2.7 插入超大的字符串文本内容
MyBatis框架也支持Oracle的CLOB,不需要特别的环境配置即可完成对CLOB字段的操作。
创建名为bigCLOB的Web项目,映射文件userinfoMapping.xml的代码如下。
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "mybatis-3-mapper.dtd">
<mapper namespace="mybatis.testcurd">
<insert id="insertBigString" parameterType="map">
<selectKey keyProperty="id" order="BEFORE" resultType="java.lang.Long">
select idauto.nextval from dual
</selectKey>
insert into bigclob(id,bigstring) values(#{id},#{bigstring})
</insert>
<select id="selectById" resultType="map">
select * from bigclob where
id=10000
</select>
</mapper>```
创建名为test的Servlet,核心代码如下。
public class test extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
try {
SqlSession sqlSessionRef = GetSqlSession.getSqlSession();
Map map = sqlSessionRef.selectOne("selectById");
Clob clobRef = (Clob) map.get("BIGSTRING");
Reader reader = clobRef.getCharacterStream();
BufferedReader brRef = new BufferedReader(reader);
char[] charArray = new char[2048];
int readLength = brRef.read(charArray);
while (readLength != -1) {
String bigString = new String(charArray, 0, readLength);
System.out.println(bigString);
readLength = brRef.read(charArray);
}
Map insertMap = new HashMap();
insertMap.put("id", 20000);
insertMap.put("bigstring", clobRef);
sqlSessionRef.insert("insertBigString", insertMap);
sqlSessionRef.commit();
sqlSessionRef.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}`
默认情况下Oracle数据表中有一条包含50万行的CLOB字段,如图2-11所示。
程序运行后,在控制台输出了最后一行信息,如图2-12所示。
数据表中还插入了另外一条50万行的记录,如图2-13所示。
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