设有表：create table blobimg (id int primary key, contents blob);一、BLOB入库的专用访问： 1) 最常见于Oracle的JDBC示例中 一般是先通过select ... for update锁定blob列，然后写入blob值，然后提交。要用到特定的Oracle BLOB类。 Class.forName("oracle.jdbc.driver.OracleDriver"); Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:testdb", "test", "test"); //处理事务 con.setAutoCommit(false); Statement st = con.createStatement(); //插入一个空对象 st.executeUpdate("insert into BLOBIMG values(1,empty_blob())"); //用for update方式锁定数据行 ResultSet rs = st.executeQuery( "select contents from BLOBIMG where id=1 for update"); if (rs.next()) { //使用oracle.sql.BLOB类，没办法了，变成专用的了 oracle.sql.BLOB blob = (oracle.sql.BLOB) rs.getBlob(1).; //到数据库的输出流 OutputStream outStream = blob.getBinaryOutputStream(); //这里用一个文件模拟输入流 File file = new File("d://proxy.txt"); InputStream fin = new FileInputStream(file); //将输入流写到输出流 byte[] b = new byte[blob.getBufferSize()]; int len = 0; while ( (len = fin.read(b)) != -1) { outStream.write(b, 0, len); } //依次关闭 fin.close(); outStream.flush(); outStream.close(); } con.commit(); con.close(); 2) 再厉害一点的，是通过调用DBMS_LOB包中的一些函数来处理，效率好像也不错. 不过，要使用到存储过程，用到专用类OracleCallableStatement。 例： import java.sql.*; import java.io.*; import oracle.jdbc.driver.*; import oracle.sql.*; class TestBlobWriteByDBMS_LOB { public static void main (String args []) throws SQLException , FileNotFoundException, IOException { DriverManager.registerDriver (new oracle.jdbc.driver.OracleDriver()); Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:ora92","scott","tiger"); conn.setAutoCommit(false); Statement stmt = conn.createStatement(); stmt.execute( "delete from demo" ); System.out.println( "deleted from demo" ); stmt.execute( "insert into demo (id,theBlob) values (s_enr.nextval,empty_blob())" ); conn.commit(); System.out.println( "committed" ); ResultSet rset = stmt.executeQuery ("SELECT theBlob FROM demo where id = s_enr.currval FOR UPDATE"); System.out.println( "Executed Query" ); if(rset.next()) { System.out.println( "Fetched row " ); BLOB l_mapBLOB = ((OracleResultSet)rset).getBLOB(1); File binaryFile = new File("e://free//jo.jpg"); FileInputStream instream=new FileInputStream(binaryFile); int chunk = 32000; System.out.println( "Chunk = "+ chunk ); byte[] l_buffer = new byte[chunk]; int l_nread = 0; OracleCallableStatement cstmt = (OracleCallableStatement)conn.prepareCall( "begin dbms_lob.writeappend( :1, :2, :3 ); end;" ); cstmt.registerOutParameter( 1, OracleTypes.BLOB ); while ((l_nread= instream.read(l_buffer)) != -1) { cstmt.setBLOB( 1, l_mapBLOB ); cstmt.setInt( 2, l_nread ); cstmt.setBytes( 3, l_buffer ); cstmt.executeUpdate(); l_mapBLOB = cstmt.getBLOB(1); } instream.close(); conn.commit(); rset.close(); stmt.close(); conn.close(); } } } 二、BLOB值读取的通用处理：这个jdbc标准接口可以直接调用，因此比较简单，如下所示： Connection con = ConnectionFactory.getConnection(); con.setAutoCommit(false); Statement st = con.createStatement(); ResultSet rs = st.executeQuery("select contents from BLOBIMG where id=1"); if (rs.next()) { java.sql.Blob blob = rs.getBlob(1); InputStream ins = blob.getBinaryStream(); //输出到文件 File file = new File("d://output.txt"); OutputStream fout = new FileOutputStream(file); //下面将BLOB数据写入文件 byte[] b = new byte[1024]; int len = 0; while ( (len = ins.read(b)) != -1) { fout.write(b, 0, len); } //依次关闭 fout.close(); ins.close(); } con.commit(); con.close();三、BLOB值写入的通用处理： 这时要借助于PreparedStatement的动态绑定功能，借用其setObject()方法插入字节流到BLOB字段。 public void insertFile(File f) throws Exception{ FileInputStream fis=new FileInputStream(f,Connection conn); byte[] buffer=new byte[1024]; data=null; int sept=0;int len=0; while((sept=fis.read(buffer))!=-1){ if(data==null){ len=sept; data=buffer; }else{ byte[] temp; int tempLength; tempLength=len+sept; temp=new byte[tempLength]; System.arraycopy(data,0,temp,0,len); System.arraycopy(buffer,0,temp,len,sept); data=temp; len=tempLength; } if(len!=data.length()){ byte temp=new byte[len]; System.arraycopy(data,0,temp,0,len); data=temp; } } String sql="insert into fileData (filename,blobData) value(?,?)"; PreparedStatement ps=conn.prepareStatement(sql); ps.setString(1,f.getName()); ps.setObject(2,data); ps.executeUpdate(); }
四. CLOB读取的通用处理 public static String getClobString(ResultSet rs, int col) { try { Clob c=resultSet.getClob(2); Reader reader=c.getCharacterStream(): if (reader == null) { return null; } StringBuffer sb = new StringBuffer(); char[] charbuf = new char[4096]; for (int i = reader.read(charbuf); i > 0; i = reader.read(charbuf)) { sb.append(charbuf, 0, i); } return sb.toString(); } catch (Exception e) { return ""; } }当然还可以直接编写BLOB存取的存储过程供JDBC调用，那也非常方便。不过可能要用到外部LOB类型。这将在后边陆续进行介绍。
