Create OfflineValidator.java

integrations/java/src/main/java/de/licenseapi/OfflineValidator.java

@@ -0,0 +1,97 @@
+package de.licenseapi;
+
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import de.licenseapi.entities.License;
+import de.licenseapi.entities.LicenseStatus;
+
+import java.io.File;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.security.PublicKey;
+import java.time.Instant;
+import java.time.format.DateTimeFormatter;
+import java.util.Base64;
+
+public class OfflineValidator extends LicenseValidator {
+
+    private final PublicKey publicKey;
+
+    /**
+     * Creates a new offline validator
+     *
+     * @param publicKey The public key
+     */
+    public OfflineValidator(String publicKey) {
+        try {
+            this.publicKey = keyFromString(publicKey);
+        } catch (Exception e) {
+            throw new IllegalArgumentException("Invalid public key");
+        }
+    }
+
+    /**
+     * Retrieves the license from the license object, which can be obtained from the server.
+     * This will also run the signature verification and check if the license is expired.
+     *
+     * @param licenseObject The license object
+     * @return The license object represented as a {@link License}
+     */
+    public License retrieveLicenseFromString(String licenseObject) {
+        if (licenseObject == null) return null;
+
+        String base64 = licenseObject.replaceAll("(-----(BEGIN|END) LICENSE KEY-----|[\n\r])", "");
+
+        JsonObject object = JsonParser.parseString(new String(Base64.getDecoder().decode(base64),
+                StandardCharsets.UTF_8)).getAsJsonObject();
+
+        if (publicKey != null) {
+            String signature = object.get("signature").getAsString();
+            JsonObject data = object.getAsJsonObject("data");
+
+
+            try {
+                if (!verifyLicense(publicKey, signature, data.toString())) {
+                    return new License(LicenseStatus.INVALID_SIGNATURE, null, null, null, null, 0, null);
+                }
+
+                Instant instant = Instant.from(DateTimeFormatter.ISO_INSTANT.parse(data.get("renewalDate").getAsString()));
+
+                if (Instant.now().isAfter(instant)) {
+                    return new License(LicenseStatus.RENEWAL_REQUIRED, null, null, null, null, 0, null);
+                }
+
+                return parseLicense(data);
+            } catch (Exception e) {
+                return new License(LicenseStatus.INVALID_SIGNATURE, null, null, null, null, 0, null);
+            }
+        } else {
+            return parseLicense(object);
+        }
+    }
+
+    /**
+     * Retrieves the license from the license file
+     *
+     * @param licenseFile The license file
+     * @return The license object represented as a {@link License}
+     */
+    public License retrieveLicenseFromFile(File licenseFile) {
+        try {
+            return retrieveLicenseFromString(new String(Files.readAllBytes(licenseFile.toPath()), StandardCharsets.UTF_8));
+        } catch (Exception e) {
+            return null;
+        }
+    }
+
+    /**
+     * Retrieves the license from the license file
+     *
+     * @param licenseFilePath The path to the license file
+     * @return The license object represented as a {@link License}
+     */
+    public License retrieveLicenseFromFile(String licenseFilePath) {
+        return retrieveLicenseFromFile(new File(licenseFilePath));
+    }
+
+}