从零搭建开发脚手架 Spring Boot集成Mybatis-plus之二

桃扇骨 2022-10-23 08:24 432阅读 0赞

### 文章目录 ###

*  分页查询
 *   *  普通分页
 *  自动填充新建时间、更新时间、操作人等属性
 *  自定义字段类型
 *   *  自动映射Json数据
     *  自动映射空间数据格式
 *  自定义Controller模板
 *   *  自定义代码模板
     *  自定义属性注入
     *  框架自带的可用参数
     *  模板修改
 *  数据权限实现
 *  Lambda条件构造器
 *   *  通用Wrapper
     *  QueryWrapper
     *  UpdateWrapper
 *  枚举字段
 *   *  1.声明枚举
     *  2.配置扫描枚举
     *  3.使用示例
     *  4.前端JSON
 *  实战经验总结lambda查询、更新、模糊查询等示例
 *   *  lambda查询
     *  lambda更新
     *  自定义sql 注解@select+like
     *  自定义结果映射 驼峰命名自动映射
     *  自定义sql分页

接上篇  
[《从零搭建开发脚手架 Spring Boot集成Mybatis-plus之一》][Spring Boot_Mybatis-plus]

# 分页查询 #

**首先配置分页插件**

/** * 新的分页插件,一缓和二缓遵循mybatis的规则,需要设置 MybatisConfiguration#useDeprecatedExecutor = false 避免缓存出现问题(该属性会在旧插件移除后一同移除) */
        @Bean
        public MybatisPlusInterceptor mybatisPlusInterceptor() { 
            MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
            interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.MYSQL));
            return interceptor;
        }
    
        @Bean
        public ConfigurationCustomizer configurationCustomizer() { 
            return configuration -> configuration.setUseDeprecatedExecutor(false);
        }

## 普通分页 ##

分页查询代码示例

@GetMapping
        public Response pageAll(@RequestParam(required = false, defaultValue = "1") long current,
                                @RequestParam(required = false, defaultValue = "10") long size,
                                String roadName) { 
            Page roadPage = new Page<>(current, size);
            LambdaQueryWrapper<Road> queryWrapper = new QueryWrapper().lambda();
            queryWrapper.like(StringUtils.isNotBlank(roadName), Road::getRoadName, roadName);
            Page pageList = roadService.page(roadPage, queryWrapper);
            return Response.ok(pageList);
        }

# 自动填充新建时间、更新时间、操作人等属性 #

*  **首先**，实现元对象处理器接口：`com.baomidou.mybatisplus.core.handlers.MetaObjectHandler`

@Slf4j
    @Component
    public class MyMetaObjectHandler implements MetaObjectHandler { 
        @Override
        public void insertFill(MetaObject metaObject) {  // Mapper调用insert操作时，进行如下操作
            log.info("start insert fill ...."); // 给entity的属性设置值
            this.strictInsertFill(metaObject, "createTime", () -> LocalDateTime.now(), LocalDateTime.class);
            this.strictInsertFill(metaObject, "operator", String.class, "张三");
        }
        @Override
        public void updateFill(MetaObject metaObject) { // Mapper调用update操作时，进行如下操作
            log.info("start update fill ...."); // 给entity的属性设置值
            this.strictUpdateFill(metaObject, "updateTime", () -> LocalDateTime.now(), LocalDateTime.class);
            this.strictUpdateFill(metaObject, "operator", String.class, "张三");
        }
    }

> `MetaObjectHandler`提供的默认方法的策略均为：
> 
>  *  如果属性有值则不覆盖。
>  *  如果填充值为`null`则不填充。

*  **其次**，给相应实体类设置注解

> 注解：指定该属性在**对应情况下必有值**，如果无值则入库会是`null`
> 
> 字段必须声明`TableField`注解,属性`fill`选择对应策略,该声明告知`Mybatis-Plus`需要预留注入`SQL`字段
> 
> 原理：判断注入的 insert 和 update 的 sql 脚本是否在对应情况下忽略掉字段的 if 标签生成  
> …

@Data
    @EqualsAndHashCode(callSuper = false)
    public class Stake implements Serializable { 
        private Long roadId;
        private String stakeName;
    
        @TableField(fill = FieldFill.INSERT)
        @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
        private LocalDateTime createTime;
    
        @TableField(fill = FieldFill.UPDATE)
        @JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
        private LocalDateTime updateTime;
    
        @TableField(fill = FieldFill.INSERT_UPDATE)
        private String operator;
    
    }

**整体原理**

*  当发生`insert`或者`update`的**sql**脚本时候
 *  看下当前发生相关**sql** 的实体中相应字段的注解
    
     *  注解`FieldFill.INSERT`，即动态添加`<if test="...">......</if>`insert相关字段
     *  注解`FieldFill.UPDATE`，即动态添加`<if test="...">......</if>`update相关字段
     *  注解`FieldFill.UPDATE`，即动态添加`<if test="...">......</if>`insert和update相关字段

# 自定义字段类型 #

类型处理器，用于 JavaType 与 JdbcType 之间的转换，用于 PreparedStatement 设置参数值和从 ResultSet 或 CallableStatement 中取出一个值，本文讲解 `mybaits-plus` 内置常用类型处理器如何通过`TableField`注解快速注入到 `mybatis` 容器中。

> 如果报xml中五自定义handler的错误，把xml删除，或者在xml中也配置上

## 自动映射Json数据 ##

@Data
    @Accessors(chain = true)
    @TableName(autoResultMap = true)
    public class User { 
        private Long id;
    
        /** * 注意！！ 必须开启映射注解 * * @TableName(autoResultMap = true) * * 以下两种类型处理器，二选一 也可以同时存在 * * 注意！！选择对应的 JSON 处理器也必须存在对应 JSON 解析依赖包 */
        @TableField(typeHandler = JacksonTypeHandler.class)
        // @TableField(typeHandler = FastjsonTypeHandler.class)
        private OtherInfo otherInfo;
    
    }

该注解对应了 XML 中写法为

## 自动映射空间数据格式 ##

可以看我的另一篇很详细 [从零搭建开发脚手架 mybatis自定义字段类型 以Mysql空间数据存储为例][mybatis_ _Mysql]

@Data
    @EqualsAndHashCode(callSuper = false)
    @TableName( autoResultMap = true)
    public class ServiceArea implements Serializable { 
        @TableId(value = "id", type = IdType.AUTO)
        private Integer id;
    
        /** * 经纬度 格式：X,Y */
        @TableField(typeHandler = JacksonTypeHandler.class)
        private double[] location;
    
        @TableField(typeHandler = GeoPointTypeHandler.class)
        private GeoPoint coordinate;
    
    }

# 自定义Controller模板 #

## 自定义代码模板 ##

//指定自定义模板路径, 位置：/resources/templates/entity2.java.ftl(或者是.vm)
    //注意不要带上.ftl(或者是.vm), 会根据使用的模板引擎自动识别
    TemplateConfig templateConfig = new TemplateConfig()
        .setEntity("templates/entity2.java");
    
    AutoGenerator mpg = new AutoGenerator();
    //配置自定义模板
    mpg.setTemplate(templateConfig);

![20210324150255605.png][]

## 自定义属性注入 ##

InjectionConfig injectionConfig = new InjectionConfig() { 
        //自定义属性注入:abc
        //在.ftl(或者是.vm)模板中，通过${cfg.abc}获取属性
        @Override
        public void initMap() { 
            Map<String, Object> map = new HashMap<>();
            map.put("abc", this.getConfig().getGlobalConfig().getAuthor() + "-mp");
            this.setMap(map);
        }
    };
    AutoGenerator mpg = new AutoGenerator();
    //配置自定义属性注入
    mpg.setCfg(injectionConfig);

entity2.java.ftl
    自定义属性注入abc=${cfg.abc}
    
    entity2.java.vm
    自定义属性注入abc=$!{cfg.abc}

## 框架自带的可用参数 ##

[Github ][Github]AbstractTemplateEngine 类中方法 getObjectMap 返回 objectMap 的所有值都可用。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FidTkzNTAwOTA2Ng_size_16_color_FFFFFF_t_70][]

/** * 渲染对象 MAP 信息 * * @param tableInfo 表信息对象 * @return ignore */
        public Map<String, Object> getObjectMap(TableInfo tableInfo) { 
            Map<String, Object> objectMap;
            ConfigBuilder config = getConfigBuilder();
            if (config.getStrategyConfig().isControllerMappingHyphenStyle()) { 
                objectMap = CollectionUtils.newHashMapWithExpectedSize(33);
                objectMap.put("controllerMappingHyphenStyle", config.getStrategyConfig().isControllerMappingHyphenStyle());
                objectMap.put("controllerMappingHyphen", StringUtils.camelToHyphen(tableInfo.getEntityPath()));
            } else { 
                objectMap = CollectionUtils.newHashMapWithExpectedSize(31);
            }
            objectMap.put("restControllerStyle", config.getStrategyConfig().isRestControllerStyle());
            objectMap.put("config", config);
            objectMap.put("package", config.getPackageInfo());
            GlobalConfig globalConfig = config.getGlobalConfig();
            objectMap.put("author", globalConfig.getAuthor());
            objectMap.put("idType", globalConfig.getIdType() == null ? null : globalConfig.getIdType().toString());
            objectMap.put("logicDeleteFieldName", config.getStrategyConfig().getLogicDeleteFieldName());
            objectMap.put("versionFieldName", config.getStrategyConfig().getVersionFieldName());
            objectMap.put("activeRecord", globalConfig.isActiveRecord());
            objectMap.put("kotlin", globalConfig.isKotlin());
            objectMap.put("swagger2", globalConfig.isSwagger2());
            objectMap.put("date", new SimpleDateFormat("yyyy-MM-dd").format(new Date()));
            objectMap.put("table", tableInfo);
            objectMap.put("enableCache", globalConfig.isEnableCache());
            objectMap.put("baseResultMap", globalConfig.isBaseResultMap());
            objectMap.put("baseColumnList", globalConfig.isBaseColumnList());
            objectMap.put("entity", tableInfo.getEntityName());
            objectMap.put("entitySerialVersionUID", config.getStrategyConfig().isEntitySerialVersionUID());
            objectMap.put("entityColumnConstant", config.getStrategyConfig().isEntityColumnConstant());
            objectMap.put("entityBuilderModel", config.getStrategyConfig().isEntityBuilderModel());
            objectMap.put("chainModel", config.getStrategyConfig().isChainModel());
            objectMap.put("entityLombokModel", config.getStrategyConfig().isEntityLombokModel());
            objectMap.put("entityBooleanColumnRemoveIsPrefix", config.getStrategyConfig().isEntityBooleanColumnRemoveIsPrefix());
            objectMap.put("superEntityClass", getSuperClassName(config.getStrategyConfig().getSuperEntityClass()));
            objectMap.put("superMapperClassPackage", config.getStrategyConfig().getSuperMapperClass());
            objectMap.put("superMapperClass", getSuperClassName(config.getStrategyConfig().getSuperMapperClass()));
            objectMap.put("superServiceClassPackage", config.getStrategyConfig().getSuperServiceClass());
            objectMap.put("superServiceClass", getSuperClassName(config.getStrategyConfig().getSuperServiceClass()));
            objectMap.put("superServiceImplClassPackage", config.getStrategyConfig().getSuperServiceImplClass());
            objectMap.put("superServiceImplClass", getSuperClassName(config.getStrategyConfig().getSuperServiceImplClass()));
            objectMap.put("superControllerClassPackage", verifyClassPacket(config.getStrategyConfig().getSuperControllerClass()));
            objectMap.put("superControllerClass", getSuperClassName(config.getStrategyConfig().getSuperControllerClass()));
            return Objects.isNull(config.getInjectionConfig()) ? objectMap : config.getInjectionConfig().prepareObjectMap(objectMap);
        }

## 模板修改 ##

*  `${table.serviceName?substring(1)}` \- 删除首字母
 *  `${table.serviceName?uncap_first}` \- 首字母大写变小写

package ${ package.Controller};
    
    import org.springframework.web.bind.annotation.RequestMapping;
    import ${ package.Entity}.${ entity};
    import ${ package.Service}.${ table.serviceName};
    <#if restControllerStyle>
    import org.springframework.web.bind.annotation.RestController;
    <#else>
    import org.springframework.stereotype.Controller;
    </#if>
    import com.laker.map.ext.framework.Response;
    import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
    import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
    import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
    import io.swagger.annotations.ApiOperation;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.web.bind.annotation.*;
    <#if superControllerClassPackage??>
    import ${ superControllerClassPackage};
    </#if>
    
    /** * <p> * ${table.comment!} 前端控制器 * </p> * * @author ${author} * @since ${date} */
    <#if restControllerStyle>
    @RestController
    <#else>
    @Controller
    </#if>
    @RequestMapping("<#if package.ModuleName?? && package.ModuleName != "">/${package.ModuleName}</#if>/<#if controllerMappingHyphenStyle??>${controllerMappingHyphen}<#else>${table.entityPath}</#if>")
    <#if superControllerClass??>
    public class ${ table.controllerName} extends ${ superControllerClass} { 
    <#else>
    public class ${ table.controllerName} { 
    </#if>
        @Autowired
        ${ table.serviceName} ${ table.serviceName?substring(1)?uncap_first};
    
        @GetMapping
        @ApiOperation(value = "${table.comment!}分页查询")
        public Response pageAll(@RequestParam(required = false, defaultValue = "1") long current,
                                @RequestParam(required = false, defaultValue = "10") long size) { 
            Page roadPage = new Page<>(current, size);
            LambdaQueryWrapper<${ table.entityName}> queryWrapper = new QueryWrapper().lambda();
            Page pageList = ${ table.serviceName?substring(1)?uncap_first}.page(roadPage, queryWrapper);
            return Response.ok(pageList);
        }
    
        @PostMapping
        @ApiOperation(value = "新增或者更新${table.comment!}")
        public Response saveOrUpdate(${ table.entityName} param) { 
            return Response.ok(${ table.serviceName?substring(1)?uncap_first}.saveOrUpdate(param));
        }
    
        @GetMapping("/{id}")
        @ApiOperation(value = "根据id查询${table.comment!}")
        public Response get(@PathVariable Long id) { 
            return Response.ok(${ table.serviceName?substring(1)?uncap_first}.getById(id));
        }
    
        @DeleteMapping("/{id}")
        @ApiOperation(value = "根据id删除${table.comment!}")
        public Response delete(@PathVariable Long id) { 
            return Response.ok(${ table.serviceName?substring(1)?uncap_first}.removeById(id));
        }
    }

# 数据权限实现 #

看我另一篇博文，很详细[从零搭建开发脚手架 基于Mybatis-Plus的数据权限实现][_Mybatis-Plus]

# Lambda条件构造器 #

[https://baomidou.com/guide/wrapper.html\#abstractwrapper][https_baomidou.com_guide_wrapper.html_abstractwrapper]

> QueryWrapper(**LambdaQueryWrapper**) 和 UpdateWrapper(**LambdaUpdateWrapper**) 的父类  
> 用于生成 sql 的 where 条件, entity 属性也用于生成 sql 的 where 条件  
> 注意: entity 生成的 where 条件与 使用各个 api 生成的 where 条件**没有任何关联行为**

建议使用**Lambda条件构造器**，当属性更改时，可以直接反应出来调用关系。不像**QueryWrapper**一样是静态字符串配置的

**Lambda条件构造器**:

Page roadPage = new Page<>(current, size);
            LambdaQueryWrapper<Board> queryWrapper = new QueryWrapper().lambda();
            queryWrapper.eq(roadId != null, Board::getRoadId, roadId);
            queryWrapper.eq(deptId != null, Board::getDeptId, deptId);
            Page pageList = boardService.page(roadPage, queryWrapper);

**普通条件构造器**:

Page roadPage = new Page<>(current, size);
            QueryWrapper<Board> queryWrapper = new QueryWrapper();
            queryWrapper.eq(roadId != null, "road_id", roadId);
            queryWrapper.eq(deptId != null, "dept_id", deptId);
            Page pageList = boardService.page(roadPage, queryWrapper);

## 通用Wrapper ##

<table> 
 <thead> 
  <tr> 
   <th>条件</th> 
   <th>解释</th> 
   <th>例子</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>allEq</td> 
   <td>全部相等</td> 
   <td>例1: <code>allEq({id:1,name:"老王",age:null})</code>—&gt;<code>id = 1 and name = '老王' and age is null</code> <br>例2: <code>allEq({id:1,name:"老王",age:null}, false)</code>—&gt;<code>id = 1 and name = '老王'</code></td> 
  </tr> 
  <tr> 
   <td>eq</td> 
   <td>等于 =</td> 
   <td>eq(“name”, “老王”)<code>---&gt;</code>name = ‘老王’</td> 
  </tr> 
  <tr> 
   <td>ne</td> 
   <td>不等于 &lt;&gt;</td> 
   <td>ne(“name”, “老王”)<code>---&gt;</code>name &lt;&gt; ‘老王’</td> 
  </tr> 
  <tr> 
   <td>gt</td> 
   <td>大于 &gt;</td> 
   <td>gt(“age”, 18)<code>---&gt;</code>age &gt; 18</td> 
  </tr> 
  <tr> 
   <td>ge</td> 
   <td>大于等于 &gt;=</td> 
   <td>ge(“age”, 18)<code>---&gt;</code>age &gt;= 18</td> 
  </tr> 
  <tr> 
   <td>lt</td> 
   <td>小于 &lt;</td> 
   <td>lt(“age”, 18)<code>---&gt;</code>age &lt; 18</td> 
  </tr> 
  <tr> 
   <td>le</td> 
   <td>小于等于 &lt;=</td> 
   <td>le(“age”, 18)<code>---&gt;</code>age &lt;= 18</td> 
  </tr> 
  <tr> 
   <td>between</td> 
   <td>BETWEEN 值1 AND 值2</td> 
   <td>between(“age”, 18, 30)<code>---&gt;</code>age between 18 and 30</td> 
  </tr> 
  <tr> 
   <td>notBetween</td> 
   <td>NOT BETWEEN 值1 AND 值2</td> 
   <td>notBetween(“age”, 18, 30)<code>---&gt;</code>age not between 18 and 30</td> 
  </tr> 
  <tr> 
   <td>like</td> 
   <td>LIKE ‘%值%’</td> 
   <td>like(“name”, “王”)<code>---&gt;</code>name like ‘%王%’</td> 
  </tr> 
  <tr> 
   <td>notLike</td> 
   <td>NOT LIKE ‘%值%’</td> 
   <td>notLike(“name”, “王”)<code>---&gt;</code>name not like ‘%王%’</td> 
  </tr> 
  <tr> 
   <td>likeLeft</td> 
   <td>LIKE ‘%值’</td> 
   <td>likeLeft(“name”, “王”)<code>---&gt;</code>name like ‘%王’</td> 
  </tr> 
  <tr> 
   <td>likeRight</td> 
   <td>LIKE ‘值%’</td> 
   <td>likeRight(“name”, “王”)<code>---&gt;</code>name like ‘王%’</td> 
  </tr> 
  <tr> 
   <td>isNull</td> 
   <td>字段 IS NULL</td> 
   <td>isNull(“name”)<code>---&gt;</code>name is null</td> 
  </tr> 
  <tr> 
   <td>isNotNull</td> 
   <td>字段 IS NOT NULL</td> 
   <td>isNotNull(“name”)<code>---&gt;</code>name is not null</td> 
  </tr> 
  <tr> 
   <td>in</td> 
   <td>字段 IN (value.get(0), value.get(1), …)</td> 
   <td>in(“age”,{1,2,3})<code>---&gt;</code>age in (1,2,3)</td> 
  </tr> 
  <tr> 
   <td>notIn</td> 
   <td>NOT IN (value.get(0), value.get(1), …)</td> 
   <td>notIn(“age”,{1,2,3})<code>---&gt;</code>age not in (1,2,3)</td> 
  </tr> 
  <tr> 
   <td>inSql</td> 
   <td>字段 IN ( sql语句 )</td> 
   <td>例: <code>inSql("age", "1,2,3,4,5,6")</code>—&gt;<code>age in (1,2,3,4,5,6)</code> <br>例: <code>inSql("id", "select id from table where id &lt; 3")</code>—&gt;<code>id in (select id from table where id &lt; 3)</code></td> 
  </tr> 
  <tr> 
   <td>notInSql</td> 
   <td>字段 NOT IN ( sql语句 )</td> 
   <td>例: <code>notInSql("age", "1,2,3,4,5,6")</code>—&gt;<code>age not in (1,2,3,4,5,6)</code> <br>例: <code>notInSql("id", "select id from table where id &lt; 3")</code>—&gt;<code>id not in (select id from table where id &lt; 3)</code></td> 
  </tr> 
  <tr> 
   <td>groupBy</td> 
   <td>分组：GROUP BY 字段, …</td> 
   <td>groupBy(“id”, “name”)<code>---&gt;</code>group by id,name</td> 
  </tr> 
  <tr> 
   <td>orderByAsc</td> 
   <td>排序：ORDER BY 字段, … ASC</td> 
   <td>orderByAsc(“id”, “name”)<code>---&gt;</code>order by id ASC,name ASC</td> 
  </tr> 
  <tr> 
   <td>orderByDesc</td> 
   <td>排序：ORDER BY 字段, … DESC</td> 
   <td>例: <code>orderByDesc("id", "name")</code>—&gt;<code>order by id DESC,name DESC</code></td> 
  </tr> 
  <tr> 
   <td>orderBy</td> 
   <td>排序：ORDER BY 字段, …</td> 
   <td>例: <code>orderBy(true, true, "id", "name")</code>—&gt;<code>order by id ASC,name ASC</code></td> 
  </tr> 
  <tr> 
   <td>having</td> 
   <td>HAVING ( sql语句 )</td> 
   <td>例: <code>having("sum(age) &gt; 10")</code>—&gt;<code>having sum(age) &gt; 10</code><br> 例: <code>having("sum(age) &gt; {0}", 11)</code>—&gt;<code>having sum(age) &gt; 11</code></td> 
  </tr> 
  <tr> 
   <td>func</td> 
   <td>func 方法(主要方便在出现if…else下调用不同方法能不断链)</td> 
   <td>例: <code>func(i -&gt; if(true) {i.eq("id", 1)} else {i.ne("id", 1)})</code></td> 
  </tr> 
  <tr> 
   <td>or 拼接or</td> 
   <td>主动调用<code>or</code>表示紧接着下一个<strong>方法</strong>不是用<code>and</code>连接!(不调用<code>or</code>则默认为使用<code>and</code>连接)</td> 
   <td>eq(“id”,1).or().eq(“name”,“老王”)<code>---&gt;</code>id = 1 or name = ‘老王’</td> 
  </tr> 
  <tr> 
   <td>OR 嵌套or</td> 
   <td></td> 
   <td>or(i -&gt; i.eq(“name”, “李白”).ne(“status”, “活着”))<code>---&gt;</code>or (name = ‘李白’ and status &lt;&gt; ‘活着’)</td> 
  </tr> 
  <tr> 
   <td>and</td> 
   <td>AND 嵌套</td> 
   <td>例: <code>and(i -&gt; i.eq("name", "李白").ne("status", "活着"))</code>—&gt;<code>and (name = '李白' and status &lt;&gt; '活着')</code></td> 
  </tr> 
  <tr> 
   <td>nested</td> 
   <td>正常嵌套 不带 AND 或者 OR</td> 
   <td>nested(i -&gt; i.eq(“name”, “李白”).ne(“status”, “活着”))<code>---&gt;</code>(name = ‘李白’ and status &lt;&gt; ‘活着’)</td> 
  </tr> 
  <tr> 
   <td>apply</td> 
   <td>拼接 sql,该方法可用于数据库<strong>函数</strong> 动态入参的<code>params</code>对应前面<code>applySql</code>内部的<code>{index}</code>部分.这样是不会有sql注入风险的,反之会有!</td> 
   <td>例: <code>apply("id = 1")</code>—&gt;<code>id = 1</code><br> 例: <code>apply("date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")</code>—&gt;<code>date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")</code><br> 例: <code>apply("date_format(dateColumn,'%Y-%m-%d') = {0}", "2008-08-08")</code>—&gt;<code>date_format(dateColumn,'%Y-%m-%d') = '2008-08-08'")</code></td> 
  </tr> 
  <tr> 
   <td>last</td> 
   <td>无视优化规则直接拼接到 sql 的最后 只能调用一次,多次调用以最后一次为准 有sql注入的风险,请谨慎使用</td> 
   <td><code>last("limit 1")</code></td> 
  </tr> 
  <tr> 
   <td>exists</td> 
   <td>拼接 EXISTS ( sql语句 )</td> 
   <td>例: <code>exists("select id from table where age = 1")</code>—&gt;<code>exists (select id from table where age = 1)</code></td> 
  </tr> 
  <tr> 
   <td>notExists</td> 
   <td>拼接 NOT EXISTS ( sql语句 )</td> 
   <td>例: <code>notExists("select id from table where age = 1")</code>—&gt;<code>not exists (select id from table where age = 1)</code></td> 
  </tr> 
 </tbody> 
</table>

## QueryWrapper ##

<table> 
 <thead> 
  <tr> 
   <th>类型</th> 
   <th>解释</th> 
   <th>例子</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>select</td> 
   <td>设置查询字段</td> 
   <td>例: <code>select("id", "name", "age")</code> <br>例: <code>select(i -&gt; i.getProperty().startsWith("test"))</code></td> 
  </tr> 
 </tbody> 
</table>

## UpdateWrapper ##

<table> 
 <thead> 
  <tr> 
   <th>类型</th> 
   <th>解释</th> 
   <th>例子</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>set</td> 
   <td>SQL SET 字段</td> 
   <td>例: <code>set("name", "老李头")</code><br>例: <code>set("name", "")</code>—&gt;数据库字段值变为<strong>空字符串</strong> <br>例: <code>set("name", null)</code>—&gt;数据库字段值变为<code>null</code></td> 
  </tr> 
  <tr> 
   <td>setSql</td> 
   <td>设置 SET 部分 SQL</td> 
   <td>例: <code>setSql("name = '老李头'")</code></td> 
  </tr> 
 </tbody> 
</table>

# 枚举字段 #

## 1.声明枚举 ##

方式一： 使用 @EnumValue 注解枚举属性 [完整示例][Link 1]

@Getter
    public enum GradeEnum { 
    
        PRIMARY(1, "小学"),  SECONDORY(2, "中学"),  HIGH(3, "高中");
    
        GradeEnum(int code, String descp) { 
            this.code = code;
            this.descp = descp;
        }
    
        @EnumValue//标记数据库存的值是code
        private final int code;
        //。。。
    }

方式二： 枚举属性，实现 IEnum 接口如下：

public enum AgeEnum implements IEnum<Integer> { 
        ONE(1, "一岁"),
        TWO(2, "二岁"),
        THREE(3, "三岁");
        
        private int value;
        private String desc;
        
        @Override
        public Integer getValue() { 
            return this.value;
        }
    }

## 2.配置扫描枚举 ##

mybatis-plus:
        # 支持统配符 * 或者 ; 分割
        typeEnumsPackage: com.baomidou.springboot.entity.enums

## 3.使用示例 ##

数据库实体使用：

public class User { 
        /** * 名字 * 数据库字段: name varchar(20) */
        private String name;
        
        /** * 年龄，IEnum接口的枚举处理 * 数据库字段：age INT(3) */
        private AgeEnum age;
            
            
        /** * 年级，原生枚举（带{@link com.baomidou.mybatisplus.annotation.EnumValue}): * 数据库字段：grade INT(2) */
        private GradeEnum grade;
    }

## 4.前端JSON ##

[https://mp.baomidou.com/guide/enum.html\#jackson][https_mp.baomidou.com_guide_enum.html_jackson]

# 实战经验总结lambda查询、更新、模糊查询等示例 #

## lambda查询 ##

Manager one = managerService.getOne(
                                 Wrappers.<Manager>lambdaQuery()
                                   .eq(loginDto.getUserNo() != null, Manager::getUserNo, loginDto.getUserNo()));

## lambda更新 ##

boolean update = managerService.update(Wrappers.<Manager>lambdaUpdate().eq(Manager::getUserNo, changePwdDto.getUserNo())
                    .eq(Manager::getPassWord, changePwdDto.getOldPwd())
                    .set(Manager::getPassWord, changePwdDto.getNewPwd()));

## 自定义sql 注解@select+like ##

@Select("SELECT\n" +
                "\t s.*,st.name student_name \n" +
                "FROM\n" +
                "\tt_sign s\n" +
                "\tINNER JOIN t_student st ON s.wxid = st.wx_id\n" +
                "\twhere s.time like CONCAT('%',#{date},'%')\n and s.course_id = #{courseId}" +
                "\t")
        List<Sign> selectByCourseIdAndDate(Long courseId, String date);

## 自定义结果映射 驼峰命名自动映射 ##

student\_name – studentName

@TableId(value = "id", type = IdType.AUTO)
        private Long id;
    
        private Long courseId;
    
        private String wxid;
    
        private String time;
    
        @TableField(exist = false)
        private String studentName;

## 自定义sql分页 ##

@Select("SELECT\n" +
                "\t c.*,cr.start_time record_start_time \n" +
                "FROM\n" +
                "\tt_course c\n" +
                "\tINNER JOIN t_course_record cr ON c.id = cr.course_id\n" +
                "\t where c.teacher_id = #{teacherId} order by start_time desc")
        Page<Course> selectByTeacherId(Page page, Long teacherId);

[Spring Boot_Mybatis-plus]: https://blog.csdn.net/abu935009066/article/details/114535661
[mybatis_ _Mysql]: https://blog.csdn.net/abu935009066/article/details/114943494
[20210324150255605.png]: /images/20221023/23b149a99f20496d91aaa6e05f00c06e.png
[Github]: https://github.com/baomidou/generator/blob/develop/mybatis-plus-generator/src/main/java/com/baomidou/mybatisplus/generator/engine/AbstractTemplateEngine.java
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FidTkzNTAwOTA2Ng_size_16_color_FFFFFF_t_70]: /images/20221023/810d4706d1614f849fbffe11bdd55d6d.png
[_Mybatis-Plus]: https://blog.csdn.net/abu935009066/article/details/115481149
[https_baomidou.com_guide_wrapper.html_abstractwrapper]: https://baomidou.com/guide/wrapper.html#abstractwrapper
[Link 1]: https://gitee.com/baomidou/mybatis-plus-samples/blob/master/mybatis-plus-sample-enum/src/main/java/com/baomidou/mybatisplus/samples/enums/enums/GradeEnum.java
[https_mp.baomidou.com_guide_enum.html_jackson]: https://mp.baomidou.com/guide/enum.html#jackson