Closes some unclosed streams

Some StringWriter streams were not closes in the examples. This commit
fixes this error.

pom.xml

@@ -7,7 +7,7 @@
 
 	<groupId>es.uvigo.esei.dai</groupId>
 	<artifactId>xml</artifactId>
-	<version>1.0.0</version>
+	<version>1.0.1</version>
 
 	<name>Ejemplos de DAI - APIs XML</name>
 	<inceptionYear>2014</inceptionYear>

src/main/java/es/uvigo/esei/dai/xml/dom/DOMParsing.java

@@ -102,7 +102,7 @@ public class DOMParsing {
     return builder.parse(new File(documentPath));
   }
 
-  public static String toXML(Document document) throws TransformerException {
+  public static String toXML(Document document) throws TransformerException, IOException {
     // Creación y configuración del transformador. En este caso, se activa
     // la indentación del XML
     final TransformerFactory factory = TransformerFactory.newInstance();
@@ -112,10 +112,10 @@ public class DOMParsing {
     transformer.setOutputProperty(OutputKeys.INDENT, "yes");
 
     // El resultado se almacenará en una cadena de texto
-    final StringWriter writer = new StringWriter();
-
-    transformer.transform(new DOMSource(document), new StreamResult(writer));
-
-    return writer.toString();
+    try (final StringWriter writer = new StringWriter()) {
+      transformer.transform(new DOMSource(document), new StreamResult(writer));
+  
+      return writer.toString();
+    }
   }
 }

src/main/java/es/uvigo/esei/dai/xml/xpath/XSLUtils.java

 package es.uvigo.esei.dai.xml.xpath;
 
 import java.io.File;
+import java.io.IOException;
 import java.io.StringWriter;
 
 import javax.xml.namespace.NamespaceContext;
@@ -76,14 +77,25 @@ public class XSLUtils {
     transformer.transform(xmlSource, result);
   }
 
-  public static String transformWithXSLT(File xml, File xslt) throws TransformerException {
+  public static String transformWithXSLT(File xml, File xslt) throws TransformerException, IOException {
     final TransformerFactory tFactory = TransformerFactory.newInstance();
     final Transformer transformer = tFactory.newTransformer(new StreamSource(xslt));
 
-    final StringWriter writer = new StringWriter();
+    try (final StringWriter writer = new StringWriter()) {
+      transformer.transform(new StreamSource(xml), new StreamResult(writer));
 
-    transformer.transform(new StreamSource(xml), new StreamResult(writer));
+      return writer.toString();
+    }
+  }
+
+  public static String transformToString(File xml) throws TransformerException, IOException {
+    final TransformerFactory tFactory = TransformerFactory.newInstance();
+    final Transformer transformer = tFactory.newTransformer();
+
+    try (final StringWriter writer = new StringWriter()) {
+      transformer.transform(new StreamSource(xml), new StreamResult(writer));
 
-    return writer.toString();
+      return writer.toString();
+    }
   }
 }