oracle处理clob数据
以下方法为 OracleDAOUtil中的方法。
1. 插入记录
private static void insert(String id, Connection connection) {
Connection conn = null;
PreparedStatement stmt = null;
String sql = "";
try {
sql = "insert into Test (ID,Value) values(?,empty_clob())"; //先插入空的CLOB对象
conn = connection;
stmt = conn.prepareStatement(sql);
int count = 0;
stmt.setString(++count, id);
stmt.execute();
OracleDAOUtil.updateField(conn, "Test", "ID", id, "Value", "abcd"); //写入数据
} catch (Exception e) {
e.printStackTrace();
throw e;
} finally {
try {
if (stmt != null) {
stmt.close();
stmt = null;
}
} catch (Exception ex) {
}
try {
if (conn != null) {
conn = null;
}
} catch (Exception ex) {
}
}
}
2. 向CLOB字段写入数据
public static void updateField(Connection conn, String tableName, String keyName, String keyValue, String fieldName, String fieldValue) throws WorkflowException
{
PreparedStatement pstmt = null;
PreparedStatement pstmt2 = null;
ResultSet rset = null;
try {
String sql = "select " + fieldName + " from " + tableName + " where " + keyName + "=? for update";
pstmt = conn.prepareStatement(sql);
pstmt.setString(1, keyValue);
rset = pstmt.executeQuery();
Clob clob = null;
if (rset.next())
clob = (Clob) rset.getClob(1);
String value = fieldValue;
if (value == null)
value = "";
char[] valueChars = new char[value.length()];
value.getChars(0,value.length(),valueChars,0);
clob.truncate(0); //避免前一次的数据混在第二次的数据中（如果上次的数据比本次的数据多的话）
Writer writer = clob.setCharacterStream(0);
writer.write(valueChars);
writer.close();
} catch (Exception e) {
throw e;
} finally {
if (rset != null) {
try {
rset.close();
rset = null;
} catch (SQLException e) {
throw e;
}
}
if (pstmt != null) {
try {
pstmt.close();
pstmt = null;
} catch (SQLException e) {
throw e;
}
}
if (pstmt2 != null) {
try {
pstmt2.close();
pstmt2 = null;
} catch (SQLException e) {
throw e;
}
}
}
}
3. 从CLOB字段读数据
public static String readField(Connection conn, String tableName, String keyName, String keyValue, String fieldName) throws WorkflowException
{
String value = "";
PreparedStatement pstmt = null;
ResultSet rset = null;
try {
String sql = "select " + fieldName + " from " + tableName + " where " + keyName + "=?";
pstmt = conn.prepareStatement(sql);
pstmt.setString(1, keyValue);
rset = pstmt.executeQuery();
Clob clob = null;
if (rset.next())
clob = (Clob) rset.getClob(1);
if (clob != null) {
int len = (int) clob.length();
char[] buffer = new char[len];
Reader reader = clob.getCharacterStream();
reader.read(buffer);
reader.close();
value = new String(buffer);
}
return value;
} catch (Exception e) {
throw e;
} finally {
if (rset != null) {
try {
rset.close();
rset = null;
} catch (SQLException e) {
throw e;
}
}
if (pstmt != null) {
try {
pstmt.close();
pstmt = null;
} catch (SQLException e) {
throw e;
}
}
}
}
以上方法稍作改进就可用于处理BLOB字段。
如果使用Oracle提供的JDBC驱动来处理CLOB和BLOB字段，那么使用Oracle 10g的版本，Oracle 9i的版本对CLOB和BLOB的处理有问题。Oracle 10g JDBC的thin模式也可用于Oracle 9i。