本文是基于springboot框架下的查詢。

一：基本配置：

1.倉(cāng)庫(kù)依賴

<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框架依賴

<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <!--添加thymeleaf依賴--> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-thymeleaf</artifactId> </dependency> <!--mybatis持久層org映射框架--> <dependency> <groupId>com.baomidou</groupId> <artifactId>mybatis-plus-boot-starter</artifactId> <version>3.3.1.tmp</version> </dependency>

3.數(shù)據(jù)庫(kù)依賴

<dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> </dependency>

二. 三種查詢方式

1.like對(duì)象查詢 (Dept為數(shù)據(jù)庫(kù)表,return index為返回的前端頁(yè)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層注解控制臺(tái)輸出sql語(yǔ)句

@Select('select * from dept where name like #{name}')；

2.mybatis注解查詢

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查詢

3.1 配置掃描xml文件

mybatis-plus: mapper-locations: classpath:/mapper/*.xml

3.2定義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='包對(duì)應(yīng)的Dao類'> <!-- list2likeXml 方法名 resultType 返回結(jié)果的類型 --> <select 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層代碼

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層的方法

public interface DeptDao extends BaseMapper<Dept> { //org.apache.ibatis.annotations.Param 類似于springmvc里面的@RequestParam //#{name} 和@Param('name') 對(duì)應(yīng) @Select('select * from dept where name like #{name}')//sql語(yǔ)句，從部門(mén)表搜素相關(guān) List<Dept> list2like(@Param('name') String name); List<Dept> list2likeXml(String name);}

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