If you read a value that is later rolled back, you will have read an invalid value. How locks are set is determined by what is called a transaction isolation level, which can range from not supporting transactions at all to supporting transactions that enforce very strict access rules. The interface Connection includes five values that represent the transaction isolation levels you can use in JDBC:. A non-repeatable read occurs when transaction A retrieves a row, transaction B subsequently updates the row, and transaction A later retrieves the same row again.
Transaction A retrieves the same row twice but sees different data. A phantom read occurs when transaction A retrieves a set of rows satisfying a given condition, transaction B subsequently inserts or updates a row such that the row now meets the condition in transaction A, and transaction A later repeats the conditional retrieval. Transaction A now sees an additional row. This row is referred to as a phantom. Usually, you do not need to do anything about the transaction isolation level; you can just use the default one for your DBMS.
The default transaction isolation level depends on your DBMS. If a driver does not support the isolation level specified in an invocation of setTransactionIsolation , the driver can substitute a higher, more restrictive transaction isolation level.
If a driver cannot substitute a higher transaction level, it throws a SQLException. Use the method DatabaseMetaData. The method Connection. The Connection. However, if the new price is greater than a specified price, maximumPrice , then the price is reverted to the original price:. The following statement specifies that the cursor of the ResultSet object generated from the getPrice query is closed when the commit method is called.
Post as a guest Name. Email Required, but never shown. The Overflow Blog. Podcast Making Agile work for data science. Stack Gives Back Featured on Meta. New post summary designs on greatest hits now, everywhere else eventually.
Linked Related Hot Network Questions. Question feed. Stack Overflow works best with JavaScript enabled. Accept all cookies Customize settings. In addition to the features highlighted above, this release also includes a substantial number of bug fixes and enhancements:.
The following are known issues and changes that have been identified as potentially affecting users of EclipseLink 2. When running EclipseLink 2. Java hotspot compiler may crash when compiling org.
EclipseLink remains focused on delivering support for the latest standards. Please make sure you read and understood the documentation that comes with this software.
The documentation explains about the most common problems encountered and contains information about the license this software is covered by. By using this software you agree to the terms and conditions laid down in the license.
For a quick start the license is provided in the "license" directory in text format. As it seems there are situations where people cannot agree to the license. Please contact us to discuss the terms and conditions for a commercial license. Use the address mentioned at the bottom of the file.
This may be useful to find our which files have changed since you last updated the software.
0コメント