注明：上篇文章介绍了springboot+mybatis-plus通用CRUD的用法，这篇文章我们来介绍一下mybatis-plus强大的条件构造器。mybatis-plus的版本为最新版3.0.3  。条件构造器咱们讲述queryWrapper和updateWrapper的用法、关系、以及强大之处。
首先在这里写下官方文档的链接位置，官方文档说的很详细。如果还想知道在项目中的具体用法请往下看。
一、条件构造器关系介绍

介绍 ：

上图绿色框为抽象类abstract
蓝色框为正常class类，可new对象
黄色箭头指向为父子类关系，箭头指向为父类

wapper介绍 ：

Wrapper ：  条件构造抽象类，最顶端父类，抽象类中提供4个方法西面贴源码展示
AbstractWrapper ： 用于查询条件封装，生成 sql 的 where 条件
AbstractLambdaWrapper ： Lambda 语法使用 Wrapper统一处理解析 lambda 获取 column。
LambdaQueryWrapper ：看名称也能明白就是用于Lambda语法使用的查询Wrapper
LambdaUpdateWrapper ： Lambda 更新封装Wrapper
QueryWrapper ： Entity 对象封装操作类，不是用lambda语法
UpdateWrapper ：  Update 条件封装，用于Entity对象更新操作

二、项目实例
在这里我以QueryWrapper和UpdateWrapper为例，进行测试讲解。我会在上篇博客原有的基础上进行测试，如果不喜欢搭建项目的可直接下载我上个项目，上个项目的博客对应上个项目的讲解


上图表格为条件构造器使用中的各个方法格式和说明，如有不懂可参考官方文档内容
构造器条件
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 {

    @Autowired
    private 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>
     */
    @Test
    public 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>
     */
    @Test
    public 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
     */
    @Test
    public 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
     */
    @Test
    public 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）
     */
    @Test
    public 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）
     */
    @Test
    public 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
     */
    @Test
    public 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）
     */
    @Test
    public void update() {

        //修改值
        User user = new User();
        user.setStatus(true);
        user.setName("zhangsan");

        //修改条件s
        UpdateWrapper<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
     */

}


上方代码对通过构造器条件进行的查询、删除、修改进行是演示，构造器方法没有做过多演示，但是所有的构造器方法同理使用，如果还有不会用的点开看官方文档查看并按照上方例子使用即可。
源码下载地址
上一篇 ：（四） springboot + mybatis plus详细拆解CRUD

下一篇 ： （六）springboot + mybatis plus实现多表联查分页3.X版本

官方文档：https://mp.baomidou.com/guide/wrapper.html#querywrapper

select("id", "name", "age")

select(i -> i.getProperty().startsWith("test"))

controller中使用的例子



 

QueryWrapper用法1：
   public IPage<EvaluateInfoBaseInfoIdVO> initAppEvaluateInfoBaseInfoIdVO(String elderId){
        List<EvaluateInfoBaseInfoIdVO> evaluateInfoBaseInfoIdVOList = new ArrayList<EvaluateInfoBaseInfoIdVO>();
        QueryWrapper<EvaluateBaseInfo> queryWrapper = new QueryWrapper<EvaluateBaseInfo>();
        queryWrapper.eq("del_flag",0);
        queryWrapper.eq("elder_id",elderId);
        List<EvaluateBaseInfo> evaluateBaseInfoList = this.baseMapper.selectList(queryWrapper);
        //处理一个老人多次评估
        for (EvaluateBaseInfo base :evaluateBaseInfoList){
            evaluateInfoBaseInfoIdVOList.add(this.initOne(base.getId()));
        }
        Page<EvaluateInfoBaseInfoIdVO> page = new Page<EvaluateInfoBaseInfoIdVO>();
        page.setRecords(evaluateInfoBaseInfoIdVOList);
        return page;
    }

用法2：
  List<SysUserRole> userRole = sysUserRoleService.list(new QueryWrapper<SysUserRole>().lambda().eq(SysUserRole::getUserId, userid));

 QueryWrapper查询方式案例



​​​​​​

 in参考下面红色标注字段，其他查询参考下面




public List<String> getNextNewsIdList(NewsSearchVo searchVo) throws ParseException {

    QueryWrapper<TbmNewsProcessing> qw = new QueryWrapper<>();

if (searchVo.getCreateDate() != null) {
    qw.ge("create_time", searchVo.getCreateDate());
}
if (searchVo.getCreateDateEnd() != null) {
    qw.le("create_time", DateUtil.parse(searchVo.getCreateDateEnd()).plusSeconds(24 * 60 * 60 - 1));
}
if (StringUtils.isNotBlank(searchVo.getNewsType()) && searchVo.getNewsType().contains(",")) {
    //此处最好是List入参，in才更为精准
    List<String>  newsTypes=Arrays.asList(searchVo.getNewsType().split(","));
    qw.in("news_type", newsTypes);
} else if (StringUtils.isNotBlank(searchVo.getNewsType()) && !searchVo.getNewsType().contains(",")) {
    qw.eq("news_type", searchVo.getNewsType());
}
if (StringUtils.isNotBlank(searchVo.getMediaSource())) {
    qw.eq("media_source_code", searchVo.getMediaSource());
}
if (StringUtils.isNotBlank(searchVo.getAuthor())) {
    qw.eq("author", searchVo.getAuthor());
}
if (CollectionUtils.isNotEmpty(searchVo.getTagIds()) && searchVo.getTagIds().size() == 2) {
    if (StringUtils.isNotBlank(searchVo.getTagIds().get(0)) || StringUtils.isNotBlank(searchVo.getTagIds().get(1))) {
        
        qw.inSql("news_id", "SELECT DISTINCT(news_id) FROM tbm_news_tags WHERE register_tag_id in (" + registerTagIds + ")");
    }
}
if (searchVo.getAreaCode() != null) {
    qw.inSql("news_id", "SELECT DISTINCT(news_id) FROM tbm_news_area_tags WHERE business_id = " + searchVo.getAreaCode());
}

if (searchVo.getAppIds() != null) {
    if (searchVo.getAppIds().equals("2")) {
        qw.orderByDesc("priority");
    } else if (searchVo.getAppIds().equals("3")) {
        qw.orderByDesc("xf_priority");
    } else if (searchVo.getAppIds().equals("5")) {
        qw.orderByDesc("yq_priority");
    } else if (searchVo.getAppIds().equals("6")) {
        qw.orderByDesc("jyp_priority");
    }
}
qw.orderByDesc("create_time")
        .eq("handle_status", 0)
        .notInSql("news_id", "select news_id from tbm_discard_task where discard_user_id=" + searchVo.getSessionUserId())
        .last("limit  100");
qw.select("    news_id    ");
List<TbmNewsProcessing> newsIdObjectList = processingMapper.selectList(qw);

 public List<String> getNextNewsIdList(NewsSearchVo searchVo) throws ParseException {
        QueryWrapper<TbmNewsProcessing> qw = new QueryWrapper<>();
        if (StringUtils.isNotBlank(searchVo.getNewsId())) {
            qw.like("news_id", SqlUtil.escapeLike(searchVo.getNewsId().trim()));
        }
        if (StringUtils.isNotBlank(searchVo.getAppIds())) {
            qw.like("app_ids", searchVo.getAppIds());
        }
        if (StringUtils.isNotBlank(searchVo.getTitle())) {
            qw.like("title", SqlUtil.escapeLike(searchVo.getTitle().trim()));
        }
        if (StringUtils.isNotBlank(searchVo.getDsNewsColumns())) {
            qw.eq("ds_news_columns", SqlUtil.escapeLike(searchVo.getDsNewsColumns().trim()));
        }
        if (searchVo.getUpdateTime() != null) {
            qw.ge("update_time", searchVo.getUpdateTime());
        }
        if (searchVo.getUpdateTimeEnd() != null) {
            qw.le("update_time", DateUtil.parse(searchVo.getUpdateTimeEnd()).plusSeconds(24 * 60 * 60 - 1));
        }
        if (searchVo.getCreateDate() != null) {
            qw.ge("create_time", searchVo.getCreateDate());
        }
        if (searchVo.getCreateDateEnd() != null) {
            qw.le("create_time", DateUtil.parse(searchVo.getCreateDateEnd()).plusSeconds(24 * 60 * 60 - 1));
        }
        if (searchVo.getPublishDate() != null) {
            qw.ge("src_publish_date", searchVo.getPublishDate());
        }
        if (searchVo.getPublishDateEnd() != null) {
            qw.le("src_publish_date", DateUtil.parse(searchVo.getPublishDateEnd()).plusSeconds(24 * 60 * 60 - 1));
        }
        if (searchVo.getPublishStatus() != null) {
            qw.eq("publish_status", searchVo.getPublishStatus());
        }
        if (searchVo.getDsSourceType() != null) {
            qw.eq("ds_source_type", searchVo.getDsSourceType());
        }
        if (searchVo.getLevel() != null) {
            qw.eq("level", searchVo.getLevel());
        }
        if (StringUtils.isNotBlank(searchVo.getNewsUrl())) {
            qw.like("news_url", SqlUtil.escapeLike(searchVo.getNewsUrl().trim()));
        }
        if (StringUtils.isNotBlank(searchVo.getAuthorOrgCode())) {
            qw.eq("author_org_code", searchVo.getAuthorOrgCode());
        }
        if (searchVo.getRange() != null) {
            qw.eq("range_base", searchVo.getRange());
        }
        if (searchVo.getRangePlus() != null) {
            qw.eq("range_plus", searchVo.getRangePlus());
        }
        if (searchVo.getFinancial() != null) {
            qw.eq("financial", searchVo.getFinancial());
        }
        if (searchVo.getFinancialPlus() != null) {
            qw.eq("financial_plus", searchVo.getFinancialPlus());
        }
        if (StringUtils.isNotBlank(searchVo.getNewsType()) && searchVo.getNewsType().contains(",")) {
            List<String>  newsTypes=Arrays.asList(searchVo.getNewsType().split(","));
            qw.in("news_type", newsTypes);
        } else if (StringUtils.isNotBlank(searchVo.getNewsType()) && !searchVo.getNewsType().contains(",")) {
            qw.eq("news_type", searchVo.getNewsType());
        }
        if (StringUtils.isNotBlank(searchVo.getMediaSource())) {
            qw.eq("media_source_code", searchVo.getMediaSource());
        }
        if (StringUtils.isNotBlank(searchVo.getAuthor())) {
            qw.eq("author", searchVo.getAuthor());
        }
        if (CollectionUtils.isNotEmpty(searchVo.getTagIds()) && searchVo.getTagIds().size() == 2) {
            if (StringUtils.isNotBlank(searchVo.getTagIds().get(0)) || StringUtils.isNotBlank(searchVo.getTagIds().get(1))) {
                String registerTagIds = "";
                if (StringUtils.isNotBlank(searchVo.getTagIds().get(0))) {
                    registerTagIds = registerTagIds + "\"" + searchVo.getTagIds().get(0) + "\"";
                }
                if (StringUtils.isNotBlank(searchVo.getTagIds().get(0)) && StringUtils.isNotBlank(searchVo.getTagIds().get(1))) {
                    registerTagIds = registerTagIds + ",";
                }
                if (StringUtils.isNotBlank(searchVo.getTagIds().get(1))) {
                    registerTagIds = registerTagIds + "\"" + searchVo.getTagIds().get(1) + "\"";
                }
                qw.inSql("news_id", "SELECT DISTINCT(news_id) FROM tbm_news_tags WHERE register_tag_id in (" + registerTagIds + ")");
            }
        }
        if (searchVo.getAreaCode() != null) {
            qw.inSql("news_id", "SELECT DISTINCT(news_id) FROM tbm_news_area_tags WHERE business_id = " + searchVo.getAreaCode());
        }


        if (searchVo.getAppIds() != null) {
            if (searchVo.getAppIds().equals("2")) {
                qw.orderByDesc("priority");
            } else if (searchVo.getAppIds().equals("3")) {
                qw.orderByDesc("xf_priority");
            } else if (searchVo.getAppIds().equals("5")) {
                qw.orderByDesc("yq_priority");
            } else if (searchVo.getAppIds().equals("6")) {
                qw.orderByDesc("jyp_priority");
            }
        }
        qw.orderByDesc("create_time")
                .eq("handle_status", 0)
                .notInSql("news_id", "select news_id from tbm_discard_task where discard_user_id=" + searchVo.getSessionUserId())
                .last("limit  100");
        qw.select("    news_id    ");
        List<TbmNewsProcessing> newsIdObjectList = processingMapper.selectList(qw);

        List<String> newsIdList = new ArrayList<String>();
        if (newsIdObjectList != null && !newsIdObjectList.isEmpty()) {
            newsIdObjectList.forEach(item -> {
                newsIdList.add(String.valueOf(item.getNewsId()));
            });
        }
        return newsIdList;
    }