no main manifest attribute, in mybatis-generator-core-2.3.0.jar

The error message "no main manifest attribute" typically occurs when you try to execute a JAR file that doesn't have a proper entry point defined in its manifest. In the case of the `mybatis-generator-core-2.3.0.jar`, it seems that the JAR file is meant to be used as a library and not as a standalone executable.

To resolve this issue, you need to use the `mybatis-generator-core-2.3.0.jar` as a dependency in your project rather than trying to execute it directly. Make sure to include it in your project's build path or add it as a dependency in your build tool configuration (e.g., Maven or Gradle).

If you are using Maven, you can add the following dependency to your `pom.xml` file:

<dependency>
    <groupId>org.mybatis.generator</groupId>
    <artifactId>mybatis-generator-core</artifactId>
    <version>2.3.0</version>
</dependency>

If you are using Gradle, you can add the following dependency to your `build.gradle` file:

dependencies {
    implementation 'org.mybatis.generator:mybatis-generator-core:2.3.0'
}

Remember to replace any existing conflicting dependencies with the appropriate version of `mybatis-generator-core`.

Once you have added the dependency correctly, you should be able to use the functionality provided by `mybatis-generator-core` in your project without encountering the "no main manifest attribute" error.