Confused about setting the value of @transactional

Question

Can anybody explain me that when I should put readOnly value as true and when I should set it as false when using it with @Transactional ?

Answer 1

When you are only reading/selecting from the database and not changing any data - by performing an update/insert/delete.

If you can specify readOnly you should as its much less resource intensive.

Answer 2

the definition is pretty straight-forward: You may use readonly=true if and only if you assure no update, insert or delete operation takes place inside the transaction. This optimizes the locking behaviour of your dbms, if supported.

readonly is false by default.

best regards,

sam

Edit

/**
 * {@code true} if the transaction is read-only.
 * Defaults to {@code false}.
 * <p>This just serves as a hint for the actual transaction subsystem;
 * it will <i>not necessarily</i> cause failure of write access attempts.
 * A transaction manager which cannot interpret the read-only hint will
 * <i>not</i> throw an exception when asked for a read-only transaction.
 * @see org.springframework.transaction.interceptor.TransactionAttribute#isReadOnly()
 */
boolean readOnly() default false;

Answer 3

Customizing the isolation level you add more control to your transactions.

If you know that a method will be read-only you should specify it.

With readonly=true you are saying to the transaction manager that one particular method will only read from the DB. This has two advantages:

First, it can be faster than the others, because it allows the DBMS to optimize the transaction (if supported). Secondly it could save you from deadlock problems (when for example a specific table is write-locked), because you are assuring that the method won't execute INSERT or UPDATE.

However, here you can find all the details about it: http://docs.spring.io/spring/docs/2.5.x/reference/transaction.html