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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