本文是基于springboot框架下的查询。
一：基本配置：
1.仓库依赖
<repositories>
<repository>
<id>alimaven</id>
<name>aliyun maven</name>
<url>http://maven.aliyun.com/nexus/content/groups/public/</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
</repositories>
<pluginRepositories>
<pluginRepository>
<id>alimaven</id>
<name>aliyun maven</name>
<url>http://maven.aliyun.com/nexus/content/groups/public/</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
</pluginRepository>
</pluginRepositories>
2.springboot框架依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!--添加thymeleaf依赖-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<!--mybatis持久层org映射框架-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.3.1.tmp</version>
</dependency>
3.数据库依赖
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
二. 三种查询方式
1.like对象查询 (Dept为数据库表,return index为返回的前端页面)
public String index(
String name,
Model model) {
QueryWrapper<Dept> queryWrapper= new QueryWrapper<>();
if (name!=null && name.trim().length()>0){
queryWrapper.like("name", name.trim());
}
List<Dept> list = deptService.list(queryWrapper);
model.addAttribute("list",list);
model.addAttribute("name",name);
return "index";
}
1.1 Dao层注解控制台输出sql语句
@Select("select * from dept where name like #{name}")；
2.mybatis注解查询
public String index(
String name,
Model model) {
List<Dept> depts=null;
if (name!=null && name.trim().length()>0){
depts = deptService.list2like("%" + name + "%");
}else{
depts=deptService.list();
}
model.addAttribute("list", depts);
model.addAttribute("name", name);
return "index";
}
3.mybatis xml查询
3.1 配置扫描xml文件
mybatis-plus: mapper-locations: classpath:/mapper/*.xml
3.2定义mapper模板
<?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="包对应的Dao类">
<!--
list2likeXml 方法名
resultType 返回结果的类型
-->
<select id="对应Dao类的方法名l" resultType="com.kede.springbootdemo4dept.entity.Dept">
select * from dept
<where>
<if test="name !=null and name != ''">
and name like concat('%',#{name},'%')
</if>
</where>
</select>
</mapper>
3.3controller层代码
public String index(
String name,
Model model) {
List<Dept> depts= deptService.list2likeXml(name);
model.addAttribute("list", depts);
model.addAttribute("name", name);
return "index";
}
4.Dao层的方法
public interface DeptDao extends BaseMapper<Dept> {
//org.apache.ibatis.annotations.Param 类似于springmvc里面的@RequestParam
//#{name} 和@Param("name") 对应
@Select("select * from dept where name like #{name}")//sql语句，从部门表搜素相关
List<Dept> list2like(@Param("name") String name);
List<Dept> list2likeXml(String name);
}
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