dummysignaturehandler.java

来自「Java生成PDF Java生成PDF Java生成PDF」· Java 代码 · 共 92 行

import org.faceless.pdf2.*;
import java.io.*;
import java.util.zip.CRC32;
import java.security.KeyStore;
import java.security.GeneralSecurityException;

/**
 * This simple class shows how to create a SignatureHandler class
 * that verifies the document using a CRC-32 checksum.
 */
public class DummySignatureHandler extends SignatureHandler
{
    public DummySignatureHandler()
    {
        super();
    }

    public String getFilter()
    {
        return "Dummy.CRC32";
    }

    protected void prepareToSign(KeyStore store, String alias, char[] password)
        throws GeneralSecurityException
    {
        // not using a keystore in this example, so just ignore them.
        super.prepareToSign(store, alias, password);
        putNumericValue("Version", 1);	// Add some values to the signature dictionary
    }

    public byte[] sign(InputStream in)
    {
        CRC32 crc = new CRC32();
        int b;
	try {
	    while ((b=in.read())>=0) {
		crc.update(b);
	    }
	} catch (IOException e) {
	    throw new RuntimeException("Unexpected IOException!");
	}
	int val = (int)crc.getValue();
        byte[] out = new byte[4];
        out[0]=(byte)(val>>24);
        out[1]=(byte)(val>>16);
        out[2]=(byte)(val>>8);
        out[3]=(byte)(val);
        return out;
    }

    public boolean verify(InputStream in)
    {
        CRC32 crc = new CRC32();
        int b;
	try {
	    while ((b=in.read())>=0) {
		crc.update(b);
	    }
	} catch (IOException e) {
	    throw new RuntimeException("Unexpected IOException!");
	}
        int val = (int)crc.getValue();
        byte[] buf = getStringValue("Contents");
        return val == ((buf[0]<<24 & 0xff000000) +
                       (buf[1]<<16 & 0xff0000) +
                       (buf[2]<<8 & 0xff00) +
                       (buf[3] & 0xff));
    }
    
    public String[] getLayerNames()
    {
        final String[] names = { "n0" };
        return names;
    }

    public PDFCanvas getLayerAppearance(String name, PDFStyle style)
    {
	if (name.equals("n0")) {
	    PDFCanvas canvas = new PDFCanvas(100, 100);
	    canvas.setStyle(style);
	    LayoutBox box = new LayoutBox(80);
	    box.addTextNoBreak("CRC-32", style, null);
	    canvas.drawLayoutBox(box, 10, 50);
	    return canvas;
	} else {
	    // This will never happen, as we're specifying the only layer is "n0"
	    // in the method above. Still, it's an example so we'll do it properly.
	    throw new IllegalArgumentException("Unknown layer '"+name+"' requested");
	}
    }
}