Mapper method 'com.xxxx.other.dao.MyDao.getNo attempted to return null from a method with a primitive return type (int)

使用myBatis调用存储过程的返回值，提示错误信息:

org.apache.ibatis.binding.BindingException: Mapper method 'com.xxxx.other.dao.MyDao.getNo attempted to return null from a method with a primitive return type (int).

先查mysql监控语句，发现存储过程调用正常，也得到了返回值，继续查

对应的文件

存储过程:

CREATE PROCEDURE `Get_Table_Flow_No`(IN `输入表名` VARCHAR(100), IN `待取数` INT, OUT `输出要取的最大流水号` INT)
BEGIN
	DECLARE `willRetNo` INT;

	SET `输出要取的最大流水号` = 0 ;

	SELECT 字段_已取最大流水号 INTO `willRetNo`  FROM 流水号保存表  WHERE 字段_表名=`输入表名` for UPDATE;  

	IF `willRetNo` IS NULL  THEN
		SET `willRetNo` = `待取数` ;
		INSERT INTO `流水号保存表`
			(字段_表名,字段_已取最大流水号,字段_上次获取时间)
		VALUES (`输入表名`, `willRetNo`, NOW());
	ELSE
		SET `willRetNo` = `willRetNo` + `待取数` ;

		UPDATE `流水号保存表`
        SET 字段_已取最大流水号 = `willRetNo` 
			, 字段_上次获取时间 = NOW()
		WHERE 字段_表名=`输入表名` ;
	END IF;  
        
    SET `输出要取的最大流水号` = `willRetNo`;
 
END

　　MyDao.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.xxxx.other.dao.MyDao">
    <parameterMap type="java.util.Map" id = "FlowNoMap">
        <parameter property="输入表名" mode="IN" jdbcType="VARCHAR"/>
        <parameter property="待取数" mode="IN" jdbcType="INTEGER"/>
        <parameter property="返回最大数值" mode="OUT" jdbcType="INTEGER"/>
    </parameterMap>

    <select id="getFlowNo" parameterMap="FlowNoMap" statementType="CALLABLE">
        <if test="_databaseId == 'mysql'">
             call Get_Table_Flow_No(#{输入表名 ,jdbcType=VARCHAR,mode=IN},#{待取数,jdbcType=INTEGER,mode=IN},#{返回最大数值 ,jdbcType=INTEGER,mode=OUT});
        </if>
        <if test="_databaseId == 'sqlserver'"></if>
    </select>

</mapper>

　　MyDao.java

package com.xxxx.other.dao;

import org.apache.ibatis.annotations.Param;
import org.springframework.dao.DataAccessException;

import java.util.List;
import java.util.Map;

public interface MyDao {
    int getNo(Map<String, Object> parameterMap) throws DataAccessException;
}

错误信息出在:

org/apache/ibatis/binding/MapperMethod.java 方法 execute 中

    if (result == null && method.getReturnType().isPrimitive() && !method.returnsVoid()) {
      throw new BindingException("Mapper method '" + command.getName() 
          + " attempted to return null from a method with a primitive return type (" + method.getReturnType() + ").");
    }

　　因为result 为 null,所以抛出了异常,往上推,同文件中

else if (SqlCommandType.SELECT == command.getType()) {
      if (method.returnsVoid() && method.hasResultHandler()) {
        executeWithResultHandler(sqlSession, args);
        result = null;
      } else if (method.returnsMany()) {
        result = executeForMany(sqlSession, args);
      } else if (method.returnsMap()) {
        result = executeForMap(sqlSession, args);
      } else {
        Object param = method.convertArgsToSqlCommandParam(args);
        result = sqlSession.selectOne(command.getName(), param);
      }
    }

　调用的是最后一个条件:

Object param = method.convertArgsToSqlCommandParam(args);
result = sqlSession.selectOne(command.getName(), param);
调用的存储过程中，只是把值通过输出参数返回出来，没提供select语句，所以result为空,但param中有对"返回最大数值"取到值
再返回报错的地方,看到有验证条件: !method.returnsVoid() ,实际在myDao.xml中是没有返回的，查询 MyDao.java,
接口中有返回值: int getNo(Map<String, Object> parameterMap) throws DataAccessException;
把 int 调整为 void, 程序运行正常,通过 parameterMap 取到了最大数