mybatis @Select 静态工厂关键字 sql 编译时出错？

Question

当我使用 @Select 时，它是带有代码的 ibatis 注释：

@Select({"SELECT ", selectField, " FROM ", table, "WHERE finished = #{finished}"})
 List<ToDo> listToDoByFinished(@Param("finished") Integer finished);

它工作正常并且可以编译通过，但是当我更改代码时：

//FIXME
@Select({SELECT, selectField, FROM, table, WHERE, finished, EQUAL, "#{finished}"})
 List<ToDo> listToDoByFinished(@Param("finished") Integer finished);

无法编译通过，错误信息为：

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.2:compile (default-compile) on project blog: Compilation failure
[ERROR] /home/freeze/my_project/lbfreeze-blog/src/main/java/me/freezehome/blog/dao/ToDoDAO.java:[32,54] 错误（error): 不兼容的类型(type mismatch): Integer无法转换为String(Interger cannot convert to String)
[ERROR] -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

在SqlFactory中定义的sql关键词：

package me.freezehome.blog.factory;

public  class SqlFactory {
    private SqlFactory(){}
    public static final  String SELECT = " SELECT ";
    public static final  String INSERT = " INSERT ";
    public static final  String UPDATE = " UPDATE ";
    public static final  String DELETE = " DELETE ";

    public static final  String WHERE = " WHERE ";
    public static final  String FROM = " FROM ";
    public static final  String AND = " AND ";
    public static final  String OR = " OR ";
    public static final  String IN = " IN ";
    public static final  String INTO = " INTO ";
    public static final  String VALUES = "VALUES";
    public static final  String EQUAL = " = ";


}

接口中定义的其他：

package me.freezehome.blog.dao;

import me.freezehome.blog.driver.MyInLanguageDriver;
import me.freezehome.blog.model.ToDo;
import org.apache.ibatis.annotations.*;

import java.util.List;

import static me.freezehome.blog.config.StringConfig.strSeparator;
import static me.freezehome.blog.factory.SqlFactory.*;

public interface ToDoDAO {
    String table = "todo";
    String id = "id";
    String title = "title";
    String content = "content";
    String finished = "finished";

    String selectField = id + strSeparator + title + strSeparator + content + strSeparator + finished;
    String insertField = title + strSeparator + content;
}

其他信息：

mybatis 3.4.1
mybatis-spring1.3.0
spring 4.3.3
mavne 3.3.9
java "1.8.0_111" Java(TM) SE 运行时环境（build 1.8.0_111-b14） Java HotSpot(TM) 64 位服务器 VM（内部版本 25.111-b14，混合模式）

Answer 1

我猜你有 import static SqlFactory。*

在 ToDoDAO 接口中，所有 String 都应为 static final，因为注释需要常量参数。

Answer 2

我已经在我的小应用程序上试过这段代码。结果，Java 编译器将尝试引用与常量同名的方法参数。

在这种情况下，Java 编译将尝试引用方法参数（finished 定义为 Integer）而不是 String finished = "finished";（常量）。因此在编译时发生类型转换错误。

我不知道它是否是 Java 编译器的规范。

也许您可以通过将常量名称转换为大写来解决此问题。

mybatis @Select 静态工厂关键字 sql 编译时出错？

mybatis @Select with a static factory of sql keyword get a error when compile?

java

spring

compiler-errors

mybatis