Zxing - java.lang.LinkageError:违反加载器约束

Question

我想在我的ejb bean中使用外部jars (Zxing，Batik)，根据this thread的说法，我将jars添加到了EarContent/lib中，一切似乎都很正常。我的ejb-bean如下所示：

@Stateless
public class ManageBarcodeBean implements ...{
    ...
    @Override
    public String createQrCode(String text, Dimension dim, ErrorCorrectionLevel errCorr) {
        ...
        try {
            ...
            if (Math.max(dim.getWidth(), dim.getHeight()) <= 1000) {
                //*
                QRCodeWriter qrCodeWriter = new QRCodeWriter();
                //**
                BitMatrix bm = qrCodeWriter.encode(text, BarcodeFormat.QR_CODE, dim.getWidth(), dim.getHeight(), hints);
                //67
                BufferedImage imgBuf = MatrixToImageWriter.toBufferedImage(bm);
                ...
            }
            ...
        } catch (Exception e) {
            ...
        } 
        return null;
    }
    ...
}

在我添加行\\ 67之前，一切都很正常，但是添加下面这一行会产生以下结果：

Caused by: java.lang.LinkageError:

loader constraint violation:

when resolving method
"com.google.zxing.client.j2se.MatrixToImageWriter.toBufferedImage(Lcom/google/zxing/common/BitMatrix;)Ljava/awt/image/BufferedImage;"

the class loader (instance of org/glassfish/javaee/full/deployment/EarClassLoader) 

of the current class, de/lsanet/lav/address/beans/ManageBarcodeBean,

and the class loader (instance of com/sun/enterprise/loader/CurrentBeforeParentClassLoader)

for the method's defining class, com/google/zxing/client/j2se/MatrixToImageWriter,

have different Class objects for the type com/google/zxing/common/BitMatrix

used in the signature at
de.lsanet.lav.address.beans.ManageBarcodeBean.createQrCode(ManageBarcodeBean.java:67)

我找到了this payara solution并添加了

<classloading-delegate>false</classloading-delegate>

解决了这个问题，但我不明白，为什么在*和**上访问外部jar-1 (Zxing：core-3.3.2.jar)能很好地工作，而在67上访问外部jar-2 (Zxing：javase-3.3.2.jar)就不行了。

我不希望影响容器的类加载策略。

Answer 1

正如tsolakp假设的那样，java.lang.LinkageError的原因是com.google.zxing.common.BitMatrix的两个版本。错误地，我将相同的jar放在了${domain_dir}/lib和EARContent/lib中。