PoiUtils initRowField add thread security

easyexcel-core/src/main/java/com/alibaba/excel/util/PoiUtils.java

@@ -1,6 +1,9 @@
 package com.alibaba.excel.util;
 
+import java.lang.reflect.Field;
+
 import com.alibaba.excel.exception.ExcelRuntimeException;
+
 import org.apache.poi.hssf.record.RowRecord;
 import org.apache.poi.hssf.usermodel.HSSFRow;
 import org.apache.poi.ss.usermodel.Row;
@@ -8,8 +11,6 @@ import org.apache.poi.util.BitField;
 import org.apache.poi.util.BitFieldFactory;
 import org.apache.poi.xssf.usermodel.XSSFRow;
 
-import java.lang.reflect.Field;
-
 /**
  * utils
  *
@@ -22,7 +23,7 @@ public class PoiUtils {
      */
     public static final BitField CUSTOM_HEIGHT = BitFieldFactory.getInstance(0x640);
 
-    private static Field ROW_RECORD_FIELD;
+    private static volatile Field ROW_RECORD_FIELD;
 
     /**
      * Whether to customize the height
@@ -32,16 +33,20 @@ public class PoiUtils {
      */
     public static boolean customHeight(Row row) {
         if (row instanceof XSSFRow) {
-            XSSFRow xssfRow = (XSSFRow) row;
+            XSSFRow xssfRow = (XSSFRow)row;
             return xssfRow.getCTRow().getCustomHeight();
         }
         if (row instanceof HSSFRow) {
-            HSSFRow hssfRow = (HSSFRow) row;
+            HSSFRow hssfRow = (HSSFRow)row;
             try {
+                if (ROW_RECORD_FIELD == null) {
+                    synchronized (PoiUtils.class) {
                         if (ROW_RECORD_FIELD == null) {
                             initRowRecordField();
                         }
-                RowRecord record = (RowRecord) ROW_RECORD_FIELD.get(hssfRow);
+                    }
+                }
+                RowRecord record = (RowRecord)ROW_RECORD_FIELD.get(hssfRow);
                 return CUSTOM_HEIGHT.getValue(record.getOptionFlags()) == 1;
             } catch (IllegalAccessException ignore) {
             }
@@ -49,7 +54,6 @@ public class PoiUtils {
         return false;
     }
 
-
     private static void initRowRecordField() {
         try {
             ROW_RECORD_FIELD = HSSFRow.class.getDeclaredField("row");