java操作Oracle大数据类型BLOB的存取

条件准备

Oracle数据库中有表如下

CREATE TABLE BOOK(

ID NUMBER PRIMARY KEY,

F BLOB

);

ConnectionManager类不解释。

package org.db;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.InputStream;

import java.io.OutputStream;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

/**

* 此类掩饰java操作Oracle BLOB类型

* @author wanghao

*

*/

public class SaveFile {

private final static String PSQL = "insert into BOOK(ID,F) " + "values(?,EMPTY_BLOB())";

private final static String SSQL = "select F from BOOK where ID = ? for update";

private final static String USQL = "update BOOK set F = ? where ID = ?";

/**

* 将文件存入数据库

* @param file 要存入数据库的文件

* @param id 为了掩饰方便，手动输入 ID

* @throws Exception

*/

public void save(File file,int id) throws Exception {

Connection conn = ConnectionManager.getConnection();

conn.setAutoCommit(false);

PreparedStatement pstmt = null;

PreparedStatement pstmt2 = null;

try {

pstmt = conn.prepareStatement(PSQL);

pstmt2 = conn.prepareStatement(USQL);

pstmt.setInt(1, id);

try {

pstmt.executeUpdate();// 在数据库中插入空对象

} catch (SQLException ex) {

ex.printStackTrace();

}

pstmt = conn.prepareStatement(SSQL);

pstmt.setInt(1, id);

ResultSet rs = pstmt.executeQuery();// 查询新插入的记录

oracle.sql.BLOB pc = null;

while (rs.next()) {

pc = (oracle.sql.BLOB) rs.getBlob(1);

}

byte[] data = file2Byte(file);

pc.putBytes(1, data);

pstmt2.setBlob(1, pc);

pstmt2.setInt(2, id);

pstmt2.executeUpdate();

conn.commit();

} finally {

try {

pstmt.close();

pstmt2.close();

} catch (Exception EE) {

}

}

}

/**

* 将文件转成byte数组

* @param file 被转成 byte数组的file

* @return

* @throws Exception

*/

public byte[] file2Byte(File file) throws Exception{

FileInputStream fin = new FileInputStream(file);

byte[] b = new byte[(int) file.length()];

fin.read(b);

fin.close();

return b;

}

/**

* 从数据库中将文件写入到本地硬盘

* @param id

* @throws Exception

*/

public void readFile(int id) throws Exception{

byte[] b = new byte[1024];

Connection conn = ConnectionManager.getConnection();

PreparedStatement pstmt = null;

String sql = "select F from BOOK where ID = ?";

pstmt = conn.prepareStatement(sql);

pstmt.setInt(1, id);

ResultSet rs = pstmt.executeQuery();// 查询新插入的记录

oracle.sql.BLOB pc = null;

while (rs.next()) {

pc = (oracle.sql.BLOB) rs.getBlob(1);

}

InputStream in = pc.getBinaryStream();

OutputStream os = new FileOutputStream(new File("T:\\io\\java_temp.pdf"));

int len = 0;

while((len=in.read(b))!=-1){

os.write(b,0,len);

}

os.flush();

os.close();

in.close();

rs.close();

pstmt.close();

conn.close();

}

public static void main(String[] args) throws Exception{

SaveFile sf = new SaveFile();

// File file = new File("T:\\io\\java.pdf");

int id = 2;

// sf.save(file, id);

sf.readFile(id);

}

}