17 - Java in the Real World

Java in the Real World

Moving from theory to practice requires knowing the best practices for structuring professional projects: logging, configuration, environment management.

Related deep dive: 16 - Build Tools: Maven e Gradle.

Related deep dive: 18 - Preparazione Framework Enterprise.

Project Structure

my-project/
├── src/
│   ├── main/
│   │   ├── java/
│   │   │   └── com/example/
│   │   │       ├── Application.java
│   │   │       ├── config/
│   │   │       ├── controller/
│   │   │       ├── service/
│   │   │       ├── repository/
│   │   │       ├── model/
│   │   │       └── util/
│   │   └── resources/
│   │       ├── application.properties
│   │       ├── application-dev.properties
│   │       ├── application-prod.properties
│   │       └── logback.xml
│   └── test/
│       ├── java/
│       └── resources/
├── pom.xml (or build.gradle)
└── README.md

Logging

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class UserService {
    private static final Logger logger = LoggerFactory.getLogger(UserService.class);

    public User findUser(Long id) {
        logger.debug("Searching for user with ID: {}", id);

        try {
            User user = repository.findById(id);
            logger.info("User found: {}", user.getName());
            return user;
        } catch (UserNotFoundException e) {
            logger.warn("User not found: {}", id);
            throw e;
        } catch (Exception e) {
            logger.error("Error while searching for user", e);
            throw new ServiceException("Internal error", e);
        }
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>%d{HH:mm:ss} [%thread] %-5level %logger{36} - %msg%n</pattern>
        </encoder>
    </appender>

    <appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
        <file>logs/app.log</file>
        <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy">
            <fileNamePattern>logs/app.%d{yyyy-MM-dd}.log</fileNamePattern>
            <maxHistory>30</maxHistory>
        </rollingPolicy>
        <encoder>
            <pattern>%d [%thread] %-5level %logger - %msg%n</pattern>
        </encoder>
    </appender>

    <root level="INFO">
        <appender-ref ref="CONSOLE" />
        <appender-ref ref="FILE" />
    </root>

    <logger name="com.example" level="DEBUG" />
</configuration>

Configuration

# Database
db.url=jdbc:postgresql://localhost:5432/mydb
db.username=user
db.password=password
db.pool.size=10

# API
api.timeout.ms=5000
api.retry.count=3

# Feature flags
feature.newUi.enabled=true

import java.io.*;
import java.util.Properties;

public class ConfigurationManager {
    private static final Properties props = new Properties();

    static {
        String env = System.getProperty("app.env", "dev");
        String filename = "application-" + env + ".properties";

        try (InputStream is = ConfigurationManager.class
                .getClassLoader().getResourceAsStream(filename)) {
            if (is != null) {
                props.load(is);
            }
        } catch (IOException e) {
            throw new RuntimeException("Unable to load configuration", e);
        }
    }

    public static String get(String key) {
        return props.getProperty(key);
    }

    public static int getInt(String key, int defaultValue) {
        String value = props.getProperty(key);
        return value != null ? Integer.parseInt(value) : defaultValue;
    }

    public static boolean getBoolean(String key) {
        return Boolean.parseBoolean(props.getProperty(key));
    }
}

// Usage
String dbUrl = ConfigurationManager.get("db.url");
int timeout = ConfigurationManager.getInt("api.timeout.ms", 3000);

Best Practices