【Mybatis】Mybatis-generator插件Cannot instantiate object of type...

使用mybatis-generator插件自动生成代码，遇到了这么一个问题，当使用自定义的类型转换类时，启动插件始终实例化不了相应的转换类，报错如下：

[ERROR] Failed to execute goal org.mybatis.generator:mybatis-generator-maven-plugin:1.3.5:generate (default-cli) on project test-dao: Execution default-cli of goal org.mybatis.generator:mybatis-generator-maven-plugin:1.3.5:generate failed: Cannot instantiate object of type com.example.test.common.utils.MyJavaTypeResolverDefaultImpl -> [Help 1]

如何解决呢？度娘中的帖子虽然和上边报错一样，但发现解决方法并不完全适用，故这里记录一下自己如何解决的，希望对某些撸友有用

步骤一：自定义的转换类作为另外一个项目打包引用

之所以如此做，据说是目前mybatis-generator插件还存在应用上的bug，话不多说，能用就行，代码如下：

<plugin>
    <groupId>org.mybatis.generator</groupId>
    <artifactId>mybatis-generator-maven-plugin</artifactId>
    <version>1.3.5</version>
    <configuration>
        <configurationFile>${basedir}/src/main/resources/generatorConfig.xml</configurationFile>
        <overwrite>true</overwrite>
        <verbose>true</verbose>
    </configuration>
    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>${mysql.connector.version}</version>
        </dependency>
        <dependency>
            <groupId>tk.mybatis</groupId>
            <artifactId>mapper</artifactId>
            <version>${tk.mybatis.version}</version>
        </dependency>
        <dependency>
            <groupId>com.example</groupId>
            <artifactId>test-common</artifactId>
            <version>${pro.version}</version>
        </dependency>
    </dependencies>
</plugin>

其中test-common作为一个公用module项目被插件引用

步骤二：更换打包插件maven-jar-plugin

Springboot的maven项目创建时，默认使用的是spring-boot-maven-plugin插件，实验发现该插件在打包编译时有时会出现莫名其妙的错误，百思不得姐...

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <mainClass>com.example.test.web.WebApplication</mainClass>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>repackage</goal>
            </goals>
        </execution>
    </executions>
</plugin>

最后更换为maven-jar-plugin插件，发现一切都正常了，ok，问题变相搞定了，汗颜

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-jar-plugin</artifactId>
    <version>2.3.1</version>
    <configuration>
        <archive>
            <manifestEntries>
                <Main-Class>
                    com.example.test.web.WebApplication
                </Main-Class>
                <Class-Path>config/</Class-Path>
            </manifestEntries>
        </archive>
        <excludes>
            <exclude>*.sh</exclude>
            <exclude>*.conf</exclude>
            <exclude>*.properties</exclude>
            <exclude>*.xml</exclude>
            <exclude>*.yml</exclude>
        </excludes>
    </configuration>
</plugin>

总结：

mybatis-generator插件由于自身的缺陷，一些类型转换自定义的类需要作为jar包引用；另spring-boot-maven-plugin插件也存在一些莫名其妙的问题（能力不够原因也没找到），替换为maven-jar-plugin插件即可。