java操作clob字段

 

java操作clob字段
在oracle数据库中如何插入CLOB值 oracle中最常用的varcher2类型最多只能存储4000个字节的内容，一般情况下是能够满足用户的需求的。但是在一些特殊情况下（如要存储图片或者要存储的内容超过了4000个字节），varcher2就满足不了这个需求了。这个时候我们可以借助于oracle里面的大字段CLOB,后者 BLOB。举例如下： 首先，在数据库中建一张表news，为了简单起见，只有一个字段content（CLOB）。做好准备工作后就可以开始我们的CLOB之旅了。 以下是插入CLOB的代码：

import java.sql.*;

import java.io.*;

public class TestClob{

public void TestClob(){}

public static void main(String args[]){

try{

     Class.forName("oracle.jdbc.driver.OracleDriver");

Connectionconn=DriverManager.getConnection ("jdbc:oracle:thin:@localhost:1521:ora32","tjpt","tjpt");     conn.setAutoCommit(false); //第一步：插入一个空的CLOB

String sql1="insert into news(content,id) values (EMPTY_CLOB(),'1')";

PreparedStatement ps1=conn.prepareStatement(sql1);

ps1.executeUpdate(); ps1.close(); //第二步：取出该CLOB

String sql2="select content from news for update";

PreparedStatement ps2=conn.prepareStatement(sql2);

ResultSet rs2=ps2.executeQuery();

while (rs2.next()){

oracle.sql.CLOB clob=(oracle.sql.CLOB)rs2.getClob(1);

BufferedWriter out=new BufferedWriter(clob.getCharacterOutputStream());

String content="1234";//假定这是新闻的内容，当然可以也可以是其他的内容

out.write(content,0,content.length());

out.close();

}

conn.commit();

} catch(Exception e){e.printStackTrace();}

}

}

既然插入进去了，那我们还得要检验一下：插进去的是不是你想插进去的内容？以下就是读取CLOB的代码： import java.sql.*;

import java.io.*;

public class ReadClob{

public void ReadClob(){}

public static void main(String args[]){

try{

Class.forName("oracle.jdbc.driver.OracleDriver");

Connection conn=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:ora32","tjpt","tjpt"); String sql1="select content from news";

PreparedStatement ps1=conn.prepareStatement(sql1);

ResultSet rs1=ps1.executeQuery();

while (rs1.next()){

oracle.sql.CLOB clob=(oracle.sql.CLOB)rs1.getClob(1);

BufferedReader in=new BufferedReader(clob.getCharacterStream());

StringWriter out=new StringWriter();

int c;

while((c=in.read())!=-1){

out.write(c);

}

String content=out.toString();

System.out.println (content);//输出CLOB内容 }

} catch(Exception e){e.printStackTrace();

}

}

}



例题2：插入

//ReportEntity 存放数据的bean

public boolean AddMonth_Report(ReportEntity re) throws Exception {
Connection conn = null;
Statement st = null;
ResultSet rs = null;

////这个sql是先插入空值,占个位子

               String sql =
"insert into staff_monthform(id,memb_id,m_plan,m_summery,m_date) values"
+ " (SEQ_MID.nextval,'" +   re.getMEMB_ID()+
"',empty_clob(),empty_clob(),sysdate)";

//clob型的字段要先以empty_clob()空值插入;然后用update把数据修改进去
try {
conn = ConnectionPool.getConnection();//连接池
conn.setAutoCommit(false);
st = conn.createStatement();
st.executeUpdate(sql);

//这个sql执行的是update,先将该条记录锁定,再修改数据
String sql2 = "select m_plan from staff_monthform where memb_id='" +
re.getMEMB_ID() + "' "
+
" and   to_char(M_DATE,'mm')=to_char(sysdate,'mm') for update";
rs = st.executeQuery(sql2);
oracle.sql.CLOB clobtt = null;
if (rs.next()) {
try {
oracle.sql.CLOB clob = (oracle.sql.CLOB) rs.getObject(1); //clob
Writer outstream = clob.getCharacterOutputStream(); //字符 输出流
outstream.write(new String(re.getM_PLAN().getBytes(
"ISO8859_1"))); //写
outstream.close();

                       } catch (Exception ex) {
ex.printStackTrace();
}

                       return true;
}
conn.commit();

               } catch (Exception ex) {
ex.printStackTrace();
} finally {
try {

                       if (rs != null) {
rs.close();
}
if (st != null) {
st.close();
}
if (conn != null) {
ConnectionPool.close(conn);
}
} catch (Exception sqlex) {
Logger.error(sqlex.getMessage());
}

               }
return false;
}



在s2sh操作clob字段时，更新的时候容易出现这种错误：

不允许的操作: streams type cannot be used in batching


解决方法如下：

近日程序的数据库转为oracle 在操作blob类型时报以下错误：不允许的操作: streams type cannot be used in batching。经过查找多方面的资料查证Oracle JDBC不允许流操作以批量方式执行(Oracle CLOB采用流机制作为数据读写方式)。 只需在spring配置文件中更改hibernate jdbc.batch_size为0即可。

<bean id="oracleSessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
        <property name="dataSource">
            <ref bean="oracleDataSource"/>
        </property>
        <property name="hibernateProperties">
            <props>
                <prop key="hibernate.dialect">org.hibernate.dialect.Oracle9Dialect</prop>
                <prop key="connection.provider_class">
                    org.hibernate.connection.C3P0ConnectionProvider
                </prop>
                <prop key="hibernate.show_sql">true</prop>
                <prop key="hibernate.cache.use_query_cache">true</prop>
                <prop key="hibernate.cache.provider_class">
                    org.hibernate.cache.EhCacheProvider
                </prop>
                <prop key="hibernate.jdbc.batch_size">0</prop>
            </props>
        </property>
<bean id="oracleSessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> <property name="dataSource"> <ref bean="oracleDataSource"/> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">org.hibernate.dialect.Oracle9Dialect</prop> <prop key="connection.provider_class"> org.hibernate.connection.C3P0ConnectionProvider </prop> <prop key="hibernate.show_sql">true</prop> <prop key="hibernate.cache.use_query_cache">true</prop> <prop key="hibernate.cache.provider_class"> org.hibernate.cache.EhCacheProvider </prop> <prop key="hibernate.jdbc.batch_size">0</prop> </props> </property>