fix: interpretation of empty but set "ssl" connection property

Commit a6a61be ignored the case that
the "ssl" property is set but empty, which means "true" according to
the documentation.
The consequence is that no SSL connection is attempted in this case.

closes #528, closes #529

pgjdbc/src/main/java/org/postgresql/core/v2/ConnectionFactoryImpl.java

@@ -61,7 +61,8 @@ public ProtocolConnection openConnectionImpl(HostSpec[] hostSpecs, String user,
     boolean trySSL;
     String sslmode = PGProperty.SSL_MODE.get(info);
     if (sslmode == null) { // Fall back to the ssl property
-      requireSSL = trySSL = PGProperty.SSL.getBoolean(info);
+      // assume "true" if the property is set but empty
+      requireSSL = trySSL = PGProperty.SSL.getBoolean(info) || "".equals(PGProperty.SSL.get(info));
     } else {
       if ("disable".equals(sslmode)) {
         requireSSL = trySSL = false;

pgjdbc/src/main/java/org/postgresql/core/v3/ConnectionFactoryImpl.java

@@ -76,7 +76,8 @@ public ProtocolConnection openConnectionImpl(HostSpec[] hostSpecs, String user,
     boolean trySSL;
     String sslmode = PGProperty.SSL_MODE.get(info);
     if (sslmode == null) { // Fall back to the ssl property
-      requireSSL = trySSL = PGProperty.SSL.getBoolean(info);
+      // assume "true" if the property is set but empty
+      requireSSL = trySSL = PGProperty.SSL.getBoolean(info) || "".equals(PGProperty.SSL.get(info));
     } else {
       if ("disable".equals(sslmode)) {
         requireSSL = trySSL = false;

pgjdbc/src/main/java/org/postgresql/ds/common/BaseDataSource.java

@@ -453,7 +453,7 @@ public void setSsl(boolean enabled) {
     if (enabled) {
       PGProperty.SSL.set(properties, true);
     } else {
-      PGProperty.SSL.set(properties, null);
+      PGProperty.SSL.set(properties, false);
     }
   }
 
@@ -462,7 +462,8 @@ public void setSsl(boolean enabled) {
    * @see PGProperty#SSL
    */
   public boolean getSsl() {
-    return PGProperty.SSL.isPresent(properties);
+    // "true" if "ssl" is set but empty
+    return PGProperty.SSL.getBoolean(properties) || "".equals(PGProperty.SSL.get(properties));
   }
 
   /**