SmgService.java

package com.lmco.spectrum.systemnavigation3d.service;

import com.amazonaws.util.IOUtils;
import com.lmco.spectrum.systemnavigation3d.util.io.SfxZipInputStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import javax.annotation.Nullable;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
import java.util.zip.ZipOutputStream;

@Service
public class SmgService {

    private static final Logger log = LoggerFactory.getLogger(SmgService.class);
    private static final String PRODUCT_XML = "product.smgXml";

    @Autowired
    TransformationService transformationService;

    // Max capacity is 2^31-1 bytes or ~2GB.
    @Nullable
    public byte[] processSmg(byte[] data){
        Map<String, byte[]> entryMap = getSmgXmlEntry(data);
        byte[] smgXmlData = entryMap.get(PRODUCT_XML);
        if(smgXmlData != null) {
            String smgXml = new String(smgXmlData);
            smgXml = transformationService.transform(smgXml);
            entryMap.put(PRODUCT_XML, smgXml.getBytes()); // Update XML entry.
            return repackageSmg(entryMap);
        } else {
            return null;
        }
    }

    public Map<String, byte[]> getSmgXmlEntry(byte[] data) {

        Map<String, byte[]> entryMap = new HashMap<>();

        try(ZipInputStream zis = new ZipInputStream(new SfxZipInputStream(new ByteArrayInputStream(data)))) {

            ZipEntry entry;
            while((entry = zis.getNextEntry()) != null) {
                entryMap.put(entry.getName(), IOUtils.toByteArray(zis));
                zis.closeEntry();
            }
            return entryMap;

        } catch (IOException e) {
            log.error("Failed to read .smgXml entry!");
            e.printStackTrace();
        }

        return entryMap;
    }

    @Nullable
    public byte[] repackageSmg(Map<String, byte[]> entryMap) {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        try (ZipOutputStream zos = new ZipOutputStream(bos)) {
            for(Map.Entry<String, byte[]> entry : entryMap.entrySet()) {
                ZipEntry zipEntry = new ZipEntry(entry.getKey());
                zos.putNextEntry(zipEntry);
                zos.write(entry.getValue());
                zos.closeEntry();
            }
        } catch (IOException e) {
            log.error("Failed to repackage smg file");
            e.printStackTrace();
            return null;
        }

        return bos.toByteArray();

    }

}