[Java知识库]一 开发社区首页

分布实现
开发社区首页，显示前10个帖子
开发分页组件，分页和显示所有帖子
开发步骤：
1 创建帖子实体类

package com.now.jiancommunity.entity;

import java.util.Date;

public class DiscussPost {
    private int userId;
    private String title;
    private String content;
    private int discussType;
    private int status;
    private Date CreateTime;
    private int commnetCount;
    private int score;

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    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 int getDiscussType() {
        return discussType;
    }

    public void setDiscussType(int discussType) {
        this.discussType = discussType;
    }

    public int getStatus() {
        return status;
    }

    public void setStatus(int status) {
        this.status = status;
    }

    public Date getCreateTime() {
        return CreateTime;
    }

    public void setCreateTime(Date createTime) {
        CreateTime = createTime;
    }

    public int getCommnetCount() {
        return commnetCount;
    }

    public void setCommnetCount(int commnetCount) {
        this.commnetCount = commnetCount;
    }

    public int getScore() {
        return score;
    }

    public void setScore(int score) {
        this.score = score;
    }

    @Override
    public String toString() {
        return "DiscussPost{" +
                "userId=" + userId +
                ", title='" + title + '\'' +
                ", content='" + content + '\'' +
                ", discussType=" + discussType +
                ", status=" + status +
                ", CreateTime=" + CreateTime +
                ", commnetCount=" + commnetCount +
                ", score=" + score +
                '}';
    }
}

根据请求执行过程分布开发
2 建立DiscussPostMapper接口

@Mapper
public interface DiscussPostMapper {
    List<DiscussPost> selectDiscussPosts(int userId,int offset,int limit);

    int selectDiscussRows(@Param("userId") int userId);


}

XML实现接口

<?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.now.jiancommunity.dao.DiscussPostMapper">

    <sql id="selectFields">
        id, user_id, title, content, type, status, create_time, comment_count, score
    </sql>
    <select id="selectDiscussPosts" resultType="DiscussPost">
        select <include refid="selectFields"></include>
        from discuss_post
        where status != 2
        <if test="userId != 0">
            and user_id=#{userId}
        </if>
        order by type desc ,create_time desc
        limit #{offset} ,#{limit}
    </select>
    <select id="selectDiscussRows" resultType="int">
        select count(id)
        from discuss_post
        where status != 2
        <if test="userId != 0">
            and user_id=#{userId}
        </if>

    </select>

</mapper>

3 服务层建立DiscussPostService

@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.selectDiscussRows(userId);
    }
}

4 控制层建立HomeController

@Controller
public class HomeController {
    @Autowired
    private DiscussPostService discussPostService;

    @Autowired
    private UserService userService;

    @RequestMapping(path= "/index" ,method = RequestMethod.GET)
    public String getIndex(Model model, Page page){
        page.setPath("/index");
        page.setRows(discussPostService.findDiscussPostRows(0));

        List<DiscussPost> discussPostList = discussPostService.findDiscussPosts(0, page.getOffset(), page.getLimit());
        ArrayList<Map<String,Object>> discussPosts=new ArrayList<>();
        if(discussPostList != null) {
            for(DiscussPost post:discussPostList){
                Map<String ,Object> map=new HashMap<>();
                map.put("post",post);
                User user = userService.findUserById(post.getUserId());
                map.put("user",user);
                discussPosts.add(map);
            }

        }
        model.addAttribute("discussPosts",discussPosts);
        return "/index";
    }

}

5 修改index.html界面
遍历discussPosts结合，得到post帖子map

th:each="map:${discussPosts}"

修改帖子列表
头像

th:src="${map.user.headerUrl}"

帖子主题

th:utext="${map.post.title}"

帖子状态

 th:if="${map.post.status==1}"

帖子类型

th:if="${map.post.discussType==1}"

帖子姓名

th:utext="${map.user.username}"

创建时间

th:text="${#dates.format(map.post.createTime,'yyyy-MM-dd HH:mm:ss')}"

分页

<nav class="mt-5" th:if="${page.rows>0}" th:fragment="pagination">
				<ul class="pagination justify-content-center">
					<li class="page-item">
						<a class="page-link" th:href="@{${page.path}(current=1)}">首页</a>
					</li>
					<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>
					<li th:class="|page-item ${i==page.current?'active':''}|" th:each="i:${#numbers.sequence(page.from,page.to)}">
						<a class="page-link" href="#" th:text="${i}">1</a>
					</li>
					<li th:class="|page-item ${page.current==page.total?'disabled':''}|">
						<a class="page-link" th:href="@{${page.path}(current=${page.current+1})}">下一页</a>
					</li>
					<li class="page-item">
						<a class="page-link" th:href="@{${page.path}(current=${page.total})}">末页</a>
					</li>
				</ul>
			</nav>