JDBC操作ORACLE的CLOB型字段

昨天在项目中有一个操作数据库的方法抛出一个异常"仅可以为插入 LONG 列的 LONG 值赋值"

上网搜说是数据库字段定义为VARCHAR2()时,如果插入字符界于1000~2000的时候就会发生这个异常,处理方式总结有如下几个:

1.将数据拆分成多个字段来存储.

 

2.换一个oracle驱动(如将classes12.jar换成ojdbc14.jar),试过了好像没用

 

3.将字段类型改为CLOB

 

没办法,只好选择第三种,上网查了些操作CLOB对象的资料,如下:

建表sql:

-- Create table T_CLOBTEST
CREATE TABLE T_CLOBTEST
(
 ID VARCHAR2(20),
 CLOBCOLUMN CLOB
);

-- Add comments to the columns
comment on column T_CLOBTEST.ID is '流水号';
comment on column T_CLOBTEST.CLOBCOLUMN is 'Clob字段';

----------------------------------------------------------------------------------------------------------------------------------

 

数据库表的对象:

 

public class ClobEntity {

 private String id = "";
 
 private String clobColumn = "";

 public String getClobColumn() {
  return clobColumn;
 }

 public void setClobColumn(String clobColumn) {
  this.clobColumn = clobColumn;
 }

 public String getId() {
  return id;
 }

 public void setId(String id) {
  this.id = id;
 }
}

---------------------------------------------------------------------------------------------------------------------------------

 

 

数据库操作类代码:

 

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import oracle.sql.CLOB;

import com.baosight.demo.entity.ClobEntity;
import com.baosight.demo.util.DBUtil;

public class ClobTestDAO {

 /**
  * @param args
  */
 public static void main(String[] args) {

  /*ClobEntity clobEntity = new ClobEntity();
  clobEntity.setId("1");
  new ClobTestDAO().insert(clobEntity);*/
  new ClobTestDAO().queryById("1", "f:/fjdaljf.java");
 }

 /**
  * 新增记录
  * @param ClobEntity
  */
 public void insert(ClobEntity clobEntity) {

     try {
      //获取数据库操作句柄
      Connection conn = new DBUtil().getConn();
      //设为不自动提交
      conn.setAutoCommit(false);
      Statement stmt = conn.createStatement();

      //先初始化CLOB字段,此处为必须的操作,否则后面会产生空指针异常
      String initSql = "INSERT INTO T_CLOBTEST VALUES('" + clobEntity.getId() + "', EMPTY_CLOB())";
      //读取CLOB字段
      String updateSql = "SELECT CLOBCOLUMN FROM T_CLOBTEST WHERE ID = '" + clobEntity.getId() + "'";
      stmt.executeUpdate(initSql);
      ResultSet rs = stmt.executeQuery(updateSql);
   if (rs.next()) {
       CLOB clob = (CLOB) rs.getClob(1); //获取CLOB字段内容并转换为 oracle.sql.CLOB类型
       //获取CLOB的输出流
       Writer os = clob.getCharacterOutputStream();
      
       String insertValue = clobEntity.getClobColumn();
      
       os.write(insertValue);
       os.flush();
       os.close();
       conn.commit();
          conn.close();
   }
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (SQLException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }
 
 /**
  * 根据ID读取(CLOB)数据,生成到指定硬盘目录下
  * @param String
  */
 public void queryById(String id, String filePath) {

     try {
      Connection conn = new DBUtil().getConn();
      conn.setAutoCommit(false);
      Statement st = conn.createStatement();
      PreparedStatement preparedStatement = conn.prepareStatement("SELECT CLOBCOLUMN FROM T_CLOBTEST WHERE ID = '" + id + "'");
      ResultSet rs = preparedStatement.executeQuery();
      if (rs.next()) {
          //获取CLOB字段信息
          CLOB clob = (CLOB)rs.getClob("CLOBCOLUMN");
          BufferedReader br = new BufferedReader(clob.getCharacterStream());
          //创建输出流
          BufferedWriter out = new BufferedWriter(new FileWriter(filePath));
          String line = br.readLine();
          while (line != null) {
           //往目录文件中写出数据
              out.write(line);
              System.out.println(line);
              line = br.readLine();
              out.flush();
          }
          out.close();
          br.close();
      }
      rs.close();
      st.close();
      conn.close();

  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (SQLException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }
 }
}

 

 

用到的包:classes12.jar