🤔 Как организовать подключение к базе данных, обеспечить журналирование в сервлете?

1⃣Добавьте зависимости в pom.xml:

<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.25</version>
</dependency>

2⃣Подключение к базе данных в сервлете:

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DatabaseServlet extends HttpServlet {
    private static final String DB_URL = "jdbc:mysql://localhost:3306/mydatabase";
    private static final String USER = "root";
    private static final String PASS = "password";

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        try (Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);
             Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery("SELECT id, name FROM Users")) {
            while (rs.next()) {
                response.getWriter().println("ID: " + rs.getInt("id") + ", Name: " + rs.getString("name"));
            }
        } catch (Exception e) {
            e.printStackTrace(response.getWriter());
        }
    }
}

🚩Журналирование (логирование):

1⃣Добавьте зависимости в pom.xml:

<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-api</artifactId>
    <version>2.14.1</version>
</dependency>
<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <version>2.14.1</version>
</dependency>

2⃣Файл конфигурации log4j2.xml:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %c{1} - %msg%n"/>
        </Console>
        <File name="File" fileName="logs/app.log">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %c{1} - %msg%n"/>
        </File>
    </Appenders>
    <Loggers>
        <Root level="debug">
            <AppenderRef ref="Console"/>
            <AppenderRef ref="File"/>
        </Root>
    </Loggers>
</Configuration>

3⃣Использование логгера в сервлете:

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

public class LoggingServlet extends HttpServlet {
    private static final Logger logger = LogManager.getLogger(LoggingServlet.class);

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        logger.info("Processing GET request");
        response.getWriter().println("Check the logs for output");
    }
}

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