Java 17 Recipes

 How It Works
The same basic code format is used for performing just about every database task. The 
format is as follows.
1. Obtain a connection to the database.
2. Create a statement from the connection.
3. Perform a database task with the statement.
4. Do something with the results of the database task.
5. Close the statement (and database connection if you’re finished 
using it).
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The main difference between performing a query using JDBC and DML is that you 
call different methods on the Statement object, depending on which operation you 
want to perform. To perform a query, you need to call the Statement executeQuery() 
method. To perform DML tasks such as insert, update, and delete, call the 
executeUpdate() method.
The performCreate() method in the solution to this recipe demonstrates inserting 
a record into a database. To insert a record in the database, construct a SQL INSERT 
statement in string format. To perform the insert, pass the SQL string to the Statement 
object’s executeUpdate() method. If the INSERT is performed, an int value is returned 
that specifies the number of rows that have been inserted. If the INSERT operation is not 
performed successfully, either a zero is returned, or SQLException is thrown, indicating 
a problem with the statement or database connection.
The performRead() method in the solution to this recipe demonstrates querying 
the database. To execute a query, call the Statement object’s executeQuery() method, 
passing a SQL statement in string format. The result is a ResultSet object, which can 
then work with the returned data. For more information on performing queries, see 
Recipe 12-4.
The performUpdate() method in the solution to this recipe demonstrates updating 
records within a database table. First, construct a SQL UPDATE statement in string format. 
Next, to perform the update operation, pass the SQL string to the Statement object’s 
executeUpdate() method. If the UPDATE is successfully performed, an int value is 
returned, which specifies the number of updated records. If the UPDATE operation is not 
performed successfully, either a zero is returned, or SQLException is thrown, indicating 
a problem with the statement or database connection.
The last database operation that needs to be covered is the DELETE operation. The 
performDelete() method in the solution to this recipe demonstrates deleting records 
from the database. First, construct a SQL DELETE statement in string format. Next, to 
execute the deletion, pass the SQL string to the Statement object’s executeUpdate() 
method. If the deletion is successful, an int value specifying the number of rows deleted 
is returned. Otherwise, if the deletion fails, a zero is returned, or SQLException is thrown, 
indicating a problem with the statement or database connection.
Almost every database application uses at least one of the CRUD operations at 
some point. This is foundational JDBC that needs to be known if you are working with 
databases within Java applications. Even if you do not work directly with the JDBC API, it 
is good to know these foundational basics.
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