mybatis 返回结果映射错误

[xufeng888]

About the Bug...

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of MyBatis.

• I have confirmed this bug reproduces without 3rd party extensions (e.g. mybatis-plus).

Database Version

Microsoft SQL Server 2016 (RTM) - 13.0.1601.5 (X64)

JDBC Driver Version

com.microsoft.sqlserver/12.4.2.jre11

Issue Description

SELECT TOP 1 CAST(J06A029 AS VARBINARY(MAX)) as imageData FROM J06A WHERE J06A001 = '123456'
byte[] selectImageDataByReceiptNo(String receiptNo);
java 开发中:用byte[]接收 报错:
'imageData' from result set. Cause: com.microsoft.sqlserver.jdbc.SQLServerException: 不支持从 varbinary 到 TINYINT 的转换

@select("SELECT TOP 1 CAST(J06A029 AS VARBINARY(MAX)) as imageData FROM J06A WHERE J06A001 = #{receiptNo}")
Object selectImageDataByReceiptNo(String receiptNo);
用 Object 接收 程序正常

About your report...

• I did not use images 🖼️ for showing text information (code, error, etc.).

• I checked the Preview and my report looks awesome! 👍

[harawata]

Hello @xufeng888 ,

There is not enough information to understand your problem.
Please create a small executable demo project like these and share it on your GitHub repository.

Thank you!

[HuaJFrame]

Hello @harawata ,
I created a demo project to reproduce the issue mentioned above.

I think the issue occurs in the MapperMethod and MapperAnnotationBuilder classes.

For example, in MapperMethod line 294:

this.returnsMany = configuration.getObjectFactory().isCollection(this.returnType) || this.returnType.isArray();

When the return type is byte[], this causes the program to treat the returned result as a collection or array.

If possible, I would like to try to fix this issue and add test cases, then submit a PR later.

[HuaJFrame]

I would like to try changing it like this:

this.returnsMany = (configuration.getObjectFactory().isCollection(this.returnType) || this.returnType.isArray())
          && !configuration.getTypeHandlerRegistry().hasTypeHandler(this.returnType);

Although the return type is an array, if it is registered in the TypeHandlerRegistry , it should not be treated as a collection or array result.

ByteArrayTypeHandler is registered in the TypeHandlerRegistry, so when the return type is byte[], the result of this check is false.

[harawata]

Hi @xufeng888 @HuaJFrame ,

This is a known limitation and, as you found out, using Object as the return type is the simplest workaround.

Unfortunately, a simple fix like #3698 breaks backward compatibility.

I thought about addressing this issue in 3.6.x, but decided not to because 1) there is an OK-ish workaround (i.e. using Object) and 2) there had been few interests.
I will revisit my idea when I have some time.