如何从java中的xml中提取某些块？

I have the following xml file.

我有以下xml文件。

<?xml version="1.0" encoding="UTF-8"?>
<databaseChangeLog>
   <changeSet author="debdipta.h (generated)" id="1442927616936-399">
      <createTable tableName="SI_FORWARDING_EVENT_HISTORY_AU">
         <column name="FORWARDING_ID_O" type="NUMBER" />
         <column name="FORWARDING_ID_N" type="NUMBER" />
         <column name="ASSIGNMENT_ID_O" type="NUMBER" />
         <column name="ASSIGNMENT_ID_N" type="NUMBER" />
         <column name="PROCESS_INSTANCE_ID_O" type="NUMBER" />
         <column name="PROCESS_INSTANCE_ID_N" type="NUMBER" />
         <column name="ORIGINAL_USER_ID_O" type="NUMBER" />
         <column name="ORIGINAL_USER_ID_N" type="NUMBER" />
         <column name="FORWARD_FROM_USER_O" type="NUMBER" />
         <column name="FORWARD_FROM_USER_N" type="NUMBER" />
         <column name="FORWARD_TO_USER_O" type="NUMBER" />
         <column name="FORWARD_TO_USER_N" type="NUMBER" />
         <column name="COMMENTS_O" type="VARCHAR2(4000 CHAR)" />
         <column name="COMMENTS_N" type="VARCHAR2(4000 CHAR)" />
         <column name="XML_O" type="VARCHAR2(4000 CHAR)" />
         <column name="XML_N" type="VARCHAR2(4000 CHAR)" />
         <column name="CREATED_BY_O" type="NUMBER" />
         <column name="CREATED_BY_N" type="NUMBER" />
         <column name="CREATION_DATE_O" type="date" />
         <column name="CREATION_DATE_N" type="date" />
         <column name="AUDIT_TRAIL_REASON" type="VARCHAR2(1000 CHAR)" />
         <column name="TRANSACTION_TYPE" type="VARCHAR2(100 CHAR)" />
      </createTable>
   </changeSet>

   <changeSet author="deb.h" id="4588999797">
      <createView />
   </changeSet>

   <changeSet author="deb.h" id="4588999797">
      <createTable />
   </changeSet>

   <changeSet author="deb.h" id="4588999797">
      <createView />
   </changeSet>
</databaseChangeLog>
<