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
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
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)
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)
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
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
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)
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)
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
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);
}
一是必须取消自动提交。
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