412 lines
9.7 KiB
Markdown
412 lines
9.7 KiB
Markdown
# 开发社区首页
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---
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## DiscussPost 讨论帖
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### Entity
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### DAO
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- Mapper 接口 `DiscussPostMapper`
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- 对应的 xml 配置文件 `discusspost-mapper.xml`
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`@Param` 注解用于给参数起别名，**如果只有一个参数**，并且需要在 `<if>` 里使用，则必须加别名
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```java
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@Mapper
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public interface DiscussPostMapper {
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/**
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* 分页查询讨论贴信息
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*
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* @param userId 当传入的 userId = 0 时查找所有用户的帖子
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* 当传入的 userId != 0 时，查找该指定用户的帖子
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* @param offset 每页的起始索引
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* @param limit 每页显示多少条数据
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* @return
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*/
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List<DiscussPost> selectDiscussPosts(int userId, int offset, int limit);
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/**
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* 查询讨论贴的个数
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* @param userId 当传入的 userId = 0 时计算所有用户的帖子总数
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* 当传入的 userId ！= 0 时计算该指定用户的帖子总数
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* @return
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*/
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int selectDiscussPostRows(@Param("userId") int userId);
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}
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```
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对应的 Mapper：
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE mapper
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PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
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"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
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<mapper namespace="com.greate.community.dao.DiscussPostMapper">
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<sql id = "selectFields">
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id, user_id, title, content, type, status, create_time, comment_count, score
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</sql>
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<!--分页查询讨论贴信息-->
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<!--不显示拉黑的帖子, 按照是否置顶和创建时间排序-->
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<select id = "selectDiscussPosts" resultType="DiscussPost">
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select <include refid="selectFields"></include>
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from discuss_post
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where status != 2
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<if test = "userId!=0">
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and user_id = #{userId}
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</if>
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order by type desc, create_time desc
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limit #{offset}, #{limit}
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</select>
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<!--查询讨论贴的个数-->
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<select id = "selectDiscussPostRows" resultType="int">
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select count(id)
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from discuss_post
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where status != 2
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<if test = "userId != 0">
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and user_id = #{userId}
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</if>
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</select>
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</mapper>
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```
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### Service
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关于自动注入 Mapper 报错问题：可参考 [关于IDEA中@Autowired 注解报错~图文](https://www.cnblogs.com/taopanfeng/p/10994075.html)
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```java
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@Service
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public class DiscussPostSerivce {
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@Autowired
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private DiscussPostMapper discussPostMapper;
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/**
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* 分页查询讨论帖信息
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*
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* @param userId 当传入的 userId = 0 时查找所有用户的帖子
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* 当传入的 userId != 0 时，查找该指定用户的帖子
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* @param offset 每页的起始索引
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* @param limit 每页显示多少条数据
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* @return
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*/
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public List<DiscussPost> findDiscussPosts (int userId, int offset, int limit) {
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return discussPostMapper.selectDiscussPosts(userId, offset, limit);
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}
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/**
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* 查询讨论贴的个数
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* @param userId 当传入的 userId = 0 时计算所有用户的帖子总数
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* 当传入的 userId ！= 0 时计算该指定用户的帖子总数
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* @return
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*/
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public int findDiscussPostRows (int userId) {
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return discussPostMapper.selectDiscussPostRows(userId);
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}
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}
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```
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## User
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### Entity
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### DAO
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```java
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@Mapper
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public interface UserMapper {
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/**
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* 根据 id 查询用户
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* @param id
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* @return
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*/
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User selectById (int id);
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/**
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* 根据 username 查询用户
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* @param username
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* @return
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*/
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User selectByName(String username);
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/**
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* 根据 email 查询用户
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* @param email
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* @return
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*/
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User selectByEmail(String email);
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/**
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* 插入用户（注册）
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* @param user
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* @return
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*/
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int insertUser(User user);
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/**
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* 修改用户状态
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* @param id
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* @param status 0：未激活，1：已激活
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* @return
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*/
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int updateStatus(int id, int status);
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/**
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* 修改头像
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* @param id
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* @param headerUrl
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* @return
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*/
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int updateHeader(int id, String headerUrl);
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/**
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* 修改密码
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* @param id
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* @param password
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* @return
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*/
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int updatePassword(int id, String password);
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}
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```
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对应的 mapper.xml：
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```xml
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE mapper
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PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
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"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
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<mapper namespace="com.greate.community.dao.UserMapper">
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<sql id = "insertFields">
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username, password, salt, email, type, status, activation_code, header_url, create_time
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</sql>
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<sql id = "selectFields">
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id, username, password, salt, email, type, status, activation_code, header_url, create_time
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</sql>
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<!--根据 Id 查询用户信息-->
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<select id = "selectById" resultType = "User">
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select <include refid="selectFields"></include>
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from user
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where id = #{id}
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</select>
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<!--根据 Username 查询用户信息-->
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<select id="selectByName" resultType="User">
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select <include refid="selectFields"></include>
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from user
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where username = #{username}
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</select>
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<!--根据 email 查询用户信息-->
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<select id="selectByEmail" resultType="User">
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select <include refid="selectFields"></include>
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from user
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where email = #{email}
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</select>
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<!--插入用户信息（注册）-->
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<insert id="insertUser" parameterType="User" keyProperty="id">
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insert into user (<include refid="insertFields"></include>)
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values(#{username}, #{password}, #{salt}, #{email}, #{type}, #{status}, #{activationCode}, #{headerUrl}, #{createTime})
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</insert>
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<!--修改用户状态-->
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<update id="updateStatus">
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update user set status = #{status} where id = #{id}
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</update>
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<!--修改用户头像-->
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<update id="updateHeader">
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update user set header_url = #{headerUrl} where id = #{id}
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</update>
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<!--修改密码-->
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<update id="updatePassword">
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update user set password = #{password} where id = #{id}
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</update>
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</mapper>
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```
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### Service
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```java
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@Service
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public class UserService {
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@Autowired
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private UserMapper userMapper;
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public User findUserById (int id) {
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return userMapper.selectById(id);
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}
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}
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```
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## Page 分页
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```java
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/**
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* 封装分页相关的信息
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*/
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public class Page {
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// 当前的页码
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private int current = 1;
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// 单页显示的帖子数量上限
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private int limit = 10;
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// 帖子总数（用于计算总页数）
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private int rows;
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// 查询路径（用于复用分页链接, 因为我们不只在首页中有分页，其他界面也会有分页）
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private String path;
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public int getCurrent() {
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return current;
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}
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public void setCurrent(int current) {
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if (current >= 1) {
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this.current = current;
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}
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}
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public int getLimit() {
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return limit;
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}
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public void setLimit(int limit) {
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if (current >= 1 && limit <= 100) {
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this.limit = limit;
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}
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}
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public int getRows() {
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return rows;
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}
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public void setRows(int rows) {
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if (rows >= 0) {
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this.rows = rows;
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}
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}
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public String getPath() {
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return path;
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}
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public void setPath(String path) {
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this.path = path;
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}
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/**
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* 获取当前页的起始索引 offset
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* @return
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*/
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public int getOffset() {
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return current * limit - limit;
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}
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/**
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* 获取总页数
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* @return
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*/
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public int getTotal() {
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if (rows % limit == 0) {
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return rows / limit;
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}
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else {
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return rows / limit + 1;
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}
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}
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/**
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* 获取分页栏起始页码
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* 分页栏显示当前页码及其前后两页
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* @return
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*/
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public int getFrom() {
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int from = current - 2;
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return from < 1 ? 1 : from;
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}
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/**
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* 获取分页栏结束页码
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* @return
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*/
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public int getTo() {
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int to = current + 2;
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int total = getTotal();
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return to > total ? total : to;
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}
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}
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```
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## Controller
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```java
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@Controller
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public class HomeController {
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@Autowired
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private DiscussPostSerivce discussPostSerivce;
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@Autowired
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private UserService userService;
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@GetMapping("/index")
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public String getIndexPage(Model model, Page page) {
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// 获取总页数
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page.setRows(discussPostSerivce.findDiscussPostRows(0));
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page.setPath("/index");
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// 分页查询
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List<DiscussPost> list = discussPostSerivce.findDiscussPosts(0, page.getOffset(), page.getLimit());
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// 封装帖子和该帖子对应的用户信息
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List<Map<String, Object>> discussPosts = new ArrayList<>();
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if (list != null) {
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for (DiscussPost post : list) {
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Map<String, Object> map = new HashMap<>();
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map.put("post", post);
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User user = userService.findUserById(post.getUserId());
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map.put("user", user);
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discussPosts.add(map);
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}
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}
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model.addAttribute("discussPosts", discussPosts);
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return "index";
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}
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}
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```
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🚩 小 Tip：这里不用把 Page 放入 model（`model.addAttribute("page", page);`
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因为在方法调用之前，Spring MVC 会自动实例化 Model 和 Page，并将 Page 注入 Model，所以，在 Thymeleaf 中可以直接访问 Page 对象中的数据
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## 前端界面 index.html
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```html
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th:each="map:${discussPosts}"
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```
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表示将每次遍历 `discussPosts` 取出的变量称为 `map`
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