weblogic访问ORACLE，thin连接方式存取BLOB和CLOB字段（原创）
weblogic服务器中，在通过datasourse获取connection，BLOB字段取出来的就不是oracle.sql.BLOB类型，而是weblogic封装过的OracleThinBlob类型，执行BLOB oBLOB = (BLOB) rs.getBlob(1);所以cast的时候肯定会出错，出现ClassCaseException异常。一，在使用JDBC直接连接的时候（代码引用dev2dev.bea.com.cn）
详细参见：http://dev2dev.bea.com.cn/bbsdoc/20050971.html#_Toc94603600
java 代码
[*]java.sql.Blob myBlob= null;
[*]
[*]java.sql.Clob myClob= null;
[*]
[*]Connection conn = null;
[*]
[*]Properties props = new Properties();
[*]
[*]props.put("user",user);
[*]
[*]props.put("password", password);
[*]
[*]props.put("server",server);
[*]
[*]Driver myDriver = (Driver)
[*]
[*]Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();
[*]
[*]conn = myDriver.connect("jdbc:oracle:thin:" , props);
[*]
[*]Statement crstmt = conn.createStatement();
[*]
[*]crstmt.execute("create table lobtest (id int, blobcol Blob, clobcol Clob)");//建表
[*]
[*]stmt.execute("insert into lobtest values (44,EMPTY_BLOB(),EMPTY_CLOB())");//插入数据
[*]
[*]stmt.execute("select * from lobtest where id=44");//取数据
[*]
[*]ResultSet rs = stmt.getResultSet();
[*]
[*]while ( rs.next() ) {
[*]
[*]myBlob = rs.getBlob("blobcol");
[*]
[*]}
[*]
[*]
[*]
[*]// Create a byte array and store some data in it
[*]
[*]System.out.println("\nCreating the following byte array:");
[*]
[*]int STREAM_SIZE = 10;
[*]
[*]byte[] b = new byte;
[*]
[*]for (int i=0; i < STREAM_SIZE; i++) {
[*]
[*]b = (byte)(40 + (i%20)); // range 40-60
[*]
[*]System.out.println("byte[" + i + "] = " + b);
[*]
[*]}
[*]
[*]
[*]
[*]// Write the byte array to a stream and store it in the Blob column
[*]
[*]System.out.println
[*]
[*]("\nWriting the byte array to a stream" +
[*]
[*]" and storing it in the table as a blob...");
[*]
[*]InputStream is = new ByteArrayInputStream(b);
[*]
[*]OutputStream os = ((oracle.sql.BLOB) myBlob).getBinaryOutputStream();
[*]
[*]byte[] inBytes = new byte;
[*]
[*]int numBytes = is.read(inBytes);
[*]
[*]
[*]
[*]// write the input stream to the output stream
[*]
[*]while (numBytes > 0) {
[*]
[*]os.write(inBytes, 0, numBytes);
[*]
[*]numBytes = is.read(inBytes);
[*]
[*]}
[*]
[*]// The flush() method causes the data to be written to the table
[*]
[*]os.flush();
[*]
[*]
[*]
[*]//read back the blob
[*]
[*]System.out.println("\nReading the blob back from the table and displaying:");
[*]
[*]Statement readblob = conn.createStatement();
[*]
[*]readblob.execute("select * from lobtest where id=44");
[*]
[*]ResultSet rsreadblob = readblob.getResultSet();
[*]
[*]
[*]
[*]// read the blob into a byte array and display
[*]
[*]byte[] r = new byte;
[*]
[*]while ( rsreadblob.next() ) {
[*]
[*]Blob myReadBlob =rsreadblob.getBlob("blobcol");
[*]
[*]java.io.InputStream readis = myReadBlob.getBinaryStream();
[*]
[*]for (int i=0 ; i < STREAM_SIZE ; i++) {
[*]
[*]r = (byte) readis.read();
[*]
[*]System.out.println("output [" + i + "] = " + r);
[*]
[*]}
[*]
[*]}
[*]
[*]
[*]
[*]
[*]
[*]// create some character data to work with
[*]
[*]String ss = "abcdefghijklmnopqrstuvwxyz";
[*]
[*]System.out.println("\nCreated the following string to be stored as a clob:\n" +
[*]
[*]ss);
[*]
[*]// ============== Manipulating the Clob column ======================
[*]
[*]// get a reference to the clob column
[*]
[*]stmt.execute("select * from lobtest where id=44");
[*]
[*]ResultSet crs = stmt.getResultSet();
[*]
[*]while ( crs.next() ) {
[*]
[*]myClob = crs.getClob("clobcol");
[*]
[*]java.io.OutputStream osss =
[*]
[*]((oracle.sql.CLOB) myClob).getAsciiOutputStream();
[*]
[*]byte[] bss = ss.getBytes("ASCII");
[*]
[*]osss.write(bss);
[*]
[*]osss.flush();
[*]
[*]}
[*]
[*]conn.commit();
[*]
[*]// read back the clob
[*]
[*]System.out.println("\nReading the clob back from the table and displaying:");
[*]
[*]Statement readclob = conn.createStatement();
[*]
[*]readclob.execute("select * from lobtest where id=44");
[*]
[*]ResultSet rsreadclob = readclob.getResultSet();
[*]
[*]// read the clob in as and ASCII stream, write to a character array, and display
[*]
[*]while ( rsreadclob.next() ) {
[*]
[*]Clob myReadClob =rsreadclob.getClob("clobcol");
[*]
[*]java.io.InputStream readClobis = myReadClob.getAsciiStream();
[*]
[*]char[] c = new char;
[*]
[*]for (int i=0 ; i < 26; i++) {
[*]
[*]c = (char) readClobis.read();
[*]
[*]System.out.println("output [" + i + "] = " + c);
[*]
[*]}
[*]
[*]}
[*]
[*]// Drop the table and clean up connections
[*]
[*]System.out.println("\nDropping table...");
[*]
[*]Statement dropstmt = conn.createStatement();
[*]
[*]dropstmt.execute("drop table lobtest");
[*]
[*]System.out.println("Table dropped.");
[*]
[*]} catch (Exception e) {
[*]
[*]System.out.println("Exception was thrown: " + e.getMessage());
[*]
[*]throw e;
[*]
[*]} finally {
[*]
[*]try {
[*]
[*]if (conn != null)
[*]
[*]conn.close();
[*]
[*]} catch (SQLException sqle) {
[*]
[*]System.out.println("SQLException was thrown: " + sqle.getMessage());
[*]
[*]throw sqle;
[*]
[*]}
[*]
[*]}
[*]
[*]}
[*]
二，使用数据源的情况，并且使用oracle thin驱动方式
为了使代码适应各种应用服务器，可以对代码这样修改
[*]在weblogic中找到这个jar包加入到工程项目中。weblogic.jar
[*]在处理BLOB字段的类中添加引用import weblogic.jdbc.vendor.oracle.OracleThinBlob;
[*]取得BLOB字段的时候原来的处理方式是BLOB oBLOB = (BLOB) rs.getBlob(j + 1);这里的BLOB是 oracle.sql.BLOB。在weblogic服务器下这样使用就会报ClassCaseException，因为在强制类型转换的时候，rs.getBlob(j + 1)得到的是OracleThinBlob类型。所以代码更改为
java 代码
[*]if(rs.getBlob(j + 1).getClass().equals(oracle.sql.BLOB.class)) {//except weblogic
[*] BLOB oBLOB = (BLOB) rs.getBlob(j + 1);
[*]
[*]}else{//for weblogic
[*] OracleThinBlob oBLOB = (OracleThinBlob) rs.getBlob(j + 1);
附录：引用自javaeye JAVA完全控制Oracle中BLOB CLOB说明
----------厚厚发表于 2006年06月27日
网络上很多关于JAVA对Oracle中BLOB、CLOB类型字段的操作说明，有的不够全面，有的不够准确，甚至有的简直就是胡说八道。最近的项目正巧用到了这方面的知识，在这里做个总结。
环境：
Database: Oracle 9i
App Server: BEA Weblogic 8.14
表结构：
CREATE TABLE TESTBLOB (ID Int, NAME Varchar2(20), BLOBATTR Blob)
CREATE TABLE TESTBLOB (ID Int, NAME Varchar2(20), CLOBATTR Clob)
JAVA可以通过JDBC，也可以通过JNDI访问并操作数据库，这两种方式的具体操作存在着一些差异，由于通过App Server的数据库连接池JNDI获得的数据库连接提供的java.sql.Blob和java.sql.Clob实现类与JDBC方式提供的不同，因此在入库操作的时候需要分别对待；出库操作没有这种差异，因此不用单独对待。
一、BLOB操作
1、入库
（1）JDBC方式
//通过JDBC获得数据库连接
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();
//插入一个空对象empty_blob()
st.executeUpdate("insert into TESTBLOB (ID, NAME, BLOBATTR) values (1, "thename", empty_blob())");
//锁定数据行进行更新，注意“for update”语句
ResultSet rs = st.executeQuery("select BLOBATTR from TESTBLOB where ID=1 for update");
if (rs.next())
{
//得到java.sql.Blob对象后强制转换为oracle.sql.BLOB
oracle.sql.BLOB blob = (oracle.sql.BLOB) rs.getBlob("BLOBATTR");
OutputStream outStream = blob.getBinaryOutputStream();
//data是传入的byte数组，定义：byte[] data
outStream.write(data, 0, data.length);
}
outStream.flush();
outStream.close();
con.commit();
con.close();
（2）JNDI方式
//通过JNDI获得数据库连接
Context context = new InitialContext();
ds = (DataSource) context.lookup("ORA_JNDI");
Connection con = ds.getConnection();
con.setAutoCommit(false);
Statement st = con.createStatement();
//插入一个空对象empty_blob()
st.executeUpdate("insert into TESTBLOB (ID, NAME, BLOBATTR) values (1, "thename", empty_blob())");
//锁定数据行进行更新，注意“for update”语句
ResultSet rs = st.executeQuery("select BLOBATTR from TESTBLOB where ID=1 for update");
if (rs.next())
{
//得到java.sql.Blob对象后强制转换为weblogic.jdbc.vendor.oracle.OracleThinBlob（不同的App Server对应的可能会不同）
weblogic.jdbc.vendor.oracle.OracleThinBlob blob = (weblogic.jdbc.vendor.oracle.OracleThinBlob) rs.getBlob("BLOBATTR");
OutputStream outStream = blob.getBinaryOutputStream();
//data是传入的byte数组，定义：byte[] data
outStream.write(data, 0, data.length);
}
outStream.flush();
outStream.close();
con.commit();
con.close();
2、出库
//获得数据库连接
Connection con = ConnectionFactory.getConnection();
con.setAutoCommit(false);
Statement st = con.createStatement();
//不需要“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是读出并需要返回的数据，类型是byte[]
data = new byte;
inStream.read(data);
inStream.close();
}
inStream.close();
con.commit();
con.close();
二、CLOB操作
1、入库
（1）JDBC方式
//通过JDBC获得数据库连接
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();
//插入一个空对象empty_clob()
st.executeUpdate("insert into TESTCLOB (ID, NAME, CLOBATTR) values (1, "thename", empty_clob())");
//锁定数据行进行更新，注意“for update”语句
ResultSet rs = st.executeQuery("select CLOBATTR from TESTCLOB where ID=1 for update");
if (rs.next())
{
//得到java.sql.Clob对象后强制转换为oracle.sql.CLOB
oracle.sql.CLOB clob = (oracle.sql.CLOB) rs.getClob("CLOBATTR");
Writer outStream = clob.getCharacterOutputStream();
//data是传入的字符串，定义：String data
char[] c = data.toCharArray();
outStream.write(c, 0, c.length);
}
outStream.flush();
outStream.close();
con.commit();
con.close();
（2）JNDI方式
//通过JNDI获得数据库连接
Context context = new InitialContext();
ds = (DataSource) context.lookup("ORA_JNDI");
Connection con = ds.getConnection();
con.setAutoCommit(false);
Statement st = con.createStatement();
//插入一个空对象empty_clob()
st.executeUpdate("insert into TESTCLOB (ID, NAME, CLOBATTR) values (1, "thename", empty_clob())");
//锁定数据行进行更新，注意“for update”语句
ResultSet rs = st.executeQuery("select CLOBATTR from TESTCLOB where ID=1 for update");
if (rs.next())
{
//得到java.sql.Clob对象后强制转换为weblogic.jdbc.vendor.oracle.OracleThinClob（不同的App Server对应的可能会不同）
weblogic.jdbc.vendor.oracle.OracleThinClob clob = (weblogic.jdbc.vendor.oracle.OracleThinClob) rs.getClob("CLOBATTR");
Writer outStream = clob.getCharacterOutputStream();
//data是传入的字符串，定义：String data
char[] c = data.toCharArray();
outStream.write(c, 0, c.length);
}
outStream.flush();
outStream.close();
con.commit();
con.close();
2、出库
//获得数据库连接
Connection con = ConnectionFactory.getConnection();
con.setAutoCommit(false);
Statement st = con.createStatement();
//不需要“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是读出并需要返回的数据，类型是String
data = new String(c);
inStream.close();
}
inStream.close();
con.commit();
con.close();
需要注意的地方：
1、java.sql.Blob、oracle.sql.BLOB、weblogic.jdbc.vendor.oracle.OracleThinBlob几种类型的区别
2、java.sql.Clob、oracle.sql.CLOB、weblogic.jdbc.vendor.oracle.OracleThinClob几种类型的区别
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