What are the exception handling mechanisms for Java database connections?

The database connection exception handling mechanism in Java includes try-catch blocks, try-with-resources statements and methods provided by the JDBC API. These mechanisms can be used to handle SQLException and IOException exceptions and to troubleshoot by obtaining information such as error codes, SQL status codes, and error messages.

Java database connection exception handling mechanism

Introduction

Connect in Java When accessing the database, you may encounter various abnormal situations. To handle these exceptions, Java provides several exception handling mechanisms.

Exception type

Database connection exceptions can be divided into two categories:

• SQLException: represents operations related to the database Related exceptions.
• IOException: Indicates an exception related to input/output operations, such as network connection problems with the database.

Exception handling

There are several ways to handle database connection exceptions:

1. try-catch block

The try-catch block is the most common exception handling mechanism. The syntax is as follows:

try {
    // 数据库操作代码
} catch (SQLException ex) {
    // 处理 SQLException
} catch (IOException ex) {
    // 处理 IOException
}

2. try-with-resources statement

try-with-resources statement automatically closes resources, including database connections. The syntax is as follows:

try (Connection conn = DriverManager.getConnection(...)) {
    // 数据库操作代码
}

Practical case

The following code example demonstrates how to use a try-catch block to handle SQLException:

import java.sql.*;

public class DBConnect {

    public static void main(String[] args) {
        try {
            // 连接数据库
            Connection conn = DriverManager.getConnection("...");

            // 执行查询
            Statement stmt = conn.createStatement();
            ResultSet rs = stmt.executeQuery("...");

            // 遍历结果集
            while (rs.next()) {
                // 处理结果
            }
        } catch (SQLException ex) {
            // 处理数据库异常
            ex.printStackTrace();
        }
    }
}

3. Java Database Connectivity (JDBC) API

The JDBC API provides specific methods for handling database connection exceptions:

• getErrorCode(): Get error code.
• getSQLState(): Get the SQL status code.
• getMessage(): Get the error message.

Troubleshooting

Here are some troubleshooting tips:

• Check that the database connection string is correct.
• Make sure the database is running and accepting connections.
• Check whether the Java application has the necessary database driver dependencies.
• Check the network connection between the database server and the Java application.

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