Added MailToStringTransformer.

org.springframework.integration.mail/src/main/java/org/springframework/integration/mail/transformer/MailToStringTransformer.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2002-2008 the original author or authors.
+ *
+ * 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 org.springframework.integration.mail.transformer;
+
+import java.io.ByteArrayOutputStream;
+import java.nio.charset.Charset;
+
+import javax.mail.Multipart;
+
+import org.springframework.integration.message.MessageBuilder;
+import org.springframework.util.Assert;
+
+/**
+ * Transforms a Message payload of type {@link javax.mail.Message} to a String.
+ * If the mail message's content is a String, it will be the payload of the
+ * result Message. If the content is a Multipart, a String will be created from
+ * an output stream of bytes using the provided charset (or UTF-8 by default).
+ * 
+ * @author Mark Fisher
+ */
+public class MailToStringTransformer extends AbstractMailMessageTransformer<String> {
+
+	private volatile String charset = "UTF-8";
+
+
+	/**
+	 * Specify the name of the Charset to use when converting from bytes.
+	 * The default is UTF-8.
+	 */
+	public void setCharset(String charset) {
+		Assert.notNull(charset, "charset must not be null");
+		Assert.isTrue(Charset.isSupported(charset), "unsupported charset '" + charset + "'");
+		this.charset = charset;
+	}
+
+	@Override
+	protected MessageBuilder<String> doTransform(javax.mail.Message mailMessage) throws Exception {
+		Object content = mailMessage.getContent();
+		if (content instanceof String) {
+			return MessageBuilder.withPayload((String) content);
+		}
+		if (content instanceof Multipart) {
+			ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+			((Multipart) content).writeTo(outputStream);
+			return MessageBuilder.withPayload(
+					new String(outputStream.toByteArray(), this.charset));
+		}
+		throw new IllegalArgumentException("failed to transform contentType ["
+				+ mailMessage.getContentType() +"] to String.");
+	}
+
+}