weblogic访问ORACLE，thin连接方式存取BLOB和CLOB字段（原创）

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Oracle Weblogic SQL JDBC SQL Server

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[STREAM_SIZE];
for (int i=0; i < STREAM_SIZE; i++) {
b[i] = (byte)(40 + (i%20)); // range 40-60
System.out.println("byte[" + i + "] = " + b[i]);
}
// 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[STREAM_SIZE];
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[STREAM_SIZE];
while ( rsreadblob.next() ) {
Blob myReadBlob =rsreadblob.getBlob("blobcol");
java.io.InputStream readis = myReadBlob.getBinaryStream();
for (int i=0 ; i < STREAM_SIZE ; i++) {
r[i] = (byte) readis.read();
System.out.println("output [" + i + "] = " + r[i]);
}
}
// 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[26];
for (int i=0 ; i < 26; i++) {
c[i] = (char) readClobis.read();
System.out.println("output [" + i + "] = " + c[i]);
}
}
// 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[input.available()];
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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2 楼 metallicats 2015-06-23

非常感谢博主！

1 楼 fshoy 2011-08-16

太感谢了！也希望这编好东西有更多人看到！！！

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