Ensuring an unmarshalled InputStream is not closed

Accepting an existing InputStream for consuming, should not assume that
the InputStream can be closed.

Author: runeflobakk

jaxb/src/main/java/no/digipost/signature/jaxb/JaxbMarshaller.java

@@ -18,9 +18,9 @@
 import no.digipost.signature.xsd.SignatureApiSchemas;
 import no.digipost.xml.bind.MarshallingCustomization;
 import no.digipost.xml.parsers.SaxParserProvider;
+import no.digipost.xml.transform.sax.SaxInputSources;
 import org.w3c.dom.Document;
 import org.w3c.dom.Node;
-import org.xml.sax.InputSource;
 
 import javax.xml.bind.JAXBContext;
 import javax.xml.bind.Marshaller;
@@ -194,7 +194,7 @@ private <T> void doWithMarshaller(T object, ThrowingBiConsumer<? super T, ? supe
     }
 
     public <T> T unmarshal(InputStream inputStream, Class<T> type) {
-        Source xmlSource = saxParserProvider.createSource(new InputSource(inputStream));
+        Source xmlSource = saxParserProvider.createSource(SaxInputSources.fromInputStreamPreventClose(inputStream));
         return unmarshal(unmarshaller -> unmarshaller.unmarshal(xmlSource), type);
     }
 

jaxb/src/main/java/no/digipost/xml/transform/sax/ClosePreventingInputSource.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) Posten Norge AS
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package no.digipost.xml.transform.sax;
+
+import org.xml.sax.InputSource;
+
+import java.io.FilterInputStream;
+import java.io.InputStream;
+import java.io.Reader;
+import java.nio.charset.Charset;
+
+
+class ClosePreventingInputSource extends InputSource {
+
+    private boolean initialized;
+
+    public ClosePreventingInputSource(InputStream inputStream, Charset encoding) {
+        super(new ClosePreventingInputStream(inputStream));
+        if (encoding != null) {
+            this.setEncoding(encoding.name());
+        }
+        this.initialized = true;
+    }
+
+    private static final class ClosePreventingInputStream extends FilterInputStream {
+        public ClosePreventingInputStream(InputStream in) {
+            super(in);
+        }
+        @Override
+        public void close() {
+            // prevent closing
+        }
+    }
+
+
+
+    @Override
+    public final Reader getCharacterStream() {
+        return null;
+    }
+
+    @Override
+    public final void setCharacterStream(Reader characterStream) {
+        throw new UnsupportedOperationException("Setting a character stream is not supported");
+    }
+
+    @Override
+    public final void setByteStream(InputStream byteStream) {
+        if (initialized) {
+            throw new UnsupportedOperationException("Setting a byte stream is not supported");
+        }
+        super.setByteStream(byteStream);
+    }
+}

jaxb/src/main/java/no/digipost/xml/transform/sax/SaxInputSources.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) Posten Norge AS
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package no.digipost.xml.transform.sax;
+
+import org.xml.sax.InputSource;
+
+import java.io.InputStream;
+import java.net.URL;
+import java.nio.charset.Charset;
+
+import static java.util.Objects.requireNonNull;
+
+public final class SaxInputSources {
+
+    /**
+     * Create a SAX {@link InputSource} wrapping the given existing InputStream
+     * which will not be closed by anything consuming the InputSource.
+     * The wrapped InputStream, which will be returned by {@link InputSource#getByteStream()},
+     * will be ensured cannot be closed, even if attempted. The responsibility to
+     * properly manage an existing InputStream (i.e. closing)
+     * is outside the InputSource, and it cannot assume that the wrapped stream
+     * can be closed after done consuming it.
+     */
+    public static InputSource fromInputStreamPreventClose(InputStream inputStream) {
+        return fromInputStreamPreventClose(inputStream, null);
+    }
+
+    /**
+     * Create a SAX {@link InputSource} wrapping the given existing InputStream
+     * which will not be closed by anything consuming the InputSource.
+     *
+     * @see #fromInputStreamPreventClose(InputStream)
+     */
+    public static InputSource fromInputStreamPreventClose(InputStream inputStream, Charset encoding) {
+        return new ClosePreventingInputSource(inputStream, encoding);
+    }
+
+
+    public static InputSource fromClasspath(String resourceName) {
+        return fromClasspath(resourceName, null);
+    }
+
+    public static InputSource fromClasspath(String resourceName, Charset encoding) {
+        return fromClasspath(resourceName, encoding, UrlInputSource.class.getClassLoader());
+    }
+
+    public static InputSource fromClasspath(String resourceName, Charset encoding, ClassLoader classLoader) {
+        URL location = classLoader.getResource(resourceName.startsWith("/") ? resourceName.substring(1) : resourceName);
+        requireNonNull(location, resourceName + " not found on classpath");
+        return new UrlInputSource(location, encoding);
+    }
+
+    private SaxInputSources() {
+    }
+}

jaxb/src/main/java/no/digipost/xml/transform/sax/UrlInputSource.java

@@ -26,24 +26,18 @@
 
 import static java.util.Objects.requireNonNull;
 
-public class UrlInputSource extends InputSource {
+class UrlInputSource extends InputSource {
 
-    public static UrlInputSource fromClasspath(String resourceName, Charset encoding) {
-        return fromClasspath(resourceName, encoding, UrlInputSource.class.getClassLoader());
-    }
-
-    public static UrlInputSource fromClasspath(String resourceName, Charset encoding, ClassLoader classLoader) {
-        URL location = classLoader.getResource(resourceName.startsWith("/") ? resourceName.substring(1) : resourceName);
-        requireNonNull(location, resourceName + " not found on classpath");
-        return new UrlInputSource(location, encoding);
-    }
-
-    private URL location;
+    private final URL location;
+    private boolean initialized;
 
     public UrlInputSource(URL location, Charset encoding) {
-        this.location = location;
-        this.setEncoding(encoding.name());
+        this.location = requireNonNull(location, "location URL");
         this.setSystemId(location.toString());
+        if (encoding != null) {
+            this.setEncoding(encoding.name());
+        }
+        this.initialized = true;
     }
 
     @Override
@@ -58,13 +52,20 @@ public final InputStream getByteStream() {
     }
 
     @Override
-    public final String getEncoding() {
-        return super.getEncoding();
+    public final Reader getCharacterStream() {
+        return null;
     }
 
     @Override
-    public final Reader getCharacterStream() {
-        return null;
+    public final void setCharacterStream(Reader characterStream) {
+        throw new UnsupportedOperationException("Setting a character stream is not supported");
     }
 
+    @Override
+    public final void setByteStream(InputStream byteStream) {
+        if (initialized) {
+            throw new UnsupportedOperationException("Setting a byte stream is not supported");
+        }
+        super.setByteStream(byteStream);
+    }
 }

jaxb/src/main/java/no/digipost/xml/validation/SchemaHelper.java

@@ -16,7 +16,7 @@
 package no.digipost.xml.validation;
 
 import no.digipost.xml.parsers.SaxParserProvider;
-import no.digipost.xml.transform.sax.UrlInputSource;
+import no.digipost.xml.transform.sax.SaxInputSources;
 
 import javax.xml.XMLConstants;
 import javax.xml.transform.Source;
@@ -25,8 +25,6 @@
 
 import java.util.Collection;
 
-import static java.nio.charset.StandardCharsets.UTF_8;
-
 public final class SchemaHelper {
 
     public static Schema createW3cXmlSchema(Collection<String> schemaResourceNames) {
@@ -35,7 +33,7 @@ public static Schema createW3cXmlSchema(Collection<String> schemaResourceNames)
         }
         try {
             Source[] schemaSources = schemaResourceNames.stream()
-                    .map(resourceName -> UrlInputSource.fromClasspath(resourceName, UTF_8))
+                    .map(SaxInputSources::fromClasspath)
                     .map(SaxParserProvider.createSecuredProvider()::createSource)
                     .toArray(Source[]::new);