖子状态：正常、拉黑
private Date createTime;
private int commentCount; //评论数量
private double score; //帖子得分
//get()、set()
//toString()
}
②User
该实体类对应于User表。
package com.nowcoder.mycommunity.entity;
import java.util.Date;
//对应数据库中的user表
public class User {
private int id;
private String username;
private String password;
private String salt;
private String email;
private int type;
private int statue;
private String activationCode;
private String headerUrl;
private Date createTime;
//get()、set()
//toString()
}③Page
该实体类对应于后面的分类功能。
由于分类功能需要进行数据的处理，直接将许多方法、参数封装到此类中。
package com.nowcoder.mycommunity.entity;
// 封装分页相关的信息
public class Page {
//当前页码
private int current = 1; //默认为第一页
//显示上限
private int limit = 5;
//数据总数(用于计算总页数)
private int rows;
//查询路径(用于复用分页链接)
private String path;
public int getCurrent() {
return current;
}
public void setCurrent(int current) {
//进行一些判断,免得输入一些不合理的数
if(current >= 1){
this.current = current;
}
}
public int getLimit() {
return limit;
}
public void setLimit(int limit) {
if(limit >= 1 && limit <= 100){
this.limit = limit;
}
}
public int getRows() {
return rows;
}
public void setRows(int rows) {
if(rows >= 0){
this.rows = rows;
}
}
public String getPath() {
return path;
}
public void setPath(String path) {
this.path = path;
}
//额外的方法
//获取当前页的起始行
public int getoffset(){
//计算公式为: current * limit - limit
return (current - 1) * limit;
}
//获取总页数
public int getTotal(){
if(rows % limit == 0){ //可以整除
return rows/limit;
}else {
return rows/limit + 1;
}
}
//获取展示的起始页码
public int getFrom(){
int from = current - 2; //展示前后两页
//如果前面没有两页,则展示的起始页码为1,有两页及以上,则展示的起始页码为2
return from < 1 ? 1 :from;
}
//获取展示的终止页码
public int getTo(){
int to = current + 2;
int total = getTotal();
//展示的终止页大于总页数,则展示到总页数,否则展示到to
return to > total ? total : to;
}
}
注：该类中有一些get()、set()方法需要合理设置，里面添加了一些条件。
5. 创建Mapper
右键com.nowcoder.mycommunity新建两个接口，起名为：dao.XxxMapper：
Mapper主要是对应于SQL语句的一些增删改查的方法。
刚才每个实体类都对应了一张表，我们自然需要对每张表都编写一些增删改查的方法，因此与表对应的每个实体类都需要创建对应的Mapper方法。
①DiscussPostMapper
import org.apache.ibatis.annotations.Param;
import java.util.List;
@Mapper
public interface DiscussPostMapper {
//查询用户个人的所有帖子：用户ID、分页的起始行号、每页展示的数目
List<DiscussPost> selectDiscussPosts(int userId, int offset, int limit);
//查询行数：@Param 给参数起别名
//当SQL语句中需要动态的拼接条件，且方法内只有一个参数时，该参数必须起别名
int selectDiscussPostRows(@Param("userId") int userId);
}②UserMapper
package com.nowcoder.mycommunity.dao;
import com.nowcoder.mycommunity.entity.User;
import org.apache.ibatis.annotations.Mapper;
@Mapper
public interface UserMapper {
User selectById(int id);
User selectByName(String username);
User selectByEmail(String email);
int insertUser(User user);
int updateStatus(int id, int status);
int updateHeader(int id, String headerUrl);
int updatePassword(int id, String password);
}
6. 创建Mapper对应的xml文件
刚才创建了两个Mapper接口，里面只有方法，方法中的具体内容（即SQL语句）是放在Mapper对应的xml文件里的。
右键resources - new Directory - 起名：mapper
① discusspost-mapper.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.nowcoder.mycommunity.dao.DiscussPostMapper">
<!--定义了一个全局的查询字段-->
<sql id="selectFields">
id, user_id, title, content, type, status, create_time, comment_count, score
</sql>
<select id="selectDiscussPosts" resultType="DiscussPost">
<!--利用了上面的全局查询字段-->
select
<include refid="selectFields"></include>
from discuss_post
where status != 2
<!--条件拼接：如果没有参数userId，就不拼接if标签里的内容-->
<if test="userId != 0">
and user_id = #{userId}
</if>
<!--根据帖子类型，倒序排序。即置顶帖排到前面-->
<!--帖子类型相同时，新帖子排前面-->
order by type desc, create_time desc
<!--分页-->
limit #{offset}, #{limit}
</select>
<select id="selectDiscussPostRows" resultType="int">
select count(id)
from discuss_post
where status != 2
<if test="userId != 0">
and user_id = #{userId}
</if>
</select>
</mapper>②user-mapper.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.nowcoder.mycommunity.dao.UserMapper">
<sql id="selectFields">
id, username, password, salt, email, type, status, activation_code, header_url, create_time
</sql>
<!--相较于上一个，没有id，因为插入时id为主键，会自动增加-->
<sql id="insertFields">
username, password, salt, email, type, status, activation_code, header_url, create_time
</sql>
<select id="selectById" resultType="User">
select <include refid="selectFields"></include>
from user
where id = #{id}
</select>
<select id="selectByName" resultType="User">
select <include refid="selectFields"></include>
from user
where username = #{username}
</select>
<select id="selectByEmail" resultType="User">
select <include refid="selectFields"></include>
from user
where email = #{email}
</select>
<insert id="insertUser" parameterType="User" keyProperty="id">
insert into user (<include refid="insertFields"></include>)
value (#{username}, #{password},#{salt},#{email},#{type},#{status},#{activationCode},#{headerUrl},#{createTime})
</insert>
<update id="updateStatus">
update user set status = #{status} where id= #{id}
</update>
<update id="updateHeader">
update user set header_url = #{headerUrl} where id= #{id}
</update>
<update id="updatePassword">
update user set password = #{password} where id= #{id}
</update>
</mapper>7. Service
右键com.nowcoder.mycommunity，创建两个Service类，起名：service.XxxService。
① DiscussPostService
package com.nowcoder.mycommunity.service;
import com.nowcoder.mycommunity.dao.DiscussPostMapper;
import com.nowcoder.mycommunity.entity.DiscussPost;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
@Service
public class DiscussPostService {
@Autowired
private DiscussPostMapper discussPostMapper;
public List<DiscussPost> findDiscussPosts(int userId, int offset, int limit){
return discussPostMapper.selectDiscussPosts(userId, offset, limit);
}
public int findDiscussPostRows(int userId){
return discussPostMapper.selectDiscussPostRows(userId);
}
}
② UserService
package com.nowcoder.mycommunity.service;
import com.nowcoder.mycommunity.dao.UserMapper;
import com.nowcoder.mycommunity.entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class UserService {
@Autowired
private UserMapper userMapper;
public User findUserById(int id){
return userMapper.selectById(id);
}
}8. 控制器Controller
用来处理请求。
右键com.nowcoder.mycommunity，创建一个控制器类，起名：HomeController。
@Controller
public class HomeController {
@Autowired
private DiscussPostService discussPostService;
@Autowired
private UserService userService;
@RequestMapping(path = "/index", method = RequestMethod.GET)
public String getIndexPage(Model model, Page page){
//在方法调用前,SpringMVC会自动实例化Model和Page,并将Page注入Model
//因此在thymeleaf中可以直接访问page对象中的数据
//展示的总行数
//传入的id设为0时,我们不以id进行查询,相当于查所有
page.setRows(discussPostService.findDiscussPostRows(0));
page.setPath("/index");
List<DiscussPost> list = discussPostService.findDiscussPosts(0,page.getoffset(),page.getLimit());
List<Map<String, Object>> discussPosts = new ArrayList<>();
System.out.println("进入控制器");
if(list != null){
for(DiscussPost post:list){
Map<String, Object> map = new HashMap<>();
map.put("post",post);
User user = userService.findUserById(post.getUserId());
System.out.println(user);
map.put("user",user);
discussPosts.add(map);
}
}
model.addAttribute("discussPosts",discussPosts);
return "index";
}
@RequestMapping(path = "/aaa", method = RequestMethod.GET)
public String aaa(){
return "aaa";
}
}9. 首页 html
右键resources - new Directory - 起名为：templates，右键创建：index.html
<!doctype html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<link rel="icon" href="https://static.nowcoder.com/images/logo_87_87.png"/>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css" crossorigin="anonymous">
<link rel="stylesheet" th:href="@{/css/global.css}" />
<title>牛客网-首页</title>
</head>
<body>
<div class="nk-container">
<!-- 头部 -->
<header class="bg-dark sticky-top">
<div class="container">
<!-- 导航 -->
<nav class="navbar navbar-expand-lg navbar-dark">
<!-- logo -->
<a class="navbar-brand" href="#"></a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<!-- 功能 -->
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav mr-auto">
<li class="nav-item ml-3 btn-group-vertical">
<a class="nav-link" href="index.html">首页</a>
</li>
<li aclass="nav-item ml-3 btn-group-vertical">
<a class="nav-link position-relative" href="site/letter.html">消息<span class="badge badge-danger">12</span></a>
</li>
<li class="nav-item ml-3 btn-group-vertical">
<a class="nav-link" href="site/register.html">注册</a>
</li>
<li class="nav-item ml-3 btn-group-vertical">
<a class="nav-link" href="site/login.html">登录</a>
</li>
<li class="nav-item ml-3 btn-group-vertical dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
<img src="http://images.nowcoder.com/head/1t.png" class="rounded-circle" style="width:30px;"/>
</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item text-center" href="site/profile.html">个人主页</a>
<a class="dropdown-item text-center" href="site/setting.html">账号设置</a>
<a class="dropdown-item text-center" href="site/login.html">退出登录</a>
<div class="dropdown-divider"></div>
<span class="dropdown-item text-center text-secondary">nowcoder</span>
</div>
</li>
</ul>
<!-- 搜索 -->
<form class="form-inline my-2 my-lg-0" action="site/search.html">
<input class="form-control mr-sm-2" type="search" aria-label="Search" />
<button class="btn btn-outline-light my-2 my-sm-0" type="submit">搜索</button>
</form>
</div>
</nav>
</div>
</header>
<!-- 内容 -->
<div class="main">
<div class="container">
<div class="position-relative">
<!-- 筛选条件 -->
<ul class="nav nav-tabs mb-3">
<li class="nav-item">
<a class="nav-link active" href="#">最新</a>
</li>
<li class="nav-item">
<a class="nav-link" href="#">最热</a>
</li>
</ul>
<button type="button" class="btn btn-primary btn-sm position-absolute rt-0" data-toggle="modal" data-target="#publishModal">我要发布</button>
</div>
<!-- 弹出框 -->
<div class="modal fade" id="publishModal" tabindex="-1" role="dialog" aria-labelledby="publishModalLabel" aria-hidden="true">
<div class="modal-dialog modal-lg" role="document">
<div class="modal-content">
<div class="modal-header">
<h5 class="modal-title" id="publishModalLabel">新帖发布</h5>
<button type="button" class="close" data-dismiss="modal" aria-label="Close">
<span aria-hidden="true">×</span>
</button>
</div>
<div class="modal-body">
<form>
<div class="form-group">
<label for="recipient-name" class="col-form-label">标题：</label>
<input type="text" class="form-control" id="recipient-name">
</div>
<div class="form-group">
<label for="message-text" class="col-form-label">正文：</label>
<textarea class="form-control" id="message-text" rows="15"></textarea>
</div>
</form>
</div>
<div class="modal-footer">
<button type="button" class="btn btn-secondary" data-dismiss="modal">取消</button>
<button type="button" class="btn btn-primary" id="publishBtn">发布</button>
</div>
</div>
</div>
</div>
<!-- 提示框 -->
<div class="modal fade" id="hintModal" tabindex="-1" role="dialog" aria-labelledby="hintModalLabel" aria-hidden="true">
<div class="modal-dialog modal-lg" role="document">
<div class="modal-content">
<div class="modal-header">
<h5 class="modal-title" id="hintModalLabel">提示</h5>
</div>
<div class="modal-body" id="hintBody">
发布完毕!
</div>
</div>
</div>
</div>
<!-- 帖子列表 -->
<ul class="list-unstyled">
<li class="media pb-3 pt-3 mb-3 border-bottom" th:each="map:${discussPosts}">
<a href="site/profile.html">
<img th:src="${map.user.headerUrl}" class="mr-4 rounded-circle" alt="用户头像" style="width:50px;height:50px;">
</a>
<div class="media-body">
<h6 class="mt-0 mb-3">
<a href="#" th:utext="${map.post.title}">备战春招，面试刷题跟他复习，一个月全搞定！</a>
<span class="badge badge-secondary bg-primary" th:if="${map.post.type==1}">置顶</span>
<span class="badge badge-secondary bg-danger" th:if="${map.post.status==1}">精华</span>
</h6>
<div class="text-muted font-size-12">
<u class="mr-3" th:utext="${map.user.username}">寒江雪</u> 发布于 <b th:text="${#dates.format(map.post.createTime,'yyyy-MM-dd HH:mm:ss')}">2019-04-15 15:32:18</b>
<ul class="d-inline float-right">
<li class="d-inline ml-2">赞 11</li>
<li class="d-inline ml-2">|</li>
<li class="d-inline ml-2">回帖 7</li>
</ul>
</div>
</div>
</li>
</ul>
<!-- 分页 -->
<!--有数据时,才显示分页-->
<nav class="mt-5" th:if="${page.rows>0}">
<ul class="pagination justify-content-center">
<!--首页-->
<li class="page-item">
<!-- 下面会拼为 /index?current=1&limit=5 -->
<a class="page-link" th:href="@{${page.path}(current=1,limit=5)}">首页</a>
</li>
<!--上一页-->
<!-- | |中表示有静态变量,动态变量 -->
<!-- 当前页为第一页时,无法点击上一页 -->
<li th:class="|page-item ${page.current==1?'disabled':''}|">
<a class="page-link" th:href="@{${page.path}(current=${page.current-1})}">上一页</a>
</li>
<!--中间页码数-->
<!-- 为当前页时,点亮该页的图标 -->
<li th:class="|page-item ${i==page.current?'active':''}|" th:each="i:${#numbers.sequence(page.from,page.to)}">
<a class="page-link" th:href="@{${page.path}(current=${i})}" th:text="${i}">1</a>
</li>
<!--下一页-->
<li th:class="|page-item ${page.current==page.total?'disabled':''}|">
<a class="page-link" th:href="@{${page.path}(current=${page.current+1})}">下一页</a>
</li>
<!--末页-->
<!-- 当前页为第一页时,无法点击下一页 -->
<li class="page-item">
<a class="page-link" th:href="@{${page.path}(current=${page.total})}">末页</a>
</li>
</ul>
</nav>
</div>
</div>
<!-- 尾部 -->
<footer class="bg-dark">
<div class="container">
<div class="row">
<!-- 二维码 -->
<div class="col-4 qrcode">
<img src="https://uploadfiles.nowcoder.com/app/app_download.png" class="img-thumbnail" style="width:136px;" />
</div>
<!-- 公司信息 -->
<div class="col-8 detail-info">
<div class="row">
<div class="col">
<ul class="nav">
<li class="nav-item">
<a class="nav-link text-light" href="#">关于我们</a>
</li>
<li class="nav-item">
<a class="nav-link text-light" href="#">加入我们</a>
</li>
<li class="nav-item">
<a class="nav-link text-light" href="#">意见反馈</a>
</li>
<li class="nav-item">
<a class="nav-link text-light" href="#">企业服务</a>
</li>
<li class="nav-item">
<a class="nav-link text-light" href="#">联系我们</a>
</li>
<li class="nav-item">
<a class="nav-link text-light" href="#">免责声明</a>
</li>
<li class="nav-item">
<a class="nav-link text-light" href="#">友情链接</a>
</li>
</ul>
</div>
</div>
<div class="row">
<div class="col">
<ul class="nav btn-group-vertical company-info">
<li class="nav-item text-white-50">
公司地址：北京市朝阳区大屯路东金泉时代3-2708北京牛客科技有限公司
</li>
<li class="nav-item text-white-50">
联系方式：010-60728802(电话) admin@nowcoder.com
</li>
<li class="nav-item text-white-50">
牛客科技?2018 All rights reserved
</li>
<li class="nav-item text-white-50">
京ICP备14055008号-4
<img src="http://static.nowcoder.com/company/images/res/ghs.png" style="width:18px;" />
京公网安备 11010502036488号
</li>
</ul>
</div>
</div>
</div>
</div>
</div>
</footer>
</div>
<script src="https://code.jquery.com/jquery-3.3.1.min.js" crossorigin="anonymous"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" crossorigin="anonymous"></script>
<script th:src="@{/js/global.js}"></script>
<script th:src="@{js/index.js}"></script>
</body>
</html>
10. 难点说明
①首先Page类与控制器方法的一些交互
Page类有4个属性：当前页、显示页数的上限、总页数、查询路径。
