Kotlin 实战小记：No-Arg 引用解决 No constructor found的问题

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一、问题

新的项目试用一下kotlin, 调用数据库查询数据的时候报了这个问题：org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.executor.ExecutorException: No constructor found in com.neusoft.collect.entity.cm.CmRoom matching [java.lang.String, java.lang.String, java.lang.String, java.lang.Integer, java.lang.String, java.lang.Double, java.lang.Double]

二、原因

因为使用的是kotlin data class，通过mybatis查询返回不是data class中全部的字段，kotlin创建对象本身是没有无参构造器的，Java默认包含无参构造器；data class 是要返回所有字段，而业务不需要返回所有字段，这是问题出现的所在。

三、处理办法

通过引用No-Arg 插件，官网地址：No-arg compiler plugin | Kotlin Documentation

四、工程样例

注意：  <option>no-arg:annotation=com.neusoft.collect.config.NoArg</option> 和 创建的annotation class 路径保持一致

1、maven 部分引包

   <properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><maven.compiler.source>${java.version}</maven.compiler.source><maven.compiler.target>${java.version}</maven.compiler.target><springfox.swagger3.version>3.0.0</springfox.swagger3.version><kotlin.version>2.0.0</kotlin.version></properties><dependencies><dependency><groupId>org.jetbrains.kotlin</groupId><artifactId>kotlin-maven-noarg</artifactId><version>${kotlin.version}</version></dependency></dependencies><build><plugins><plugin><artifactId>kotlin-maven-plugin</artifactId><groupId>org.jetbrains.kotlin</groupId><version>${kotlin.version}</version><configuration><compilerPlugins> <!-- Or "jpa" for JPA support --><plugin>no-arg</plugin></compilerPlugins><pluginOptions><option>no-arg:annotation=com.neusoft.collect.config.NoArg</option><!-- Call instance initializers in the synthetic constructor --><!-- <option>no-arg:invokeInitializers=true</option> --></pluginOptions> </configuration></plugin></plugins></build>

2、创建 annotation class

package com.neusoft.collect.config/*** @author zc* @date 2024/06/18 10:31* @desc*/
annotation class NoArg

3、data class 样例 引用 annotation class NoArg

package com.neusoft.collect.entity.cmimport com.neusoft.collect.config.NoArg
import java.io.Serializable/*** @author zc* @date 2024/06/05 16:33* @desc 机房*/
@NoArg
data class CmRoom(/*** 多云统一名称*/var mc_uniform_name: String,/*** 详细地址*/var detailed_address: String,/*** 机楼名称*/var building_name: String,/*** 机房所在楼层*/var floor: Int,/*** 机房房间号*/var room_num: String,/*** 机房总行数*/var row_count: Int?,/*** 机房总列数*/var column_count: Int?,/*** 规划机架数*/var project_rack_count: Int?,/*** 占用机架数*/var occupation_rack_count: Int?,/*** 共用情况 枚举值：仅省级云使用、与其他业务共用*/val share_statistic: String = "仅省级云使用",/*** 机房数据维护责任人*/val data_maintain_vendor: String = "李剑春",/*** 关联资源池节点*/var rel_res_pool_id: String,/*** 所属数据中心*/val rel_dc_id: String = "JX001CPC-RP-JX-01",/*** 资源ID*/var resource_id: String
): Serializable

4、mapper 样例： 返回部分字段

 /*** Room* 机房* @return*/@Select("SELECT  name AS mc_uniform_name," +" address AS detailed_address," +" building_name," +" floor," +" '001' AS room_num," +" CONCAT(#{province}, '004', pool_alias) AS rel_res_pool_id," +" CONCAT(#{province}, '002', instance_id) AS resource_id" +" FROM cm_room_t")@Results(Result(property = "mc_uniform_name", column = "mc_uniform_name"),Result(property = "detailed_address", column = "detailed_address"),Result(property = "building_name", column = "building_name"),Result(property = "room_num", column = "room_num"),Result(property = "rel_res_pool_id", column = "rel_res_pool_id"),Result(property = "resource_id", column = "resource_id"))fun room(province: String): List<CmRoom>

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