!166 selectOne 多条记录抛出异常

Merge pull request !166 from 青苗/3.0

mybatis-plus-core/src/main/java/com/baomidou/mybatisplus/core/mapper/BaseMapper.java

@@ -19,6 +19,7 @@ import com.baomidou.mybatisplus.core.conditions.Wrapper;
 import com.baomidou.mybatisplus.core.metadata.IPage;
 import com.baomidou.mybatisplus.core.toolkit.CollectionUtils;
 import com.baomidou.mybatisplus.core.toolkit.Constants;
+import com.baomidou.mybatisplus.core.toolkit.ExceptionUtils;
 import org.apache.ibatis.annotations.Param;
 
 import java.io.Serializable;
@@ -163,7 +164,9 @@ public interface BaseMapper<T> extends Mapper<T> {
     default T selectOne(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper) {
         List<T> ts = this.selectList(queryWrapper);
         if (CollectionUtils.isNotEmpty(ts)) {
-            System.err.println("One record is expected, but the query result is multiple records");
+            if (ts.size() > 1) {
+                throw ExceptionUtils.mpe("One record is expected, but the query result is multiple records");
+            }
             return ts.get(0);
         }
         return null;