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Oracle中大文本操作实例



作者:    文章来源:
发布日期:2007年02月06日
一直用Oracle,都为大文本段插入而困惑,
以前都是用文件来保存大文本。^_^

今天终于静下心来,解决这个问题
没有经过很多的测试,所以想贴出来,给大家测一测
也因为,在网上很难找到这样的资料(最少我找了很久,但是能用的很少),
所以,也可以当作一块引路石。
如果大家还有什么好的方法,来讨论一下吧 ^_^

import java.sql.*;
import java.io.*;
import java.util.*;
import oracle.sql.BLOB;
import oracle.sql.*;
import oracle.jdbc.driver.*;

/**
* LOB Operation Util.
* @author Peng Chen[Pizer.Chen -- ICEANT]
* @author iceant@21cn.com
* @version 1.0
*/
public class LOBUtil {
public LOBUtil(){}

/**
* String2LOB store String to LOB
* @param data String need to be stored.
* @param table_name Table name
* @param lob_field_name LOB Field
* @param key_field Primary Key Field
* @param key_value Primary Key value
*/
public boolean String2LOB(Connection conn,
String data,
String table_name,
String lob_field_name,
String key_field,
String key_value)throws SQLException{
try {

BLOB lob = getBLOB(conn,table_name,lob_field_name,key_field,key_value);

OutputStream os = lob.getBinaryOutputStream();
java.io.BufferedOutputStream bos = new java.io.BufferedOutputStream(os);
bos.write(data.getBytes());//Stored String data to BLOB field
bos.flush();
bos.close();
os.close();
return true;
} catch(SQLException sqle){
throw sqle;
}catch (Exception err) {
//err.printStackTrace();
return false;
}
}

private static void log(String msg){
System.out.println(msg);
}

private BLOB getBLOB(Connection conn,
String table_name,
String lob_field_name,
String key_field,
String key_value)throws SQLException{
BLOB lob = null;
try {
StringBuffer sql = new StringBuffer(1024);
sql.append("select ").append(lob_field_name).append(" from ");
sql.append(table_name).append(" where ").append(key_field);
sql.append(" =? for UPDATE ");
//sql.append(" = `").append(key_value).append("` for update");
//System.out.println(sql.toString());
// Prepared to get LOB field
PreparedStatement pstmt = conn.prepareStatement(sql.toString());
pstmt.setString(1,key_value);
//Statement pstmt = conn.createStatement();
//ResultSet rs = pstmt.executeQuery(sql.toString());

// == BUG ==
//SYSTEM maybe halt here when sqlplus is running and sth is not commited.

ResultSet rs = pstmt.executeQuery();
if (rs.next()) {
lob = ((OracleResultSet)rs).getBLOB(1);
pstmt.close();
return lob;
} else {
pstmt.close();
throw new SQLException("LOB field can not be found. Please check it again.");
}
} catch (Exception err) {
try{
conn.rollback();
}catch(SQLException sqle){
}
throw new SQLException(err.getMessage());
}
}

/**
* LOB2String get String data from LOB
* @param conn @see java.sql.Connection Object
* @param table_name Table name
* @param lob_field_name LOB Field
* @param key_field Primary Key Field
* @param key_value Primary Key value
*/
public String LOB2String(
Connection conn,
String table_name,
String lob_field_name,
String key_field,
String key_value) {
try {
BLOB p_BLOB = getBLOB(conn,table_name,lob_field_name,key_field,key_value);
// Open a stream to read BLOB data
InputStream stream = p_BLOB.getBinaryStream();

// Keep BLOB Datas
java.io.ByteArrayOutputStream bos = new java.io.ByteArrayOutputStream();
java.io.OutputStream os = new java.io.BufferedOutputStream(bos);

// Read from the BLOB stream and write to the stringbuffer
int nchars = 0; // Number of chanracters read
byte[] l_buffer = new byte[1024]; // Buffer holding characters being transferred
while ((nchars = stream.read(l_buffer)) != -1) // Read from BLOB
os.write(l_buffer,0,nchars);
os.flush();
os.close();
String result = new String(bos.toByteArray());
stream.close(); // Close the BLOB input stream
bos.close();
return result;
} catch (Exception ex) { // Trap SQL and IO errors
try{
conn.rollback();
}catch(SQLException sqle){
}
return null;
}
}
}

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