Mybatis的强大条件构造器 QueryWrapper

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Mybatis的高效开发

QueryWrapper的使用代码
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package com.lqf.crud;import com.baomidou.mybatisplus.core.conditions.Wrapper;
import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.conditions.update.UpdateWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.core.toolkit.Constants;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.lqf.crud.bean.crm.User;
import com.lqf.crud.dao.crm.UserMapper;
import com.sun.org.apache.xerces.internal.util.EntityResolverWrapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.session.RowBounds;
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.junit4.SpringRunner;
import org.springframework.web.jsf.el.WebApplicationContextFacesELResolver;import javax.naming.Name;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;@RunWith(SpringRunner.class)
@SpringBootTest
public class QueryWrapperTests {@Autowiredprivate UserMapper mapper;/*** <p>* 根据根据 entity 条件，删除记录,QueryWrapper实体对象封装操作类（可以为 null）* 下方获取到queryWrapper后删除的查询条件为name字段为null的and年龄大于等于12的and email字段不为null的* 同理写法条件添加的方式就不做过多介绍了。* </p>*/@Testpublic void delete() {QueryWrapper<User> queryWrapper = new QueryWrapper<>();queryWrapper.isNull("name").ge("age", 12).isNotNull("email");int delete = mapper.delete(queryWrapper);System.out.println("delete return count = " + delete);}/*** <p>* 根据 entity 条件，查询一条记录,* 这里和上方删除构造条件一样，只是seletOne返回的是一条实体记录，当出现多条时会报错* </p>*/@Testpublic void selectOne() {QueryWrapper<User> queryWrapper = new QueryWrapper<>();queryWrapper.eq("name", "lqf");User user = mapper.selectOne(queryWrapper);System.out.println(user);}/*** <p>* 根据 Wrapper 条件，查询总记录数* </p>** @param queryWrapper 实体对象*/@Testpublic void selectCount() {QueryWrapper<User> queryWrapper = new QueryWrapper<>();queryWrapper.eq("name", "lqf");Integer count = mapper.selectCount(queryWrapper);System.out.println(count);}/*** <p>* 根据 entity 条件，查询全部记录* </p>** @param queryWrapper 实体对象封装操作类（可以为 null）为null查询全部*/@Testpublic void selectList() {List<User> list = mapper.selectList(null);System.out.println(list);}/*** <p>* 根据 Wrapper 条件，查询全部记录* </p>** @param queryWrapper 实体对象封装操作类（可以为 null）*/@Testpublic void selectMaps() {QueryWrapper<User> queryWrapper = new QueryWrapper<>();queryWrapper.isNotNull("name");List<Map<String, Object>> maps = mapper.selectMaps(queryWrapper);for (Map<String, Object> map : maps) {System.out.println(map);}}/*** 打印结果* {name=lqf, id=1046282328366391406, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391407, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391408, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391409, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391410, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391411, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391412, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391413, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391414, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391415, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391416, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391417, age=12, email=lqf@163.com, status=false}* {name=lqf, id=1046282328366391418, age=12, email=lqf@163.com, status=false}* json类型的键值对模式*//*** <p>* 根据 entity 条件，查询全部记录（并翻页）* </p>** @param page         分页查询条件（可以为 RowBounds.DEFAULT）* @param queryWrapper 实体对象封装操作类（可以为 null）*/@Testpublic void selectPage() {Page<User> page = new Page<>(1, 5);QueryWrapper<User> queryWrapper = new QueryWrapper<>();IPage<User> userIPage = mapper.selectPage(page, queryWrapper);System.out.println(userIPage);}/*** 打印结果* ==>  Preparing: SELECT COUNT(1) FROM user* ==> Parameters:* <==    Columns: COUNT(1)* <==        Row: 100* ==>  Preparing: SELECT id,name,age,email,status FROM user LIMIT 0,5* ==> Parameters:* <==    Columns: id, name, age, email, status* <==        Row: 1046282328366391319, lqf, 12, lqf@163.com, 0* <==        Row: 1046282328366391320, lqf, 12, lqf@163.com, 0* <==        Row: 1046282328366391321, lqf, 12, lqf@163.com, 0* <==        Row: 1046282328366391322, lqf, 12, lqf@163.com, 0* <==        Row: 1046282328366391323, lqf, 12, lqf@163.com, 0* <==      Total: 5*** 这里需要在项目中加入分页插件*   @Bean*     public PaginationInterceptor paginationInterceptor() {*         return new PaginationInterceptor();*     }*//*** <p>* 根据 Wrapper 条件，查询全部记录（并翻页）* </p>** @param page         分页查询条件* @param queryWrapper 实体对象封装操作类*/@Testpublic void selectMapsPage() {Page<User> page = new Page<>(1, 5);QueryWrapper<User> queryWrapper = new QueryWrapper<>();IPage<Map<String, Object>> mapIPage = mapper.selectMapsPage(page, queryWrapper);System.out.println(mapIPage);}/*** 和上个分页同理只是返回类型不同*//*** <p>* 根据 whereEntity 条件，更新记录* </p>** @param entity        实体对象 (set 条件值,不能为 null)* @param updateWrapper 实体对象封装操作类（可以为 null,里面的 entity 用于生成 where 语句）*/@Testpublic void update() {//修改值User user = new User();user.setStatus(true);user.setName("zhangsan");//修改条件sUpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();userUpdateWrapper.eq("name", "lqf");int update = mapper.update(user, userUpdateWrapper);System.out.println(update);}/*** 打印结果* ==>  Preparing: UPDATE user SET name=?, status=? WHERE name = ?* ==> Parameters: zhangsan(String), true(Boolean), lqf(String)* <==    Updates: 100* Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@56a4f272]* 100* 2018-10-02 15:08:03.928  INFO 7972 --- [       Thread-2] o.s.w.c.s.GenericWebApplicationContext   : Closing org.springframework.web.context.support.GenericWebApplicationContext@37313c65: startup date [Tue Oct 02 15:08:00 CST 2018]; root of context hierarchy* 2018-10-02 15:08:03.937  INFO 7972 --- [       Thread-2] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...* 2018-10-02 15:08:04.053  INFO 7972 --- [       Thread-2] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.** Process finished with exit code 0*/}

项目中的使用方式

    @Overridepublic List<User> getAllAdminUsers(){QueryWrapper<User> userQueryWrapper = new QueryWrapper<>();userQueryWrapper.eq(User.Fields.admin, "1");return list(userQueryWrapper);}