Moved transactions out of database component.

briar-api/src/org/briarproject/api/db/Transaction.java

@@ -1,15 +1,38 @@
 package org.briarproject.api.db;
 
-/** A wrapper around a database transaction. */
+/**
+ * A wrapper around a database transaction. Transactions are not thread-safe.
+ */
 public class Transaction {
 
 	private final Object txn;
+	private boolean complete = false;
 
 	public Transaction(Object txn) {
 		this.txn = txn;
 	}
 
+	/**
+	 * Returns the database transaction. The type of the returned object
+	 * depends on the database implementation.
+	 */
 	public Object unbox() {
 		return txn;
 	}
+
+	/**
+	 * Returns true if the transaction is ready to be committed.
+	 */
+	public boolean isComplete() {
+		return complete;
+	}
+
+	/**
+	 * Marks the transaction as ready to be committed. This method must not be
+	 * called more than once.
+	 */
+	public void setComplete() {
+		if (complete) throw new IllegalStateException();
+		complete = true;
+	}
 }