Spring Boot 项目之社区首页开发

开发顺序：数据访问层（1.实体类（entity）->2.Dao层的mapper->3.mapper.xml->4.test）->业务层（service）->控制层（controller）

实体类entity：DisscussPost

把表discusspost中的字段进行罗列。

package com.nowcoder.community.entity;

import java.util.Date;

public class DisscussPost {

    private int id;
    private int userId;
    private String title;
    private String content;
    private int type; // 0:普通 1：置顶
    private int status;
    private Date createTime;
    private int commentCount;
    private int score;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    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 getType() {
        return type;
    }

    public void setType(int type) {
        this.type = type;
    }

    public int getStatus() {
        return status;
    }

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

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public int getCommentCount() {
        return commentCount;
    }

    public void setCommentCount(int commentCount) {
        this.commentCount = commentCount;
    }

    public int getScore() {
        return score;
    }

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

    @Override
    public String toString() {
        return "DisscussPost{" +
                "id=" + id +
                ", userId=" + userId +
                ", title='" + title + ''' +
                ", content='" + content + ''' +
                ", type=" + type +
                ", status=" + status +
                ", createTime=" + createTime +
                ", commentCount=" + commentCount +
                ", score=" + score +
                '}';
    }
}

Dao层写一个mapper接口：DiscussPostMapper

package com.nowcoder.community.dao;

import com.nowcoder.community.entity.DisscussPost;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;

import java.util.List;

@Mapper // 加上注解才能被容器自动扫描该接口，自动实现和装配
public interface DiscussPostMapper {

    /**
     * 首页查询功能的两个方法：selectDiscussPosts()、selectDiscussPostRows()
     *
     * 1.搜索帖子：结果是一个集合,集合里装的是帖子对象。
     * 2.userId用于后面个人主页的开发，可以动态输入，传入时可以在个人主页中查看个人帖子，当然默认也可以不传入。SQL语句因此也是动态的
     * 3.分页：offset表示每一页起始行的行号，limit表示每一页最多显示的数据。
     * @param userId
     * @return
     */
    List<DisscussPost> selectDiscussPosts(int userId, int offset, int limit);

    // @Param注解用于给参数取别名，
    // 且这个方法有且只有一个参数，并且在<if>里使用，参数之前必须取别名
    int selectDiscussPostRows(@Param("userId") int userId);

}

编写mapper实现方法的语句：discusspost-mapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.nowcoder.community.dao.DiscussPostMapper">

    <sql id="selectFields">
        id, user_id, title, content, type, status, create_time, comment_count, score
    </sql>

<!--    获取帖子，状态不为2，类型倒序排，也即精华置顶，创建时间倒序排：也即新创建的帖子置顶    -->
    <select id="selectDiscussPosts" resultType="DisscussPost">
        select <include refid="selectFields"></include>
        from discuss_post
        where status != 2
<!--        使用if标签的test属性对userId进行判断，动态输入sql语句-->
        <if test="userId!=0">
            and user_id = #{userId}
        </if>
        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
        <!--        使用if标签的test属性对userId进行判断，动态输入sql语句-->
        <if test="userId!=0">
            and user_id = #{userId}
        </if>
    </select>
</mapper>

Test

package com.nowcoder.community;

import com.nowcoder.community.dao.DiscussPostMapper;
import com.nowcoder.community.dao.UserMapper;
import com.nowcoder.community.entity.DisscussPost;
import com.nowcoder.community.entity.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringRunner;

import java.util.Date;
import java.util.List;

@RunWith(SpringRunner.class)
@SpringBootTest
@ContextConfiguration(classes = CommunityApplication.class)
public class MapperTest {

    @Autowired
    private DiscussPostMapper discussPostMapper;

    @Test
    public void testSelectPosts() {
        List<DisscussPost> disscussPostList = discussPostMapper.selectDiscussPosts(149, 0, 10);
        for(DisscussPost post : disscussPostList) {
            System.out.println(post);
        }

        int rows = discussPostMapper.selectDiscussPostRows(149);
        System.out.println(rows);
    }
}

service层

类：DiscussPostService

package com.nowcoder.community.service;

import com.nowcoder.community.dao.DiscussPostMapper;
import com.nowcoder.community.entity.DisscussPost;
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<DisscussPost> findDiscussPosts(int userId, int offset, int limit) {
        return discussPostMapper.selectDiscussPosts(userId, offset, limit);
    }

    public int findDiscussPostRows(int userId) {
        return discussPostMapper.selectDiscussPostRows(userId);
    }
}

类：UserService

package com.nowcoder.community.service;

import com.nowcoder.community.dao.UserMapper;
import com.nowcoder.community.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);
    }
}

controller层

添加静态资源和首页前端字段

HomeController:

package com.nowcoder.community.controller;

import com.nowcoder.community.entity.DisscussPost;
import com.nowcoder.community.entity.User;
import com.nowcoder.community.service.DiscussPostService;
import com.nowcoder.community.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@Controller
public class HomeController {

    @Autowired
    private DiscussPostService discussPostService;

    @Autowired
    private UserService userService;

    @RequestMapping(path = "/index", method = RequestMethod.GET)
    public String getIndexPage(Model model) {
        List<DisscussPost> list = discussPostService.findDiscussPosts(0, 0, 10);
        List<Map<String, Object>> discussPosts = new ArrayList<>();
        if (list != null) {
            for (DisscussPost post : list) {
                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";
    }
}