mybatis拼接sql导致的oom报错 GC报错

报错1：mybatis拼接过多

java.lang.OutOfMemoryError: GC overhead limit exceeded

具体报错：

nested exception is org.apache.ibatis.builder.BuilderException:
Error evaluating expression 'ew.sqlSegment != null and ew.sqlSegment != '' and ew.nonEmptyOfWhere'.
Cause: org.apache.ibatis.ognl.OgnlException: 
sqlSegment [java.lang.OutOfMemoryError: GC overhead limit exceeded

一看报错内容，有builder，expression，sqlSegment，ognl，就可以推测出，应该是mybatis拼接条件太多，导致内存超了。例如条件in里，code太多，或者id太多。

oracle官方对 java.lang.OutOfMemoryError: GC overhead limit exceeded 解释如下：

Exception in thread thread_name: 
java.lang.OutOfMemoryError: GC Overhead limit exceeded Cause: 
The detail message "GC overhead limit exceeded" indicates that 
the garbage collector is running all the time 
and Java program is making very slow progress. 
After a garbage collection, 
if the Java process is spending more than approximately 98% of its time doing garbage collection 
and if it is recovering less than 2% of the heap 
and has been doing so far the last 5 (compile time constant) consecutive garbage collections, 
then a java.lang.OutOfMemoryError is thrown. 
This exception is typically thrown 
because the amount of live data barely fits into the Java heap having little free space for new allocations.
 
Action: Increase the heap size. 
The java.lang.OutOfMemoryError exception for GC Overhead limit exceeded can be turned off with the command line flag -XX:-UseGCOverheadLimit.

大致意思是说：

频繁的进行内存回收(最起码已经进行了5次连续的垃圾回收)，JVM就会曝出java.lang.OutOfMemoryError: GC overhead limit exceeded错误。

解决的办法是：

增加堆大小，启动脚本添加参数-Xmx1024m。

或者 关闭GC Overhead limit：-XX:-UseGCOverheadLimit

但由于这是代码本身引起，而非内存不够的问题。所以不建议去改动堆参数或者关闭GC上限。

具体参考

BuilderException OgnlException sqlSegment nonEmptyOfWher OutOfMemoryError:GC overhead limit exceeded_globalcoding的博客-CSDN博客

报错2：

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文章到此已经结束，以下是紫薯补丁

java.lang.OutOfMemoryError: GC overhead limit exceeded

nested exception is org.apache.ibatis.builder.BuilderException:
Error evaluating expression 'ew.sqlSegment != null and ew.sqlSegment != '' and ew.nonEmptyOfWhere'.
Cause: org.apache.ibatis.ognl.OgnlException: 
sqlSegment [java.lang.OutOfMemoryError: GC overhead limit exceeded

Exception in thread thread_name: 
java.lang.OutOfMemoryError: GC Overhead limit exceeded Cause: 
The detail message "GC overhead limit exceeded" indicates that 
the garbage collector is running all the time 
and Java program is making very slow progress. 
After a garbage collection, 
if the Java process is spending more than approximately 98% of its time doing garbage collection 
and if it is recovering less than 2% of the heap 
and has been doing so far the last 5 (compile time constant) consecutive garbage collections, 
then a java.lang.OutOfMemoryError is thrown. 
This exception is typically thrown 
because the amount of live data barely fits into the Java heap having little free space for new allocations.
 
Action: Increase the heap size. 
The java.lang.OutOfMemoryError exception for GC Overhead limit exceeded can be turned off with the command line flag -XX:-UseGCOverheadLimit.