LOB类型分为BLOB和CLOB两种：BLOB即二进制大型对像（Binary Large Object），适用于存贮非文本的字节流数据（如程序、图像、影音等）。而CLOB，即字符型大型对像（Character Large Object），则与字符集相关，适于存贮文本型的数据（如歷史档案、大部头著作等）。
下面以程序实例说明通过JDBC操纵Oracle数据库LOB类型字段的几种情况。
先建立如下两个测试用的数据库表，Power Designer PD模型如下：
建表SQL语句为：
CREATE TABLE TEST_CLOB ( ID NUMBER(3), CLOBCOL CLOB)
CREATE TABLE TEST_BLOB ( ID NUMBER(3), BLOBCOL BLOB)
一、 CLOB对象的存取
1、往数据库中插入一个新的CLOB对像
复制代码 代码如下:
public static void clobInsert(String infile) throws Exception
{
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
stmt.executeUpdate("INSERT INTO TEST_CLOB VALUES ('111', EMPTY_CLOB())");
ResultSet rs = stmt.executeQuery("SELECT CLOBCOL FROM TEST_CLOB WHERe ID='111' FOR UPDATe");
while (rs.next()) {
oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");
BufferedWriter out = new BufferedWriter(clob.getCharacterOutputStream());
BufferedReader in = new BufferedReader(new FileReader(infile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
conn.commit();
} catch (Exception ex) {
conn.rollback();
throw ex;
}
conn.setAutoCommit(defaultCommit);
}
2、修改CLOB对像（是在原CLOB对像基础上进行覆盖式的修改）
复制代码 代码如下:
public static void clobModify(String infile) throws Exception
{
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
ResultSet rs = stmt.executeQuery("SELECT CLOBCOL FROM TEST_CLOB WHERe ID='111' FOR UPDATe");
while (rs.next()) {
oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");
BufferedWriter out = new BufferedWriter(clob.getCharacterOutputStream());
BufferedReader in = new BufferedReader(new FileReader(infile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
conn.commit();
} catch (Exception ex) {
conn.rollback();
throw ex;
}
conn.setAutoCommit(defaultCommit);
}
3、替换CLOB对像（将原CLOB对像清除，换成一个全新的CLOB对像）
复制代码 代码如下:
public static void clobReplace(String infile) throws Exception
{
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
stmt.executeUpdate("UPDATE TEST_CLOB SET CLOBCOL=EMPTY_CLOB() WHERe ID='111'");
ResultSet rs = stmt.executeQuery("SELECT CLOBCOL FROM TEST_CLOB WHERe ID='111' FOR UPDATe");
while (rs.next()) {
oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");
BufferedWriter out = new BufferedWriter(clob.getCharacterOutputStream());
BufferedReader in = new BufferedReader(new FileReader(infile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
conn.commit();
} catch (Exception ex) {
conn.rollback();
throw ex;
}
conn.setAutoCommit(defaultCommit);
}
4、CLOB对像读取
复制代码 代码如下:
public static void clobRead(String outfile) throws Exception
{
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
ResultSet rs = stmt.executeQuery("SELECT * FROM TEST_CLOB WHERe ID='111'");
while (rs.next()) {
oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");
BufferedReader in = new BufferedReader(clob.getCharacterStream());
BufferedWriter out = new BufferedWriter(new FileWriter(outfile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
out.close();
in.close();
}
} catch (Exception ex) {
conn.rollback();
throw ex;
}
conn.setAutoCommit(defaultCommit);
}
二、 BLOB对象的存取
1、 向数据库中插入一个新的BLOB对像
复制代码 代码如下:
public static void blobInsert(String infile) throws Exception
{
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
stmt.executeUpdate("INSERT INTO TEST_BLOB VALUES ('222', EMPTY_BLOB())");
ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERe ID='222' FOR UPDATe");
while (rs.next()) {
oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");
BufferedOutputStream out = new BufferedOutputStream(blob.getBinaryOutputStream());
BufferedInputStream in = new BufferedInputStream(new FileInputStream(infile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
conn.commit();
} catch (Exception ex) {
conn.rollback();
throw ex;
}
conn.setAutoCommit(defaultCommit);
}
2、修改BLOB对像（是在原BLOB对像基础上进行覆盖式的修改）
复制代码 代码如下:
public static void blobModify(String infile) throws Exception
{
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERe ID='222' FOR UPDATe");
while (rs.next()) {
oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");
BufferedOutputStream out = new BufferedOutputStream(blob.getBinaryOutputStream());
BufferedInputStream in = new BufferedInputStream(new FileInputStream(infile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
conn.commit();
} catch (Exception ex) {
conn.rollback();
throw ex;
}
conn.setAutoCommit(defaultCommit);
}
3、替换BLOB对像（将原BLOB对像清除，换成一个全新的BLOB对像）
复制代码 代码如下:
public static void blobReplace(String infile) throws Exception
{
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
stmt.executeUpdate("UPDATE TEST_BLOB SET BLOBCOL=EMPTY_BLOB() WHERe ID='222'");
ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERe ID='222' FOR UPDATe");
while (rs.next()) {
oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");
BufferedOutputStream out = new BufferedOutputStream(blob.getBinaryOutputStream());
BufferedInputStream in = new BufferedInputStream(new FileInputStream(infile));
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
conn.commit();
} catch (Exception ex) {
conn.rollback();
throw ex;
}
conn.setAutoCommit(defaultCommit);
}
4、BLOB对像读取
复制代码 代码如下:
public static void blobRead(String outfile) throws Exception
{
boolean defaultCommit = conn.getAutoCommit();
conn.setAutoCommit(false);
try {
ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERe ID='222'");
while (rs.next()) {
oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");
BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(outfile));
BufferedInputStream in = new BufferedInputStream(blob.getBinaryStream());
int c;
while ((c=in.read())!=-1) {
out.write(c);
}
in.close();
out.close();
}
conn.commit();
} catch (Exception ex) {
conn.rollback();
throw ex;
}
conn.setAutoCommit(defaultCommit);
}
观察上述程序对LOB类型字段的存取，我们可以看出，较之其它类型字段，有下面几个显著不同的特点：
一是必须取消自动提交。
