标签：set NAME int 笔记 news TABLE 第三课 id
目录
三、ViewObject：方便传递任何数据到Velocity
一、数据库创建、CRUD
推荐使用GUI转SQL的方式生成SQL脚本。
| 常用数据类型 |
| int |
| varchar(n) |
| datetime |
| float(m,d) |
| text，65535 |
INSERT INTO table_name (列1, 列2,...) VALUES (值1, 值2,....)
SELECT */列名称 FROM 表名称
UPDATE 表名称 SET 列名称 = 新值 WHERE 列名称 = 某值
DELETE FROM 表名称 WHERE 列名称 = 值
SELECT {COLA,COLB,*} FROM {TABLE} WHERE {CONDITION}
ORDER BY {COL} DESC
LIMIT {OFF},{COUNT}
二、MyBatis集成
spring.datasource.url=jdbc:mysql://localhost:3306/toutiao?useUnicode=true&characterEncoding=utf8&useSSL=false
spring.datasource.username=root
spring.datasource.password=nowcoder
#添加mybatis配置文件
mybatis.config-location=classpath:mybatis-config.xml
#logging.level.root=DEBUG
spring.velocity.suffix=.html
spring.velocity.cache=false
spring.velocity.toolbox-config-location=toolbox.xml注解配置：
@Mapper
public interface UserDAO {
String TABLE_NAME = "user";
String INSET_FIELDS = " name, password, salt, head_url ";
String SELECT_FIELDS = " id, name, password, salt, head_url";
@Insert({"insert into ", TABLE_NAME, "(", INSET_FIELDS,
") values (#{name},#{password},#{salt},#{headUrl})"})
int addUser(User user);
@Select({"select ", SELECT_FIELDS, " from ", TABLE_NAME, " where id=#{id}"})
User selectById(int id);
@Select({"select ", SELECT_FIELDS, " from ", TABLE_NAME, " where name=#{name}"})
User selectByName(String name);
@Update({"update ", TABLE_NAME, " set password=#{password} where id=#{id}"})
void updatePassword(User user);
//一般是通过update ... set statue = 0 where ...来进行删除
@Delete({"delete from ", TABLE_NAME, " where id=#{id}"})
void deleteById(int id);
}XML配置：在相同的包目录下定义的同名XML
文件名：NewDAO.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.dao.NewsDAO">
<sql id="table">news</sql>
<sql id="selectFields">id,title, link, image, like_count, comment_count,created_date,user_id
</sql>
<select id="selectByUserIdAndOffset" resultType="com.nowcoder.model.News">
SELECT
<include refid="selectFields"/>
FROM
<include refid="table"/>
<if test="userId != 0">
WHERE user_id = #{userId}
</if>
ORDER BY id DESC
LIMIT #{offset},#{limit}
</select>
</mapper>NewDAO.java
@Mapper
public interface NewsDAO {
String TABLE_NAME = "news";
String INSERT_FIELDS = " title, link, image, like_count, comment_count, created_date, user_id ";
String SELECT_FIELDS = " id, " + INSERT_FIELDS;
@Insert({"insert into ", TABLE_NAME, "(", INSERT_FIELDS,
") values (#{title},#{link},#{image},#{likeCount},#{commentCount},#{createdDate},#{userId})"})
int addNews(News news);
@Select({"select ", SELECT_FIELDS , " from ", TABLE_NAME, " where id=#{id}"})
News getById(int id);
@Update({"update ", TABLE_NAME, " set comment_count = #{commentCount} where id=#{id}"})
int updateCommentCount(@Param("id") int id, @Param("commentCount") int commentCount);
@Update({"update ", TABLE_NAME, " set like_count = #{likeCount} where id=#{id}"})
int updateLikeCount(@Param("id") int id, @Param("likeCount") int likeCount);
//这里用到了@Param的注解，因为NewDAO.xml中会使用到
List<News> selectByUserIdAndOffset(@Param("userId") int userId, @Param("offset") int offset,
@Param("limit") int limit);
}
三、ViewObject：方便传递任何数据到Velocity
ViewObject定义在Model包下：
public class ViewObject {
private Map<String, Object> objs = new HashMap<String, Object>();
public void set(String key, Object value) {
objs.put(key, value);
}
public Object get(String key) {
return objs.get(key);
}
}
例如，获取News的方法：
private List<ViewObject> getNews(int userId, int offset, int limit) {
List<News> newsList = newsService.getLatestNews(userId, offset, limit);
int localUserId = hostHolder.getUser() != null ? hostHolder.getUser().getId() : 0;
List<ViewObject> vos = new ArrayList<>();
for (News news : newsList) {
ViewObject vo = new ViewObject();
vo.set("news", news);
vo.set("user", userService.getUser(news.getUserId()));
if (localUserId != 0) {
vo.set("like", likeService.getLikeStatus(localUserId, EntityType.ENTITY_NEWS, news.getId()));
} else {
vo.set("like", 0);
}
vos.add(vo);
}
return vos;
}
@RequestMapping(path = {"/", "/index"}, method = {RequestMethod.GET, RequestMethod.POST})
public String index(Model model,
@RequestParam(value = "pop", defaultValue = "0") int pop) {
model.addAttribute("vos", getNews(0, 0, 10));
if (hostHolder.getUser() != null) {
pop = 0;
}
model.addAttribute("pop", pop);
return "home";
}做成一个List，然后就可以在Velocity中写for语句把News展示出来了！
#foreach ($vo in $vos)
......
四、DataTool：Velocity自带工具类导入
实现功能：将News按照时间分开
编写toolbox.xml，里面定义DataTool，作用范围是整个spring
<toolbox>
<tool>
<key>date</key>
<scope>application</scope>
<class>org.apache.velocity.tools.generic.DateTool</class>
</tool>
</toolbox>然后在application.properties中添加：
spring.velocity.toolbox-config-location=toolbox.xmlhome.html中：
#set($cur_date = '')
#foreach($vo in $vos)
#if ($cur_date != $date.format('yyyy-MM-dd', $vo.news.createdDate))
#if ($foreach.index > 0)
</div> ## 上一个要收尾
#end
#set($cur_date = $date.format('yyyy-MM-dd', $vo.news.createdDate))
<h3 class="date">
<i class="fa icon-calendar"></i>
<span>头条资讯 $date.format('yyyy-MM-dd', $vo.news.createdDate)</span>
</h3>
<div class="posts">
#end
.......
##后面还有标签：set,NAME,int,笔记,news,TABLE,第三课,id 来源： https://blog.csdn.net/qq_35514456/article/details/118901163
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