关于com.typesafe.config读取自定义对象及配置创建的技术咨询

Great question! Let’s tackle this one step at a time.

Yes, you’re absolutely right! The Lightbend Config library (formerly Typesafe Config) provides built-in methods to parse values into basic types like Integer, Boolean, String, and collections—but it doesn’t offer out-of-the-box support for directly resolving config values into custom objects. Its core focus is on handling hierarchical, flexible config data, leaving object mapping to either manual implementation or third-party libraries.

First, let’s structure your desired config using HOCON (Human-Optimized Config Object Notation), the default format for Lightbend Config. Save this as application.conf in your project’s classpath:

cookie {
  cookieName = "id"
  cookiePath = "/"
  cookieDomain = null  # Represents "None" in your requirement
  secureCookie = true
  httpOnlyCookie = true
  useFingerprinting = true
  cookieMaxAge = 86400  # Example: 1 day in seconds; adjust as needed
}

Note: In HOCON, null is used to represent an absent/None value, which aligns with your cookieDomain = None requirement.

Since there’s no native method for this, you have two common, practical approaches:

Option 1: Manual mapping (no third-party dependencies) #

First, define your custom object class (Java example; the approach is nearly identical for Scala):

public class CookieConfig {
    private String cookieName;
    private String cookiePath;
    private String cookieDomain; // Null represents "None"
    private boolean secureCookie;
    private boolean httpOnlyCookie;
    private boolean useFingerprinting;
    private int cookieMaxAge;

    // Constructor
    public CookieConfig(String cookieName, String cookiePath, String cookieDomain,
                        boolean secureCookie, boolean httpOnlyCookie,
                        boolean useFingerprinting, int cookieMaxAge) {
        this.cookieName = cookieName;
        this.cookiePath = cookiePath;
        this.cookieDomain = cookieDomain;
        this.secureCookie = secureCookie;
        this.httpOnlyCookie = httpOnlyCookie;
        this.useFingerprinting = useFingerprinting;
        this.cookieMaxAge = cookieMaxAge;
    }

    // Getters (add setters if needed)
    public String getCookieName() { return cookieName; }
    public String getCookiePath() { return cookiePath; }
    public String getCookieDomain() { return cookieDomain; }
    public boolean isSecureCookie() { return secureCookie; }
    public boolean isHttpOnlyCookie() { return httpOnlyCookie; }
    public boolean isUseFingerprinting() { return useFingerprinting; }
    public int getCookieMaxAge() { return cookieMaxAge; }
}

Then, read the config and map it to your custom object:

import com.typesafe.config.Config;
import com.typesafe.config.ConfigFactory;

public class ConfigLoader {
    public static void main(String[] args) {
        // Load the main config file
        Config rootConfig = ConfigFactory.load();
        // Extract the cookie-specific sub-config
        Config cookieConfig = rootConfig.getConfig("cookie");

        // Manually map config values to your custom object
        CookieConfig customCookieConfig = new CookieConfig(
            cookieConfig.getString("cookieName"),
            cookieConfig.getString("cookiePath"),
            // Handle the "None" case: check if the path exists and isn't null
            cookieConfig.hasPath("cookieDomain") && !cookieConfig.isNull("cookieDomain")
                ? cookieConfig.getString("cookieDomain")
                : null,
            cookieConfig.getBoolean("secureCookie"),
            cookieConfig.getBoolean("httpOnlyCookie"),
            cookieConfig.getBoolean("useFingerprinting"),
            cookieConfig.getInt("cookieMaxAge")
        );

        // Use your custom object as needed
        System.out.println("Cookie name: " + customCookieConfig.getCookieName());
    }
}

Option 2: Use Jackson for automatic mapping (third-party library) #

If you want to avoid repetitive manual mapping, use Jackson’s jackson-datatype-config module, which integrates seamlessly with Lightbend Config.

First, add the dependency (Maven example):

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-config</artifactId>
    <version>2.15.2</version> <!-- Use the latest stable version -->
</dependency>

Update your CookieConfig class to include a default constructor (required by Jackson) or use Jackson annotations:

public class CookieConfig {
    private String cookieName;
    private String cookiePath;
    private String cookieDomain;
    private boolean secureCookie;
    private boolean httpOnlyCookie;
    private boolean useFingerprinting;
    private int cookieMaxAge;

    // Default constructor for Jackson
    public CookieConfig() {}

    // Getters and setters (Jackson requires these for deserialization)
    public String getCookieName() { return cookieName; }
    public void setCookieName(String cookieName) { this.cookieName = cookieName; }
    public String getCookiePath() { return cookiePath; }
    public void setCookiePath(String cookiePath) { this.cookiePath = cookiePath; }
    public String getCookieDomain() { return cookieDomain; }
    public void setCookieDomain(String cookieDomain) { this.cookieDomain = cookieDomain; }
    public boolean isSecureCookie() { return secureCookie; }
    public void setSecureCookie(boolean secureCookie) { this.secureCookie = secureCookie; }
    public boolean isHttpOnlyCookie() { return httpOnlyCookie; }
    public void setHttpOnlyCookie(boolean httpOnlyCookie) { this.httpOnlyCookie = httpOnlyCookie; }
    public boolean isUseFingerprinting() { return useFingerprinting; }
    public void setUseFingerprinting(boolean useFingerprinting) { this.useFingerprinting = useFingerprinting; }
    public int getCookieMaxAge() { return cookieMaxAge; }
    public void setCookieMaxAge(int cookieMaxAge) { this.cookieMaxAge = cookieMaxAge; }
}

Then, use Jackson to deserialize the config directly into your custom object:

import com.fasterxml.jackson.databind.ObjectMapper;
import com.typesafe.config.Config;
import com.typesafe.config.ConfigFactory;
import com.fasterxml.jackson.datatype.config.ConfigModule;

public class JacksonConfigLoader {
    public static void main(String[] args) throws Exception {
        Config rootConfig = ConfigFactory.load();
        Config cookieConfig = rootConfig.getConfig("cookie");

        ObjectMapper objectMapper = new ObjectMapper();
        // Register the Lightbend Config module for Jackson
        objectMapper.registerModule(new ConfigModule());

        // Deserialize the config into your custom object
        CookieConfig customCookieConfig = objectMapper.readValue(cookieConfig.root(), CookieConfig.class);

        // Use your object
        System.out.println("Cookie domain: " + customCookieConfig.getCookieDomain());
    }
}

内容的提问来源于stack exchange，提问作者Manu Chadha