"Calling JAVA From C"
Vol. 9, Issue 8, p. 38

	



Listing 1: Java code to list contents of a zip file

1	import java.util.zip.*;
2	import java.util.Enumeration;
3	
4	ZipFile zf = new ZipFile(zipFileName);
5	Enumeration entries = zf.entries();
6	while(entries.hasMoreElements())
7	{
8	   String entry = ((ZipEntry)(entries.nextElement())).getName();
9	}

Listing 2: Excerpt of C code to list contents of zip file

1	int zipEntry(char *csEntryName)
2	{
3	   jboolean isException;
4	   jstring jsEntryName;
5	   jobject oZipEntry = (*jni)->CallObjectMethod(jni, oZipEntries,
6	      midEnumNextElement);
7	   isException = checkException();
8	   if (isException || oZipEntry == NULL) return 0;
9	
10	   jsEntryName = (*jni)->CallObjectMethod(jni, oZipEntry, midZipGetName);
11	   isException = checkException();
12	   if (isException || jsEntryName == NULL) return 0;
13	   else
14	   {
15	      const char *tempData =(*jni)->GetStringUTFChars(jni, jsEntryName, 0);
16	      isException = checkException();
17	      if (tempData == NULL || isException) return 0;
18	
19	      // copy to caller's buffer and release the UTF
20	      strcpy(csEntryName, (char*)tempData);
21	      (*jni)->ReleaseStringUTFChars(jni, jsEntryName, tempData); 
22	      isException = checkException();
23	      return (!isException);
24	   }
25	}

Listing 3: CJProxy

1	package cj;
2	
3	public interface CJProxy
4	{
5	   public Object execute(Object args) throws Exception;
6	}

Listing 4: Java zip proxy

1	package cj.example;
2	
3	import cj.CJProxy;
4	import java.io.*;
5	import java.util.zip.*;
6	import java.util.Enumeration;
7	
8	/**
9	 * CJZipList is a CJProxy that lists the entries in a zip file.
10	 */
11	public class CJZipList implements CJProxy
12	{
13	   /**
14	    * Proxy execute takes a string with the name of the zip file.
15	    * It returns a pipe-delimited string with the list of entries 
16	    * in the zip file.
17	    */
18	   public Object execute(Object args) throws Exception
19	   {
20	      if (!(args instanceof String))
21	      {
22	         throw new RuntimeException("Invalid type for execute");
23	      }
24	
25	      StringBuffer retbuf = new StringBuffer("");
26	      ZipFile zf = new ZipFile((String)args);
27	      Enumeration entries = zf.entries();
28	      while(entries.hasMoreElements())
29	      {
30	         String entry = ((ZipEntry)(entries.nextElement())).getName();
31	         retbuf.append(entry);
32	         retbuf.append("|");
33	      }
34	
35	      return retbuf.toString();
36	   }
37	}