diff --git a/src/main/org/apache/tools/ant/taskdefs/SignJar.java b/src/main/org/apache/tools/ant/taskdefs/SignJar.java
index 3e8503474..e975f4061 100644
--- a/src/main/org/apache/tools/ant/taskdefs/SignJar.java
+++ b/src/main/org/apache/tools/ant/taskdefs/SignJar.java
@@ -54,13 +54,20 @@
 package org.apache.tools.ant.taskdefs;
 
 import java.io.File;
+import java.io.IOException;
+import java.util.Enumeration;
+import java.util.Vector;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipFile;
 import org.apache.tools.ant.*;
 import org.apache.tools.ant.types.Commandline;
+import org.apache.tools.ant.types.FileSet;
 
 /**
  * Sign a archive.
- * 
+ *
  * @author Peter Donald <a href="mailto:donaldp@apache.org">donaldp@apache.org</a>
+ * @author Nick Fortescue <a href="mailto:nick@ox.compsoc.net">nick@ox.compsoc.net</a>
  */
 public class SignJar extends Task {
 
@@ -87,142 +94,223 @@ public class SignJar extends Task {
     protected boolean internalsf;
     protected boolean sectionsonly;
 
+    /**
+     * the filesets of the jars to sign
+     */
+    protected Vector filesets = new Vector();
+    /**
+     * Whether to assume a jar which has an appropriate .SF file in is already
+     * signed.
+     */
+    protected boolean lazy;
+
     public void setJar(final String jar) {
         this.jar = jar;
-    } 
+    }
 
     public void setAlias(final String alias) {
         this.alias = alias;
-    } 
+    }
 
     public void setKeystore(final String keystore) {
         this.keystore = keystore;
-    } 
+    }
 
     public void setStorepass(final String storepass) {
         this.storepass = storepass;
-    } 
+    }
 
     public void setStoretype(final String storetype) {
         this.storetype = storetype;
-    } 
+    }
 
     public void setKeypass(final String keypass) {
         this.keypass = keypass;
-    } 
+    }
 
     public void setSigfile(final String sigfile) {
         this.sigfile = sigfile;
-    } 
+    }
 
     public void setSignedjar(final String signedjar) {
         this.signedjar = signedjar;
-    } 
+    }
 
     public void setVerbose(final boolean verbose) {
         this.verbose = verbose;
-    } 
+    }
 
     public void setInternalsf(final boolean internalsf) {
         this.internalsf = internalsf;
-    } 
+    }
 
     public void setSectionsonly(final boolean sectionsonly) {
         this.sectionsonly = sectionsonly;
-    } 
+    }
+
+    public void setLazy(final boolean lazy) {
+        this.lazy = lazy;
+    }
+
+    /**
+     * Adds a set of files (nested fileset attribute).
+     */
+    public void addFileset(final FileSet set) {
+        filesets.addElement(set);
+    }
+
 
     public void execute() throws BuildException {
+        if (null == jar && null == filesets) {
+            throw new BuildException("jar must be set through jar attribute or nested filesets");
+        }
+        if( null != jar ) {
+            doOneJar(jar, signedjar);
+            return;
+        } else {
+            //Assume null != filesets
+
+            // deal with the filesets
+            for (int i=0; i<filesets.size(); i++) {
+                FileSet fs = (FileSet) filesets.elementAt(i);
+                DirectoryScanner ds = fs.getDirectoryScanner(project);
+                String[] jarFiles = ds.getIncludedFiles();
+                for(int j=0; j<jarFiles.length; j++) {
+                    doOneJar(jarFiles[j], null);
+                }
+            }
+        }
+    }
+
+    private void doOneJar(String jarSource, String jarTarget) throws BuildException {
         if (project.getJavaVersion().equals(Project.JAVA_1_1)) {
             throw new BuildException("The signjar task is only available on JDK versions 1.2 or greater");
-        } 
-
-        if (null == jar) {
-            throw new BuildException("jar attribute must be set");
-        } 
+        }
 
         if (null == alias) {
             throw new BuildException("alias attribute must be set");
-        } 
+        }
 
         if (null == storepass) {
             throw new BuildException("storepass attribute must be set");
-        } 
+        }
 
-        if(isUpToDate()) return;
+        if(isUpToDate(jarSource, jarTarget)) return;
 
         final StringBuffer sb = new StringBuffer();
 
         final ExecTask cmd = (ExecTask) project.createTask("exec");
         cmd.setExecutable("jarsigner");
-        
+
         if (null != keystore) {
             cmd.createArg().setValue("-keystore");
             cmd.createArg().setValue(keystore);
-        } 
+        }
 
         if (null != storepass) {
             cmd.createArg().setValue("-storepass");
             cmd.createArg().setValue(storepass);
-        } 
+        }
 
         if (null != storetype) {
             cmd.createArg().setValue("-storetype");
             cmd.createArg().setValue(storetype);
-        } 
+        }
 
         if (null != keypass) {
             cmd.createArg().setValue("-keypass");
             cmd.createArg().setValue(keypass);
-        } 
+        }
 
         if (null != sigfile) {
             cmd.createArg().setValue("-sigfile");
             cmd.createArg().setValue(sigfile);
-        } 
+        }
 
-        if (null != signedjar) {
+        if (null != jarTarget) {
             cmd.createArg().setValue("-signedjar");
-            cmd.createArg().setValue(signedjar);
-        } 
+            cmd.createArg().setValue(jarTarget);
+        }
 
         if (verbose) {
             cmd.createArg().setValue("-verbose");
-        } 
+        }
 
         if (internalsf) {
             cmd.createArg().setValue("-internalsf");
-        } 
+        }
 
         if (sectionsonly) {
             cmd.createArg().setValue("-sectionsonly");
-        } 
+        }
+
+        cmd.createArg().setValue(jarSource);
 
-        cmd.createArg().setValue(jar);
-        
 
         cmd.createArg().setValue(alias);
 
-        log("Signing Jar : " + (new File(jar)).getAbsolutePath());
+        log("Signing Jar : " + (new File(jarSource)).getAbsolutePath());
         cmd.setFailonerror(true);
         cmd.setTaskName( getTaskName() );
         cmd.execute();
     }
 
-    protected boolean isUpToDate() {
+    protected boolean isUpToDate(String jarSource, String jarTarget) {
+        if( null == jarSource ) {
+            return false;
+        }
+
+        if( null != jarTarget ) {
 
-        if( null != jar && null != signedjar ) {
+            final File jarFile = new File(jarSource);
+            final File signedjarFile = new File(jarTarget);
 
-            final File jarFile = new File(jar);
-            final File signedjarFile = new File(signedjar);
-            
             if(!jarFile.exists()) return false;
             if(!signedjarFile.exists()) return false;
             if(jarFile.equals(signedjarFile)) return false;
             if(signedjarFile.lastModified() > jarFile.lastModified())
                 return true;
+        } else {
+            if( lazy ) {
+                return isSigned(jarSource);
+            }
         }
 
         return false;
     }
+
+    protected boolean isSigned(String jarFilename) {
+        final String SIG_START = "META-INF/";
+        final String SIG_END = ".SF";
+
+        File file = new File(jarFilename);
+        if( !file.exists() ) {
+            return false;
+        }
+        ZipFile jarFile = null;
+        try {
+            jarFile = new ZipFile(file);
+            if(null == alias) {
+                Enumeration entries = jarFile.entries();
+                while(entries.hasMoreElements()) {
+                    String name =  ((ZipEntry)entries.nextElement()).getName();
+                    if(name.startsWith(SIG_START) && name.endsWith(SIG_END)) {
+                        return true;
+                    }
+                }
+                return false;
+            } else {
+                return jarFile.getEntry(SIG_START+alias.toUpperCase()+
+                                        SIG_END) != null;
+            }
+        } catch(IOException e) {
+            return false;
+        } finally {
+            if(jarFile != null) {
+                try {jarFile.close();} catch(IOException e) {}
+            }
+        }
+    }
+
 }