JAVA徹底控制Oracle中BLOB、CLOB說明

//轉自： http://blog.csdn.net/wazj0517/archive/2006/10/19/1341074.aspx

網絡上不少關於JAVA對Oracle中BLOB、CLOB類型字段的操做說明，有的不夠全面，有的不夠準確，甚至有的簡直就是胡說八道。最近的項目正巧用到了這方面的知識，在這裏作個總結。

 

環境：
Database: Oracle 9i
App Server: BEA Weblogic 8.14
表結構：
CREATE TABLE TESTBLOB (ID Int, NAME Varchar2(20), BLOBATTR Blob)
CREATE TABLE TESTBLOB (ID Int, NAME Varchar2(20), CLOBATTR Clob)

 

JAVA能夠經過JDBC，也能夠經過JNDI訪問並操做數據庫，這兩種方式的具體操做存在着一些差別，因爲經過App Server的數據庫鏈接池JNDI得到的數據庫鏈接提供的java.sql.Blob和java.sql.Clob實現類與JDBC方式提供的不一樣，所以在入庫操做的時候須要分別對待；出庫操做沒有這種差別，所以不用單獨對待。

1、BLOB操做
一、入庫
（1）JDBC方式
    //經過JDBC得到數據庫鏈接
    Class.forName("oracle.jdbc.driver.OracleDriver");
    Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:testdb", "test", "test");
    con.setAutoCommit(false);
    Statement st = con.createStatement();
    //插入一個空對象empty_blob()
    st.executeUpdate("insert into TESTBLOB (ID, NAME, BLOBATTR) values (1, "thename", empty_blob())");
    //鎖定數據行進行更新，注意「for update」語句
    ResultSet rs = st.executeQuery("select BLOBATTR from TESTBLOB where ID=1 for update");
    if (rs.next())
    {
        //獲得java.sql.Blob對象後強制轉換爲oracle.sql.BLOB
        oracle.sql.BLOB blob = (oracle.sql.BLOB) rs.getBlob("BLOBATTR");
        OutputStream outStream = blob.getBinaryOutputStream();
        //data是傳入的byte數組，定義：byte[] data
        outStream.write(data, 0, data.length);
    }
    outStream.flush();
    outStream.close();
    con.commit();
    con.close();

（2）JNDI方式
    //經過JNDI得到數據庫鏈接
    Context context = new InitialContext();
    ds = (DataSource) context.lookup("ORA_JNDI");
    Connection con = ds.getConnection();
    con.setAutoCommit(false);
    Statement st = con.createStatement();
    //插入一個空對象empty_blob()
    st.executeUpdate("insert into TESTBLOB (ID, NAME, BLOBATTR) values (1, "thename", empty_blob())");
    //鎖定數據行進行更新，注意「for update」語句
    ResultSet rs = st.executeQuery("select BLOBATTR from TESTBLOB where ID=1 for update");
    if (rs.next())
    {
        //獲得java.sql.Blob對象後強制轉換爲weblogic.jdbc.vendor.oracle.OracleThinBlob（不一樣的App Server對應的可能會不一樣）
        weblogic.jdbc.vendor.oracle.OracleThinBlob blob = (weblogic.jdbc.vendor.oracle.OracleThinBlob) rs.getBlob("BLOBATTR");
        OutputStream outStream = blob.getBinaryOutputStream();
        //data是傳入的byte數組，定義：byte[] data
        outStream.write(data, 0, data.length);
    }
    outStream.flush();
    outStream.close();
    con.commit();
    con.close();

二、出庫
    //得到數據庫鏈接
    Connection con = ConnectionFactory.getConnection();
    con.setAutoCommit(false);
    Statement st = con.createStatement();
    //不須要「for update」
    ResultSet rs = st.executeQuery("select BLOBATTR from TESTBLOB where ID=1");
    if (rs.next())
    {
        java.sql.Blob blob = rs.getBlob("BLOBATTR");
        InputStream inStream = blob.getBinaryStream();
        //data是讀出並須要返回的數據，類型是byte[]
        data = new byte[input.available()];
        inStream.read(data);
        inStream.close();
    }
    inStream.close();
    con.commit();
    con.close();

 

2、CLOB操做
一、入庫
（1）JDBC方式
    //經過JDBC得到數據庫鏈接
    Class.forName("oracle.jdbc.driver.OracleDriver");
    Connection con = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:testdb", "test", "test");
    con.setAutoCommit(false);
    Statement st = con.createStatement();
    //插入一個空對象empty_clob()
    st.executeUpdate("insert into TESTCLOB (ID, NAME, CLOBATTR) values (1, "thename", empty_clob())");
    //鎖定數據行進行更新，注意「for update」語句
    ResultSet rs = st.executeQuery("select CLOBATTR from TESTCLOB where ID=1 for update");
    if (rs.next())
    {
        //獲得java.sql.Clob對象後強制轉換爲oracle.sql.CLOB
        oracle.sql.CLOB clob = (oracle.sql.CLOB) rs.getClob("CLOBATTR");
        Writer outStream = clob.getCharacterOutputStream();
        //data是傳入的字符串，定義：String data
        char[] c = data.toCharArray();
        outStream.write(c, 0, c.length);
    }
    outStream.flush();
    outStream.close();
    con.commit();
    con.close();
（2）JNDI方式
    //經過JNDI得到數據庫鏈接
    Context context = new InitialContext();
    ds = (DataSource) context.lookup("ORA_JNDI");
    Connection con = ds.getConnection();
    con.setAutoCommit(false);
    Statement st = con.createStatement();
    //插入一個空對象empty_clob()
    st.executeUpdate("insert into TESTCLOB (ID, NAME, CLOBATTR) values (1, "thename", empty_clob())");
    //鎖定數據行進行更新，注意「for update」語句
    ResultSet rs = st.executeQuery("select CLOBATTR from TESTCLOB where ID=1 for update");
    if (rs.next())
    {
        //獲得java.sql.Clob對象後強制轉換爲weblogic.jdbc.vendor.oracle.OracleThinClob（不一樣的App Server對應的可能會不一樣）
        weblogic.jdbc.vendor.oracle.OracleThinClob clob = (weblogic.jdbc.vendor.oracle.OracleThinClob) rs.getClob("CLOBATTR");
        Writer outStream = clob.getCharacterOutputStream();
        //data是傳入的字符串，定義：String data
        char[] c = data.toCharArray();
        outStream.write(c, 0, c.length);
    }
    outStream.flush();
    outStream.close();
    con.commit();
    con.close();

二、出庫
    //得到數據庫鏈接
    Connection con = ConnectionFactory.getConnection();
    con.setAutoCommit(false);
    Statement st = con.createStatement();
    //不須要「for update」
    ResultSet rs = st.executeQuery("select CLOBATTR from TESTCLOB where ID=1");
    if (rs.next())
    {
        java.sql.Clob clob = rs.getClob("CLOBATTR");
        Reader inStream = clob.getCharacterStream();
        char[] c = new char[(int) clob.length()];
        inStream.read(c);
        //data是讀出並須要返回的數據，類型是String
        data = new String(c);
        inStream.close();
    }
    inStream.close();
    con.commit();
    con.close();

 

須要注意的地方：
一、java.sql.Blob、oracle.sql.BLOB、weblogic.jdbc.vendor.oracle.OracleThinBlob幾種類型的區別
二、java.sql.Clob、oracle.sql.CLOB、weblogic.jdbc.vendor.oracle.OracleThinClob幾種類型的區別 

公司項目中的用法(博客)：

入庫：先插一個oracle.sql.CLOB.empty_lob()進去，而後

String updateBaseSourceSql = "select content from mb_baseSource where id = ? for update";
    conn.setAutoCommit(false);
    ps = conn.prepareStatement(updateBaseSourceSql);
    ps.setLong(1, result);
    ResultSet rs = ps.executeQuery();
    oracle.sql.CLOB clob = null;
    if (rs.next()) {
     clob = (oracle.sql.CLOB) rs.getClob(1);
    }

    Writer wr = clob.getCharacterOutputStream();
    wr.write(baseSource[4]);
    wr.flush();
    wr.close();
    rs.close();
    ps.close();
    conn.commit();

出庫：

findBaseSourceSql = "select content from mb_baseSource where id = ?";    ps = conn.prepareStatement(findBaseSourceSql);    ps.setLong(1, sourceID);    rs = ps.executeQuery();    if (rs.next()) {     CLOB clob = (oracle.sql.CLOB) rs.getClob(1);     if (clob != null) {      Reader is = clob.getCharacterStream();      BufferedReader br = new BufferedReader(is);      String s = br.readLine();      while (s != null) {       result[6] += s;       s = br.readLine();      }     }    }    rs.close();    ps.close();    conn.close();