Oracle中Blob字段的写入处理(一)

** Oracle ** ** 中 ** ** Blob ** ** 字段的写入处理(一) ** ** **

韦 伟

Oracle 中的 Bloc 字段的处理较其他字段来说,会有一些特殊性。现就对在 java 和 pl/sql 下, Blob 字段的处理和大家做一些交流。

下面,简单介绍一下 Blob 在以下两种环境中的写入处理,

u java 环境

u PL/SQL 环境

一、 java 环境

1、 Blob 的插入操作

  1. 插入一空的 Blob 。

  2. 更新该纪录的 Blob 。

例子:

比如表结构如下:

CREATE TABLE Student (

Name VARCHAR2(30),

Age Int,

Picture Blob);

i. 插入一空的 Blob 。

String command=”INSERT INTO Student VALUES(?,?,?)”;

Connection conn=null;

PreparedStatement ps=null;

try

{

conn=….;

ps=conn. prepareStatement(command);

ps.setString(1,”ZhangSan”);

ps.setInt(2,20);

ps.setBlob(3, BLOB.empty_lob());

ps.executeUpdate();

ii. 更新该纪录

byte[] data=null;

Connection conn=null;

Try

{

data=… // 图片信息

conn=..

ByteArrayInputStream in=new ByteArrayInputStream(data);

updateBlob(in, conn, “ Student”,”Picture”,”Name”,”zhangsan”);

public static void updateBlob( InputStream instream,

Connection conn,

String table,

String blobColumn,

String keyColumn,

String keyValue)

throws SQLException, IOException

{

Statement stmt = null;

OracleResultSet rs = null;

BLOB blob = null;

boolean oldAutoCommit = conn.getAutoCommit();

StringBuffer sqlBuffer = new StringBuffer();

try {

conn.setAutoCommit(false);

sqlBuffer.append("select ");

sqlBuffer.append(blobColumn);

sqlBuffer.append(" from ");

sqlBuffer.append(table);

sqlBuffer.append(" where ");

sqlBuffer.append(keyColumn);

sqlBuffer.append("='");

sqlBuffer.append(keyValue);

// 注意这里的 ”for update”

sqlBuffer.append("' for update ");

stmt = conn.createStatement();

rs = (OracleResultSet) stmt.executeQuery(sqlBuffer.toString());

if (!rs.next())

{

rs.close();

stmt.close();

throw new IllegalArgumentException(

"no record found for keyValue: '" + keyValue + "'");

}

blob = rs.getBLOB(1);

OutputStream outstream = blob.getBinaryOutputStream();

int bufferSize = blob.getChunkSize();

byte[] buffer = new byte[bufferSize];

int bytesRead = -1;

while ((bytesRead = instream.read(buffer)) != -1)

{

outstream.write(buffer, 0, bytesRead);

}

instream.close();

outstream.close();

rs.close();

stmt.close();

}

catch (SQLException e)

{

throw e;

}

catch (IOException e)

{

throw e;

}

finally {

conn.setAutoCommit(oldAutoCommit);

}

}

二、 PL/SQL 下

( 例子表结构如一所示 )

i. 插入一空的 Blob 。

declare

bufferBlob BLOB;

data RAW(…)

INSERT INTO Student VALUES(‘zhangsan’, 20 , empty_blob() );

ii. 更新该纪录的 Blob 。

SELECT Picture INTO bufferBlob FROM Student WHERE Name=’zhangsan’ FOR UPDATE;

DBMS_LOB.OPEN(bufferBlob , dbms_lob.lob_readwrite );

dbms_lob.write (bufferBlob , utl_raw.length( data) , data);

( 待续 )

Published At
Categories with 数据库类
Tagged with
comments powered by Disqus