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

{

/* 设定不自动提交 */

boolean defaultCommit = conn.getAutoCommit();

conn.setAutoCommit(false);

try {

/* 插入一个空的CLOB对像 */

stmt.executeUpdate("INSERT INTO TEST_CLOB VALUES ('111', EMPTY_CLOB())");

/* 查询此CLOB对象并锁定 */

ResultSet rs = stmt.executeQuery("SELECT CLOBCOL FROM TEST_CLOB WHERE ID='111' FOR UPDATE");

while (rs.next()) {

/* 取出此CLOB对像 */

oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");

/* 向CLOB对像中写入数据 */

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();

}

/* 正式提交 */

conn.commit();

} catch (Exception ex) {

/* 出错回滚 */

conn.rollback();

throw ex;

}

/* 恢复原提交状态 */

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

{

/* 设定不自动提交 */

boolean defaultCommit = conn.getAutoCommit();

conn.setAutoCommit(false);

try {

/* 查询CLOB对象并锁定 */

ResultSet rs = stmt.executeQuery("SELECT CLOBCOL FROM TEST_CLOB WHERE ID='111' FOR UPDATE");

while (rs.next()) {

/* 获取此CLOB对像 */

oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");

/* 进行覆盖式修改 */

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();

}

/* 正式提交 */

conn.commit();

} catch (Exception ex) {

/* 出错回滚 */

conn.rollback();

throw ex;

}

/* 恢复原提交状态 */

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

{

/* 设定不自动提交 */

boolean defaultCommit = conn.getAutoCommit();

conn.setAutoCommit(false);

try {

/* 清空原CLOB对像 */

stmt.executeUpdate("UPDATE TEST_CLOB SET CLOBCOL=EMPTY_CLOB() WHERE ID='111'");

/* 查询CLOB对象并锁定 */

ResultSet rs = stmt.executeQuery("SELECT CLOBCOL FROM TEST_CLOB WHERE ID='111' FOR UPDATE");

while (rs.next()) {

/* 获取此CLOB对像 */

oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");

/* 更新数据 */

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();

}

/* 正式提交 */

conn.commit();

} catch (Exception ex) {

/* 出错回滚 */

conn.rollback();

throw ex;

}

/* 恢复原提交状态 */

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

{

/* 设定不自动提交 */

boolean defaultCommit = conn.getAutoCommit();

conn.setAutoCommit(false);

try {

/* 查询CLOB对像 */

ResultSet rs = stmt.executeQuery("SELECT * FROM TEST_CLOB WHERE ID='111'");

while (rs.next()) {

/* 获取CLOB对像 */

oracle.sql.CLOB clob = (oracle.sql.CLOB)rs.getClob("CLOBCOL");

/* 以字符形式输出 */

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;

}

/* 恢复原提交状态 */

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

{

/* 设定不自动提交 */

boolean defaultCommit = conn.getAutoCommit();

conn.setAutoCommit(false);

try {

/* 插入一个空的BLOB对像 */

stmt.executeUpdate("INSERT INTO TEST_BLOB VALUES ('222', EMPTY_BLOB())");

/* 查询此BLOB对象并锁定 */

ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERE ID='222' FOR UPDATE");

while (rs.next()) {

/* 取出此BLOB对像 */

oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");

/* 向BLOB对像中写入数据 */

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();

}

/* 正式提交 */

conn.commit();

} catch (Exception ex) {

/* 出错回滚 */

conn.rollback();

throw ex;

}

/* 恢复原提交状态 */

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

{

/* 设定不自动提交 */

boolean defaultCommit = conn.getAutoCommit();

conn.setAutoCommit(false);

try {

/* 查询BLOB对象并锁定 */

ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERE ID='222' FOR UPDATE");

while (rs.next()) {

/* 取出此BLOB对像 */

oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");

/* 向BLOB对像中写入数据 */

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();

}

/* 正式提交 */

conn.commit();

} catch (Exception ex) {

/* 出错回滚 */

conn.rollback();

throw ex;

}

/* 恢复原提交状态 */

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

{

/* 设定不自动提交 */

boolean defaultCommit = conn.getAutoCommit();

conn.setAutoCommit(false);

try {

/* 清空原BLOB对像 */

stmt.executeUpdate("UPDATE TEST_BLOB SET BLOBCOL=EMPTY_BLOB() WHERE ID='222'");

/* 查询此BLOB对象并锁定 */

ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERE ID='222' FOR UPDATE");

while (rs.next()) {

/* 取出此BLOB对像 */

oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");

/* 向BLOB对像中写入数据 */

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();

}

/* 正式提交 */

conn.commit();

} catch (Exception ex) {

/* 出错回滚 */

conn.rollback();

throw ex;

}

/* 恢复原提交状态 */

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

{

/* 设定不自动提交 */

boolean defaultCommit = conn.getAutoCommit();

conn.setAutoCommit(false);

try {

/* 查询BLOB对像 */

ResultSet rs = stmt.executeQuery("SELECT BLOBCOL FROM TEST_BLOB WHERE ID='222'");

while (rs.next()) {

/* 取出此BLOB对像 */

oracle.sql.BLOB blob = (oracle.sql.BLOB)rs.getBlob("BLOBCOL");

/* 以二进制形式输出 */

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();

}

/* 正式提交 */

conn.commit();

} catch (Exception ex) {

/* 出错回滚 */

conn.rollback();

throw ex;

}

/* 恢复原提交状态 */

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。