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This lesson demonstrates a basic JDBC read: connect a Java application to a local PostgreSQL database, query a products table, and print its rows. The example uses DriverManager; its sample credentials and code are for learning, not a production configuration.
What the example does
In Saravanan Lakshmanan’s DEV Community lesson, DBConnection.getPSQLConnection() calls DriverManager.getConnection with the URL jdbc:postgresql://localhost:5432/productdb, the username postgres, and a password literal in the source. The URL targets a PostgreSQL server on the same machine, using port 5432 and a database named productdb. The database and its products table must already exist for the query to succeed. The article excerpt does not specify the Java version, PostgreSQL version, JDBC driver dependency or version, or database setup instructions. Read the lesson on DEV Community.
How the product read works
The lesson’s ProductService.viewProduct() obtains the connection, prepares select * from products, executes the query, and iterates over the resulting ResultSet. For each row it reads the id, name, category, and price columns. This is the basic JDBC read path: a connection provides access to the database, a statement runs the SQL, and the result set exposes returned rows.
The indexed article output reports a successful connection and shows two illustrative rows: 1 / chair / furniture / 10000 and 2 / mobile / electronics / 20000. These are the lesson’s example output, not a guarantee about what a reader’s database will contain.
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What you need to adapt before running it
- Use your own database details. The hostname, port, database name, username, and password must match your PostgreSQL setup. JDBC URL syntax is database-specific; Oracle’s tutorial notes that each DBMS specifies its URL format. Oracle JDBC: Connecting with the
DriverManagerclass. - Supply a compatible PostgreSQL JDBC driver. The lesson excerpt does not identify a driver artifact or version, so it does not establish a complete dependency setup.
- Confirm the expected schema. The query expects a table named
productswith columnsid,name,category, andprice. The excerpt does not provide table-creation SQL. - Do not deploy the literal credentials. Keep secrets outside source code and load them from configuration appropriate to your environment. Avoid printing passwords or other secrets while diagnosing connection failures.
Improve the sample for an application
Select only the columns you use
select * from products is compact for demonstrating iteration, but a real query should name the required fields, for example select id, name, category, price from products. Explicit columns make the query’s data needs clear and avoid fetching unrelated fields.
Close JDBC resources reliably
The indexed code does not show the connection, statement, or result set inside try-with-resources blocks. In reusable Java code, manage these resources with try-with-resources so they close when processing finishes or an exception occurs.
Keep useful error details
The lesson catches SQLException and prints a generic message. That is visible to a beginner but does not explain whether the problem is an unreachable server, invalid credentials, a missing database, or a query/schema issue. Retain the exception for controlled diagnostics—such as recording an appropriate error and its cause—while ensuring credentials and other secrets are not logged. The Java SE 26 DriverManager API documents that getConnection can throw SQLException for a database access error. Java SE 26 DriverManager API.
When to use DriverManager or DataSource
DriverManager is a straightforward way to illustrate connecting with a database URL and access details. For application connection management, Oracle’s JDBC tutorial prefers DataSource, explaining: “This interface is preferred over DriverManager because it allows details about the underlying data source to be transparent to your application.” The right choice depends on whether you need a small, direct learning example or a more separated approach to connection configuration and management. Oracle JDBC: Connecting with the DriverManager class.
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