我有一项任务是从Oracle 9i数据库中读取CLOB文件并将其写入文件。我对小文件有用,但在文件较大的情况下,大约200MB这对于一个文件需要大约5个小时,这是完全不可接受的。我相信这可以更快完成,但我不知道如何。这就是我所拥有的:
//get the Clob record from the database and convert it to String
public String getClobRecord() {
Connection conn;
Clob xmlCont;
ResultSet rset;
PreparedStatement stmt;
try {
conn = db.prepareConn();
String sql = "select a.clob_clm from xml_statement a where period_id = ?";
stmt = conn.prepareStatement(sql);
stmt.setInt(1, pid);
rset = stmt.executeQuery();
while (rset.next()) {
xmlCont = rset.getClob(1);
xml = ClobStringConversion(xmlCont);
}
stmt.close();
DBConnect.closeConn(conn);
} catch (SQLException asd) {
log.fatal(asd.getMessage());
} catch (IOException asd) {
log.fatal(asd.getMessage());
}
return xml;
}
//My CLOB to String Conversion Method
public static String ClobStringConversion(Clob clb) throws SQLException, IOException {
if (clb == null) {
return "";
}
StringBuilder str = new StringBuilder();
String strng;
BufferedReader br = new BufferedReader(clb.getCharacterStream());
while ((strng = br.readLine()) != null) {
str.append(strng);
}
return str.toString();
}
//Write the String to File
public void writeXmlToFile(String fileDir, String xmlFileName) {
File xmlfile = new File(fileDir + "/" + xmlFileName);
xml = this.getClobRecord();
try {
BufferedWriter bw = new BufferedWriter(new FileWriter(xmlfile));
bw.write(formatXmlFile());
bw.close();
} catch (IOException asd) {
log.fatal(asd.getMessage());
}
}
我应该更改为容纳非常大的CLOB文件?
答案 0 :(得分:1)
如果你坚持将clob数据存储在内存中,你可以改进的一件事就是使用特定于oracle的功能。
public static String toString(final Clob clob)
throws SQLException, IOException {
if (clob == null) {
return "";
}
Long length = null;
// try to get the oracle specific CLOB length
// no vendor-specific code here.
try {
final Class<?> oracleClobClass = Class.forName("oracle.sql.CLOB");
if (oracleClobClass.isInstance(clob)) {
length = (Long) oracleClobClass.getMethod("getLength", null)
.invoke(clob, null);
}
} catch (final Exception e) {
}
// we can set initial capacity if we got the length.
final StringBuilder builder
= length == null
? new StringBuilder() : new StringBuilder(length.intValue());
final BufferedReader reader
= new BufferedReader(clob.getCharacterStream());
for (String line = null; (line = reader.readLine()) != null; ) {
builder.append(line);
}
return builder.toString();
}