Why does BouncyCastle throw NoClassDefFoundError?

[terlan98]

I'm trying to create a PDF signing demo using iText. My code depends on org.bouncycastle, which I have also force-linked in robovm.xml. I use the following command to create an Xcode framework from my Java code: mvn -Drobovm.enableBitcode=true compile robovm:install. I have a signPDF function that is supposed to sign the given PDF. The function throws a NoClassDefFoundError when I run it on an iOS device.

public static String signPdf(String base64Pdf, String base64PrivateKey, String base64Certificate) {
        try {
            setupBouncyCastle();

            byte[] pdfBytes = Base64.decodeBase64(base64Pdf.getBytes());
            byte[] privateKeyBytes = Base64.decodeBase64(base64PrivateKey.getBytes());
            byte[] certBytes = Base64.decodeBase64(base64Certificate.getBytes());

            PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(privateKeyBytes);
            KeyFactory keyFactory = KeyFactory.getInstance("RSA");
            PrivateKey privateKey = keyFactory.generatePrivate(keySpec);

            CertificateFactory certFactory = CertificateFactory.getInstance("X.509");
            X509Certificate cert = (X509Certificate) certFactory.generateCertificate(new ByteArrayInputStream(certBytes));

            PdfReader reader = new PdfReader(new ByteArrayInputStream(pdfBytes));
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            PdfWriter writer = new PdfWriter(baos);

            PdfSigner signer = new PdfSigner(reader, writer, new StampingProperties().useAppendMode());
            IExternalSignature pks = new PrivateKeySignature(privateKey, DigestAlgorithms.SHA256, CounterService.provider.getName());
            IExternalDigest digest = new BouncyCastleDigest();

            signer
                    .setReason("Test")
                    .setLocation("Test")
                    .setPageRect(new Rectangle(0, 0, 200, 100))
                    .setPageNumber(1)
                    .setFieldName("Test_" + System.currentTimeMillis());

            signer.signDetached(digest, pks, new X509Certificate[]{cert}, null, null, null, 0, PdfSigner.CryptoStandard.CADES);

            writer.close();
            reader.close();

            String result = Arrays.toString(Base64.encodeBase64(baos.toByteArray()));
            System.out.println("✅ Sign Successful " + result);
            return result;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

Console output:

java.lang.NoClassDefFoundError: java.util.function.Supplier
	at java.lang.VMClassLoader.findClassInClasspathForLoader(Native Method)
	at java.lang.PathClassLoader.findClass(PathClassLoader.java:193)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:515)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:475)
	at com.itextpdf.bouncycastleconnector.BouncyCastleFactoryCreator.populateFactoriesMap(BouncyCastleFactoryCreator.java:108)
	at com.itextpdf.bouncycastleconnector.BouncyCastleFactoryCreator.<clinit>(BouncyCastleFactoryCreator.java:52)
	at com.itextpdf.signatures.DigestAlgorithms.<clinit>(DigestAlgorithms.java:118)
	at com.itextpdf.signatures.PrivateKeySignature.<init>(PrivateKeySignature.java:89)
	at com.itextpdf.signatures.PrivateKeySignature.<init>(PrivateKeySignature.java:72)
	at org.robovm.samples.myjavaframework.CounterService.signPdf(CounterService.java:124)
	at org.robovm.samples.myjavaframework.CounterService.increase(CounterService.java:67)

My robovm.xml file:

<config>
    <os>ios</os>
    <arch>arm64</arch>
    <arch>thumbv7</arch>
    <target>framework</target>
    <imageName>${framework.name}</imageName>
    <infoPList>Info.plist.xml</infoPList>
    <treeShaker>aggressive</treeShaker>
    <forceLinkClasses>
        <pattern>java.io.ByteArrayInputStream</pattern>
        <pattern>java.io.ByteArrayOutputStream</pattern>
        <pattern>java.io.IOException</pattern>
        <pattern>java.security.KeyFactory</pattern>
        <pattern>java.security.PrivateKey</pattern>
        <pattern>java.security.Provider</pattern>
        <pattern>java.security.Security</pattern>
        <pattern>java.security.cert.CertificateFactory</pattern>
        <pattern>java.security.cert.X509Certificate</pattern>
        <pattern>java.security.spec.PKCS8EncodedKeySpec</pattern>

        <pattern>org.robovm.samples.myjavaframework.**</pattern>

        <pattern>com.itextpdf.signatures.PdfSigner</pattern>
        <pattern>com.itextpdf.signatures.IExternalSignature</pattern>
        <pattern>com.itextpdf.signatures.DigestAlgorithms</pattern>
        <pattern>com.itextpdf.signatures.IExternalDigest</pattern>
        <pattern>com.itextpdf.signatures.PrivateKeySignature</pattern>
        <pattern>com.itextpdf.signatures.BouncyCastleDigest</pattern>
        <pattern>com.itextpdf.bouncycastleconnector.**</pattern>

        <pattern>com.android.org.conscrypt.OpenSSLProvider</pattern>
        <pattern>com.android.org.conscrypt.OpenSSLRandom</pattern>
        <pattern>com.android.org.conscrypt.OpenSSLBIOInputStream</pattern>

        <pattern>org.bouncycastle.**</pattern>

        <pattern>java.util.logging.**</pattern>
    </forceLinkClasses>
    <exportedSymbols>
        <symbol>JNI_CreateJavaVM</symbol>
    </exportedSymbols>
</config>

My pom.xml file:

<?xml version="1.0"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.robovm</groupId>
        <artifactId>robovm-samples-parent</artifactId>
        <version>1.0</version>
    </parent>

    <artifactId>robovm-samples-dynamiclib</artifactId>
    <name>RoboVM dynamic library sample</name>

    <packaging>jar</packaging>

    <repositories>
        <repository>
            <id>central</id>
            <name>Maven Central</name>
            <url>https://repo1.maven.org/maven2/</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>oss-sonatype</id>
            <name>oss-sonatype</name>
            <url>https://oss.sonatype.org/content/repositories/snapshots/</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
    </repositories>

    <dependencies>
        <dependency>
            <groupId>com.itextpdf.android</groupId>
            <artifactId>kernel-android</artifactId>
            <version>8.0.3</version>
        </dependency>
        <dependency>
            <groupId>com.itextpdf.android</groupId>
            <artifactId>layout-android</artifactId>
            <version>8.0.3</version>
        </dependency>
        <dependency>
            <groupId>com.itextpdf.android</groupId>
            <artifactId>sign-android</artifactId>
            <version>8.0.3</version>
        </dependency>
        <dependency>
            <groupId>com.itextpdf.android</groupId>
            <artifactId>bouncy-castle-adapter-android</artifactId>
            <version>8.0.3</version>
        </dependency>
        <dependency>
            <groupId>com.itextpdf.android</groupId>
            <artifactId>bouncy-castle-connector-android</artifactId>
            <version>8.0.3</version>
        </dependency>

        <dependency>
            <groupId>xerces</groupId>
            <artifactId>xercesImpl</artifactId>
            <version>2.12.2</version>
        </dependency>
        <dependency>
            <groupId>xml-apis</groupId>
            <artifactId>xml-apis</artifactId>
            <version>1.4.01</version>
        </dependency>

        <dependency>
            <groupId>com.mobidevelop.robovm</groupId>
            <artifactId>robovm-rt</artifactId>
            <version>2.3.21</version>
        </dependency>
    </dependencies>
</project>

[dkimitsa]

current version of MobiVM is Android 4,4 based which means its stuck at java7 level.
java.util.function.Supplier class is part of Function API that was added in Java8 and not completely available.
your option is either use older Bouncy Castle or not use it at all and generate certificates with available in RoboVM libraries.
there is an experimental build with Android12 runtime https://github.com/robovmx/robovmx/releases, you can give it a try.
but it was not updated for a while

[terlan98]

Thanks! I'll give the experimental build a try

[terlan98]

The experimental build fixed the issue. Thanks again!

[dkimitsa]

@terlan98 have updated experimental build with all changes from MobiVM.
https://github.com/robovmx/robovmx/releases/tag/x2-libcore12-v10.2.2.3-20240416