OCP 8 – working with autocommit vs savepoints

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OCP 8 – working with autocommit vs savepoints

November 26th, 2016 by Jeanne Boyarsky

You might want to know more about JDBC than is covered by Chapter 10 of our book, OCP: Oracle Certified Professional Java SE 8 Programmer II Study Guide: Exam 1Z0-809. This blog post teaches you about autocommit and savepoints and assumes you have completed reading chapter 10 of our OCP 8 book and are looking to learn more. (Note: we’ve heard rumors this topic is in fact on the exam. It wasn’t when we took the beta but was on the Java 7 exam. So either the questions are left over or it was added back.)

In the book, you saw how to run one statement at a time and have the database automatically see the changes right away. This is called automatic commit or auto-commit for short. A commit updates the database. JDBC provides options for more control by running your code in transactions. A transaction allows a group of statements to go together.

Rollback/Commit

By default, auto-commit is set to true which means each statement is committed in the database as soon as it is run. You can set it to false so statements and prepared statements do not automatically commit data.

The following example gives that control. If anything goes wrong update either of the rows, the entire transaction is rolled back and the database doesn’t change either row. If both are successful, the database sees both.

conn.setAutoCommit(false);
String sql = "update species name = ? where id = ?";
PreparedStatement ps = conn.prepareStatement(sql);
try {
  ps.setString(1, "Elephant");
  ps.setInt(2, 1);
  ps.executeUpdate();
  ps.setString(1, "Monkey");
  ps.setInt(2, 4);
  ps.executeUpdate();
  
  conn.commit();      // send data to database
} catch (SQLException e) {
  conn.rollback();    // don't update database
}

Let’s rewrite this example to focus more on the commit/rollback code:

conn.setAutoCommit(false);
String sql = "update species name = ? where id = ?";
PreparedStatement ps = conn.prepareStatement(sql);
try {
  updateRecord(1);
  updateRecord(2);
  conn.commit(); // send data to database 
} catch (SQLException e) {
  conn.rollback(); // don't update database 
} 

Setting a Rollback point

JDBC has a type called a Savepoint which is like putting a bookmark in a book so you can easily get back there.

conn.setAutoCommit(false);
String sql = "update species name = ? where id = ?";
PreparedStatement ps = conn.prepareStatement(sql);
try {
  updateRecord(1);
  Savepoint sp = conn.setSavepoint();
  updateRecord(2);
  updateRecord(3);
  // oops - let's go back like this didn't happen
  conn.rollback(sp);
  // proceed from there
  updateRecord(4);
  conn.commit(); // send data to database 
} catch (SQLException e) { 
  conn.rollback(); // don't update database 
} 

Announcing: Our NEW Java OCA / OCP 8 Practice Test Book!

November 3rd, 2016 by Scott Selikoff
pt-cover

Jeanne and I are thrilled and excited to announce that we are nearly done writing a brand new book for the OCA / OCP Java 8 Programmer exams!

The new book, OCA / OCP Java SE 8 Programmer Practice Tests, includes over 1000+ hand-crafted and peer reviewed questions. We’ve also created a new permanent Practice Tests OCA / OCP 8 book page on the blog to keep track of updates and news about the new book.

Jeanne and I wanted to say how thankful we are to our all of our readers of our first two books. Without your invaluable feedback and positive reviews, we never would have been offered this opportunity to expand our OCA and OCP subject matter. We promise to make this next book our best yet!

We are expecting to ship the book in March 2017. Stay tuned for additional news about the book!

What is a DDOS? Explaining it to your grandmother

October 24th, 2016 by Jeanne Boyarsky

After Friday’s internet attack, I had to explain what a DDOS (Distributed Denial of Service) attack was to my mother. She’s not so good with computers which is why her computer is a Chromebook. Here’s what I came up with:

Imagine I ring your doorbell and then run around the corner. You answer the door, but nobody is there. I do this every hour for six hours. Annoying right? Now imagine I recruit 100 people to do the same thing. Now your doorbell is ringing every 30 seconds. Eek! That’s a DDOS.

What do you think? Good analogy?