#1 Ocket.Text#write(text, type) added

src/main/java/com/jcabi/s3/Bucket.java

@@ -48,30 +48,31 @@ public interface Bucket {
      * Get region we're in.
      * @return Region
      */
-    @NotNull
+    @NotNull(message = "region is never NULL")
     Region region();
 
     /**
      * Get bucket name.
      * @return Bucket name
      */
-    @NotNull
+    @NotNull(message = "bucket name is never NULL")
     String name();
 
     /**
      * Get object.
      * @param key Name of it in the bucket
      * @return Ocket
      */
-    @NotNull
-    Ocket ocket(@NotNull String key);
+    @NotNull(message = "ocket is never NULL")
+    Ocket ocket(@NotNull(message = "S3 key can't be NULL") String key);
 
     /**
      * Delete object from bucket.
      * @param key Name of it in the bucket
      * @throws OcketNotFoundException If not found
      */
-    void remove(@NotNull String key) throws OcketNotFoundException;
+    void remove(@NotNull(message = "S3 key can't be NULL") String key)
+        throws OcketNotFoundException;
 
     /**
      * Prefixed.
@@ -94,7 +95,9 @@ final class Prefixed implements Bucket {
          * @param bucket Original bucket
          * @param pfx Prefix
          */
-        public Prefixed(final Bucket bucket, final String pfx) {
+        public Prefixed(
+            @NotNull(message = "bucket can't be NULL") final Bucket bucket,
+            @NotNull(message = "prefix can't be NULL") final String pfx) {
             this.origin = bucket;
             this.prefix = pfx;
         }

src/main/java/com/jcabi/s3/Ocket.java

@@ -122,13 +122,23 @@ public String read() throws IOException {
             return baos.toString(CharEncoding.UTF_8);
         }
         /**
-         * Read content as string.
+         * Write content as string.
          * @param text Text to write
          * @throws IOException If fails
          */
         public void write(@NotNull final String text) throws IOException {
+            this.write(text, "text/plain");
+        }
+        /**
+         * Write content as string, with a specified content type.
+         * @param text Text to write
+         * @param type Content type
+         * @throws IOException If fails
+         */
+        public void write(@NotNull final String text,
+            @NotNull final String type) throws IOException {
             final ObjectMetadata meta = new ObjectMetadata();
-            meta.setContentType("text/plain");
+            meta.setContentType(type);
             meta.setContentLength((long) text.getBytes(Charsets.UTF_8).length);
             meta.setContentEncoding(CharEncoding.UTF_8);
             this.origin.write(

src/main/java/com/jcabi/s3/Region.java

@@ -52,12 +52,14 @@ public interface Region {
      * @param name Name of the bucket to get
      * @return Bucket
      */
-    Bucket bucket(String name);
+    @NotNull(message = "bucket is never NULL")
+    Bucket bucket(@NotNull(message = "bucket name can't be NULL") String name);
 
     /**
      * Get a client.
      * @return Amazon S3
      */
+    @NotNull(message = "AWS client is never NULL")
     AmazonS3 aws();
 
     /**