/**
* Initialises the state of this object. This is done lazily, because it requires the use of a
* database connection to discover the length of the clob, and that cannot be done while inside
* the ObjectStoreWriter while it has exclusive use of the connection.
*/
protected void init() {
if (results == null) {
Query q = new Query();
q.addToSelect(clob);
results = os.executeSingleton(q, 20, false, false, true);
int pageCount = results.size();
if (pageCount == 0) {
length = 0;
} else {
String lastPage = (String) results.get(pageCount - 1);
length = CLOB_PAGE_SIZE * (pageCount - 1) + lastPage.length();
}
}
}
/**
* Construct a ClobAccess object representing a subsequence of an existing ClobAccess object.
*
* @param results the SingletonResults object backing the object
* @param clob the Clob to access
* @param offset the offset
* @param length the length
*/
private ClobAccess(SingletonResults results, Clob clob, int offset, int length) {
this.results = results;
this.clob = clob;
this.offset = offset;
this.length = length;
os = results.getObjectStore();
subSequence = true;
}
/**
* Return a character from the specified index.
*
* @param index the position from which to return a character
* @return a character
* @throws IndexOutOfBoundsException if the index argument is negative or not less than length()
*/
public char charAt(int index) {
init();
if (index < 0) {
throw new IndexOutOfBoundsException("index is less than zero");
}
if (index >= length) {
throw new IndexOutOfBoundsException("index is not less than length");
}
int page = index / CLOB_PAGE_SIZE;
String pageText = (String) results.get(page);
return pageText.charAt(index - page * CLOB_PAGE_SIZE);
}
/**
* Sends the entire contents of the Clob into the given PrintStream. This method should be used in
* preference to toString() in order to save memory with large Clobs.
*
* @param out a PrintStream to write the Clob value to
*/
public void drainToPrintStream(PrintStream out) {
init();
int lowestPage = offset / CLOB_PAGE_SIZE;
int highestPage = (offset + length - 1) / CLOB_PAGE_SIZE;
for (int page = lowestPage; page <= highestPage; page++) {
String pageText = (String) results.get(page);
if (page == highestPage) {
pageText = pageText.substring(0, offset + length - page * CLOB_PAGE_SIZE);
}
if (page == lowestPage) {
pageText = pageText.substring(offset - page * CLOB_PAGE_SIZE, pageText.length());
}
out.print(pageText);
}
}
/**
* Converts the Clob into a String. Be careful that it can fit in memory!
*
* @return a String
*/
@Override
public String toString() {
init();
StringBuilder retval = new StringBuilder();
if (length > 0) {
int lowestPage = offset / CLOB_PAGE_SIZE;
int highestPage = (offset + length - 1) / CLOB_PAGE_SIZE;
for (int page = lowestPage; page <= highestPage; page++) {
String pageText = (String) results.get(page);
if (page == highestPage) {
pageText = pageText.substring(0, offset + length - page * CLOB_PAGE_SIZE);
}
if (page == lowestPage) {
pageText = pageText.substring(offset - page * CLOB_PAGE_SIZE, pageText.length());
}
retval.append(pageText);
}
}
return retval.toString();
}
