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rx-java Observables for jdbc
package com.github.davidmoten.rx.jdbc;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import rx.Observable;
import rx.Observable.OnSubscribe;
import rx.Subscriber;
/**
* Executes the update query.
*/
class QueryUpdateOperation {
private static final Logger log = LoggerFactory.getLogger(QueryUpdateOperation.class);
static final String BEGIN_TRANSACTION = "begin";
/**
* Special sql command that brings about a rollback.
*/
static final String ROLLBACK = "rollback";
/**
* Special sql command that brings about a commit.
*/
static final String COMMIT = "commit";
/**
* Returns an Observable of the results of pushing one set of parameters
* through a select query.
*
* @param params
* one set of parameters to be run with the query
* @return
*/
static Observable execute(QueryUpdate query, List parameters) {
return Observable.create(new QueryUpdateOnSubscribe(query, parameters));
}
private static class QueryUpdateOnSubscribe implements OnSubscribe {
private boolean keepGoing = true;
/**
* The query to be executed.
*/
private final QueryUpdate query;
/**
* The parameters to run the query against (may be a subset of the query
* parameters specified in the query because the query may be run
* multiple times with multiple sets of parameters).
*/
private final List parameters;
/**
* Query connection.
*/
private Connection con;
/**
* Prepared statement for the query.
*/
private PreparedStatement ps;
/**
* Constructor.
*
* @param query
* @param parameters
*/
private QueryUpdateOnSubscribe(QueryUpdate query, List parameters) {
this.query = query;
this.parameters = parameters;
}
@Override
public void call(Subscriber subscriber) {
try {
if (isBeginTransaction())
performBeginTransaction(subscriber);
else {
getConnection();
if (isCommit())
performCommit(subscriber);
else if (isRollback())
performRollback(subscriber);
else
performUpdate(subscriber);
close();
}
complete(subscriber);
} catch (Exception e) {
try {
close();
} finally {
handleException(e, subscriber);
}
}
}
private boolean isBeginTransaction() {
return query.sql().equals(BEGIN_TRANSACTION);
}
private void performBeginTransaction(Subscriber subscriber) {
query.context().beginTransactionObserve();
log.debug("beginTransaction emitting 1");
subscriber.onNext(Integer.valueOf(1));
log.debug("emitted 1");
}
/**
* Gets the current connection.
*/
private void getConnection() {
log.debug("getting connection");
con = query.context().connectionProvider().get();
log.debug("cp={}", query.context().connectionProvider());
}
/**
* Returns true if and only if the sql statement is a commit command.
*
* @return if is commit
*/
private boolean isCommit() {
return query.sql().equals(COMMIT);
}
/**
* Returns true if and only if the sql statement is a rollback command.
*
* @return if is rollback
*/
private boolean isRollback() {
return query.sql().equals(ROLLBACK);
}
/**
* Commits the current transaction. Throws {@link RuntimeException} if
* connection is in autoCommit mode.
*
* @param subscriber
*/
private void performCommit(Subscriber subscriber) {
query.context().endTransactionObserve();
checkSubscription(subscriber);
if (!keepGoing)
return;
log.debug("committing");
Conditions.checkTrue(!Util.isAutoCommit(con));
Util.commit(con);
// must close before onNext so that connection is released and is
// available to a query that might process the onNext
close();
checkSubscription(subscriber);
if (!keepGoing)
return;
subscriber.onNext(Integer.valueOf(1));
log.debug("committed");
}
/**
* Rolls back the current transaction. Throws {@link RuntimeException}
* if connection is in autoCommit mode.
*
* @param subscriber
*/
private void performRollback(Subscriber subscriber) {
log.debug("rolling back");
query.context().endTransactionObserve();
Conditions.checkTrue(!Util.isAutoCommit(con));
Util.rollback(con);
// must close before onNext so that connection is released and is
// available to a query that might process the onNext
close();
subscriber.onNext(Integer.valueOf(0));
log.debug("rolled back");
}
/**
* Executes the prepared statement.
*
* @param subscriber
*
* @throws SQLException
*/
private void performUpdate(Subscriber subscriber) throws SQLException {
checkSubscription(subscriber);
if (!keepGoing)
return;
ps = con.prepareStatement(query.sql());
Util.setParameters(ps, parameters);
checkSubscription(subscriber);
if (!keepGoing)
return;
int count;
try {
log.debug("executing sql={}, parameters {}", query.sql(), parameters);
count = ps.executeUpdate();
log.debug("executed ps={}", ps);
} catch (SQLException e) {
throw new SQLException("failed to execute sql=" + query.sql(), e);
}
// must close before onNext so that connection is released and is
// available to a query that might process the onNext
close();
checkSubscription(subscriber);
if (!keepGoing)
return;
log.debug("onNext");
subscriber.onNext(count);
}
/**
* Notify observer that sequence is complete.
*
* @param subscriber
*/
private void complete(Subscriber subscriber) {
if (!subscriber.isUnsubscribed()) {
log.debug("onCompleted");
subscriber.onCompleted();
} else
log.debug("unsubscribed");
}
/**
* Notify observer of an error.
*
* @param e
* @param subscriber
*/
private void handleException(Exception e, Subscriber subscriber) {
log.debug("onError: ", e.getMessage());
if (subscriber.isUnsubscribed())
log.debug("unsubscribed");
else {
subscriber.onError(e);
}
}
/**
* Cancels a running PreparedStatement, closing it and the current
* Connection but only if auto commit mode.
*/
private void close() {
Util.closeQuietly(ps);
if (isCommit() || isRollback())
Util.closeQuietly(con);
else
Util.closeQuietlyIfAutoCommit(con);
}
private void checkSubscription(Subscriber subscriber) {
if (subscriber.isUnsubscribed()) {
keepGoing = false;
log.debug("unsubscribing");
}
}
}
}
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