Java JDBC: Connecting to Relational Databases
Jul 05, 2025 am 01:11 AM
To correctly connect to the database through JDBC, first introduce the driver package of the corresponding database, such as MySQL's mysql-connector-java; secondly, use the correct URL format, such as jdbc:mysql://localhost:3306/mydb, and pay attention to the correctness of parameters, hostname and port; then write code to obtain connections and handle exceptions, it is recommended to use configuration files to store username and password, and capture SQLException to provide meaningful prompts; finally be sure to close the connection resources, and it is recommended to use try-with-resources to automatically manage it. Follow these steps to effectively avoid common problems and ensure stable connections.
Connecting to a database is simple and simple, but when you really have to write code, many people will still be stuck with some details of JDBC. This article mainly talks about how to correctly connect to a relational database through JDBC with Java, focusing on processes and precautions.
Introducing the appropriate JDBC driver
JDBC itself is just an interface, and what really works is the driver implementation provided by various database manufacturers. So the first step is to make sure that your project has the corresponding database driver package.
For example, if you want to connect to MySQL, you need to add dependencies like this in the Maven project:
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.33</version>
</dependency>If you are using other databases, such as PostgreSQL or Oracle, remember to change to the corresponding driver name and version.
Notice:
- The driver version is best compatible with the JDK version you use.
- The drivers of some databases (such as Oracle) may not be in the central repository and need to be manually downloaded and installed to the local repository.
Connect to the database using the correct URL format
The JDBC URLs of each database are written slightly differently, and the format is usually as follows:
jdbc:<database type>://<hostname>:<port>/<database name>? Parameters
For example, the connection string of MySQL may be:
String url = "jdbc:mysql://localhost:3306/mydb?useSSL=false&serverTimezone=UTC";
Common pitfalls:
- Forgot to add parameters such as
?useSSL=false, resulting in the connection failure; - The host name or port is written incorrectly, especially the remote database;
- The database service is not started, or the firewall does not open the corresponding port.
Get the connection and handle the exception
The typical code structure for connecting to a database is as follows:
Connection conn = null;
try {
conn = DriverManager.getConnection(url, username, password);
// Perform database operations...
} catch (SQLException e) {
e.printStackTrace();
// Handle exceptions, such as prompting the user to check the network or configuration}Several suggestions:
- Do not hard-code usernames and passwords in the code, you can use configuration files or environment variables;
- It is safer to automatically close resources using try-with-resources (Java 7);
- Be careful to catch SQLException and give meaningful error prompts instead of throwing the stack directly.
Close the connection and don't let the resource leak
Many people just focus on opening the connection and forget to close it. This will cause the connection pool to run out and even the database to crash.
The connection should be closed in order after use:
- ResultsSet
- Statement / PreparedStatement
- Connection
The recommended method is to automatically close it in try-with-resources, for example:
try (Connection conn = DriverManager.getConnection(url, username, password);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM users")) {
while (rs.next()) {
System.out.println(rs.getString("name"));
}
} catch (SQLException e) {
e.printStackTrace();
}This will prevent you from forgetting to close the resources and will be simpler.
Basically that's it. Although JDBC is original, it is still useful in many scenarios. Mastering the basic process and common problems can help you avoid many pitfalls.
The above is the detailed content of Java JDBC: Connecting to Relational Databases. For more information, please follow other related articles on the PHP Chinese website!
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