Make lastInsertedId return null on failure.

Since we're rejiggering, we'll take this opportunity to eliminate the use of -1
as a sentinel id. Maybe your database id generator returns -1. Unlikely, but
not impossible.

src/main/java/com/samskivert/jdbc/BaseLiaison.java

@@ -38,18 +38,19 @@ public abstract class BaseLiaison implements DatabaseLiaison
 
     @Deprecated
     public int lastInsertedId (Connection conn, String table, String column) throws SQLException {
-        return lastInsertedId(conn, null, table, column);
+        Integer id = lastInsertedId(conn, null, table, column);
+        return (id == null) ? -1 : id;
     }
 
     // from DatabaseLiaison
-    public int lastInsertedId (Connection conn, Statement istmt, String table, String column)
+    public Integer lastInsertedId (Connection conn, Statement istmt, String table, String column)
         throws SQLException
     {
         // if this JDBC driver supports getGeneratedKeys, use it!
         if (istmt != null && conn.getMetaData().supportsGetGeneratedKeys()) {
             return istmt.getGeneratedKeys().getInt(column);
         }
-        return -1;
+        return null;
     }
 
     // from DatabaseLiaison

src/main/java/com/samskivert/jdbc/DatabaseLiaison.java

@@ -55,8 +55,9 @@ public interface DatabaseLiaison
      *
      * @param istmt the insert statement that generated the keys. May be null if the ORM doesn't
      * have the statement handy.
+     * @return the requested inserted id, or null if no last inserted id can be obtained.
      */
-    public int lastInsertedId (Connection conn, Statement istmt, String table, String column)
+    public Integer lastInsertedId (Connection conn, Statement istmt, String table, String column)
         throws SQLException;
 
     /**

src/main/java/com/samskivert/jdbc/HsqldbLiaison.java

@@ -73,11 +73,11 @@ public class HsqldbLiaison extends BaseLiaison
     }
 
     @Override // from DatabaseLiaison
-    public int lastInsertedId (Connection conn, Statement istmt, String table, String column)
+    public Integer lastInsertedId (Connection conn, Statement istmt, String table, String column)
         throws SQLException
     {
-        int id = super.lastInsertedId(conn, istmt, table, column);
-        if (id >= 0) return id;
+        Integer id = super.lastInsertedId(conn, istmt, table, column);
+        if (id != null) return id;
 
         // HSQL does not keep track of per-table-and-column insertion data, so we are pretty much
         // going on blind faith here that we're fetching the right ID. In the overwhelming number
@@ -86,7 +86,7 @@ public class HsqldbLiaison extends BaseLiaison
          try {
              stmt = conn.createStatement();
              ResultSet rs = stmt.executeQuery("call IDENTITY()");
-             return rs.next() ? rs.getInt(1) : -1;
+             return rs.next() ? rs.getInt(1) : null;
          } finally {
              JDBCUtil.close(stmt);
          }

src/main/java/com/samskivert/jdbc/MySQLLiaison.java

@@ -50,14 +50,14 @@ public class MySQLLiaison extends BaseLiaison
     }
 
     @Override // from DatabaseLiaison
-    public int lastInsertedId (Connection conn, Statement istmt, String table, String column)
+    public Integer lastInsertedId (Connection conn, Statement istmt, String table, String column)
         throws SQLException
     {
         // MySQL hackily reports the last inserted key as GENERATED_KEY, so we call super with that
         // "column name"; but if that doesn't work (we're using an old JDBC driver without support
         // for returning generated keys), fall back to the old old method
-        int id = super.lastInsertedId(conn, istmt, table, "GENERATED_KEY");
-        if (id >= 0) return id;
+        Integer id = super.lastInsertedId(conn, istmt, table, "GENERATED_KEY");
+        if (id != null) return id;
 
         // MySQL does not keep track of per-table-and-column insertion data, so we are pretty much
         // going on blind faith here that we're fetching the right ID. In the overwhelming number
@@ -66,7 +66,7 @@ public class MySQLLiaison extends BaseLiaison
         try {
             stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery("select LAST_INSERT_ID()");
-            return rs.next() ? rs.getInt(1) : -1;
+            return rs.next() ? rs.getInt(1) : null;
         } finally {
             JDBCUtil.close(stmt);
         }

src/main/java/com/samskivert/jdbc/PostgreSQLLiaison.java

@@ -35,12 +35,12 @@ public class PostgreSQLLiaison extends BaseLiaison
     }
 
     // from DatabaseLiaison
-    public int lastInsertedId (Connection conn, Statement istmt, String table, String column)
+    public Integer lastInsertedId (Connection conn, Statement istmt, String table, String column)
         throws SQLException
     {
         // try the default first, which uses JDBC's getGeneratedKeys mechanism
-        int id = super.lastInsertedId(conn, istmt, table, column);
-        if (id >= 0) return id;
+        Integer id = super.lastInsertedId(conn, istmt, table, column);
+        if (id != null) return id;
 
         // PostgreSQL's support for auto-generated ID's comes in the form of appropriately named
         // sequences and DEFAULT nextval(sequence) modifiers in the ID columns. To get the next ID,
@@ -50,7 +50,7 @@ public class PostgreSQLLiaison extends BaseLiaison
         try {
             ResultSet rs = stmt.executeQuery(
                 "select currval('\"" + table + "_" + column + "_seq\"')");
-            return rs.next() ? rs.getInt(1) :-1;
+            return rs.next() ? rs.getInt(1) : null;
         } finally {
             JDBCUtil.close(stmt);
         }