Skipping of unchanged scenarios is now based on MD5-sums of all classes

When working with Netbeans, the schema was often rebuild without need.
The cause of this behaviour was, that Netbeans (or Maven itself) sometimes
touches unchanged classes. To avoid this, hibernat4-maven-plugin now
calculates MD5-sums for all annotated classes and compares these instead of
the last-modified value.

diff --git a/src/main/java/de/juplo/plugins/hibernate4/Hbm2DdlMojo.java b/src/main/java/de/juplo/plugins/hibernate4/Hbm2DdlMojo.java
index 8db0fd6..c9d5013 100644 (file)
--- a/src/main/java/de/juplo/plugins/hibernate4/Hbm2DdlMojo.java
+++ b/src/main/java/de/juplo/plugins/hibernate4/Hbm2DdlMojo.java
@@ -21,10 +21,13 @@ import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
+import java.io.InputStream;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
+import java.math.BigInteger;
 import java.net.URL;
 import java.net.URLClassLoader;
+import java.security.MessageDigest;
 import java.sql.Connection;
 import java.sql.Driver;
 import java.sql.DriverManager;
@@ -73,7 +76,7 @@ public class Hbm2DdlMojo extends AbstractMojo
   public final static String PASSWORD = "hibernate.connection.password";
   public final static String DIALECT = "hibernate.dialect";
 
-  private final static String TIMESTAMPS = "schema.timestamp";
+  private final static String MD5S = "schema.md5s";
 
   /**
    * The project whose project files to create.
@@ -202,9 +205,9 @@ public class Hbm2DdlMojo extends AbstractMojo
     if (!dir.exists())
       throw new MojoExecutionException("Cannot scan for annotated classes in " + outputDirectory + ": directory does not exist!");
 
-    Map<String,Long> timestamps;
+    Map<String,String> md5s;
     boolean modified = false;
-    File saved = new File(outputDirectory + File.separator + TIMESTAMPS);
+    File saved = new File(outputDirectory + File.separator + MD5S);
 
     if (saved.exists())
     {
@@ -212,18 +215,18 @@ public class Hbm2DdlMojo extends AbstractMojo
       {
         FileInputStream fis = new FileInputStream(saved);
         ObjectInputStream ois = new ObjectInputStream(fis);
-        timestamps = (HashMap<String,Long>)ois.readObject();
+        md5s = (HashMap<String,String>)ois.readObject();
         ois.close();
       }
       catch (Exception e)
       {
-        timestamps = new HashMap<String,Long>();
+        md5s = new HashMap<String,String>();
         getLog().warn("Cannot read timestamps from saved: " + e);
       }
     }
     else
     {
-      timestamps = new HashMap<String,Long>();
+      md5s = new HashMap<String,String>();
       try
       {
         saved.createNewFile();
@@ -279,19 +282,32 @@ public class Hbm2DdlMojo extends AbstractMojo
       if (db.getAnnotationIndex().containsKey(Embeddable.class.getName()))
         classNames.addAll(db.getAnnotationIndex().get(Embeddable.class.getName()));
 
+      MessageDigest digest = java.security.MessageDigest.getInstance("MD5");
       for (String name : classNames)
       {
         Class<?> annotatedClass = classLoader.loadClass(name);
         classes.add(annotatedClass);
-        URL classUrl = annotatedClass.getResource(annotatedClass.getSimpleName() + ".class");
-        File classFile = new File(classUrl.toURI());
-        long lastModified = classFile.lastModified();
-        long timestamp = !timestamps.containsKey(name) ? 0 : timestamps.get(name);
-        if (lastModified > timestamp)
+        InputStream is =
+            annotatedClass
+                .getResourceAsStream(annotatedClass.getSimpleName() + ".class");
+        byte[] buffer = new byte[1024*4]; // copy data in 4MB-chunks
+        int i;
+        while((i = is.read(buffer)) > -1)
+          digest.update(buffer, 0, i);
+        is.close();
+        byte[] bytes = digest.digest();
+        BigInteger bi = new BigInteger(1, bytes);
+        String newMd5 = String.format("%0" + (bytes.length << 1) + "x", bi);
+        String oldMd5 = !md5s.containsKey(name) ? "" : md5s.get(name);
+        if (!newMd5.equals(oldMd5))
         {
           getLog().debug("Found new or modified annotated class: " + name);
           modified = true;
-          timestamps.put(name, lastModified);
+          md5s.put(name, newMd5);
+        }
+        else
+        {
+          getLog().debug(oldMd5 + " -> class unchanged: " + name);
         }
       }
     }
@@ -549,7 +565,7 @@ public class Hbm2DdlMojo extends AbstractMojo
     {
       FileOutputStream fos = new FileOutputStream(saved);
       ObjectOutputStream oos = new ObjectOutputStream(fos);
-      oos.writeObject(timestamps);
+      oos.writeObject(md5s);
       oos.close();
       fos.close();
     }