![]() SOAP with Attachments: Works but flawed design ![]() We need something that is both more efficient and standardized. It may be a solution, but it is both inefficient and non-standard. One could imagine that if Base 64 encoding was part of the SOAP standard, then there would be some standard way to indicate this SOAP message processors. In addition, the parser on the other side needs to know about the encoding so that it can decode the payload. Base 64 encoded binary winds up being, on average, 37% larger (number of bytes) than the raw, non-encoded binary data. So there, problem solved, right? Yes, but … it's a rather inefficient solution. Every byte gets mapped to these characters, so there's no way for any byte to get misinterpreted as anything that would choke an XML parser. It involves using a 64 character “alphabet” consisting of the lower case characters, a-z, the upper case characters, A-Z, the numbers 0-9, and the + and / symbols. This technique has been around (as a standard) since the 80's. One common way to do this is to use Base 64 encoding. There is a solution to this variant of our problem. We need a way to make sure those bytes aren't interpreted at all.īase 64 encoding: Works but bloated SOAP attachments That would cause any parser to think that the CDATA section had ended and the subsequent characters would be interpreted just like in our first attempt. It might seem unlikely, but our binary data could have just such a byte sequence in the middle of it. It does this by looking for the byte sequence corresponding to the characters ]]>. However, the parser has to figure out where the CDATA section ends. Now if we have bytes that would be interpreted as a > (for example,) they will be ignored. This modified approach might look like Listing 2. What about using a CDATA block? That will tell the parser to ignore the characters inside the block. So this approach will not work.īut wait, maybe there's a way to fix this approach. Any such byte sequence in text node above will cause the parser on the other side to break. So our binary data could easily have characters that correspond to reserved XML characters, like or &. An XML parser, whether it's a DOM, SAX, or StAX parser, must use the character set encoding of the document to interpret all the bytes in the document as characters. Remember that characters are also bytes, just like binary data. One way you might try is to simply dump the binary into a text node. Naive approaches to sending attachments with SOAP You see web pages do this all the time it can't be that hard, right? Let's explore some solutions to this problem. You just need a way to combine it with binary data. So should you just give up on sending attachments with SOAPall together? Of course not, there are too many advantages to SOAP. You'd like to use SOAP attachments, but it's limited to text. Ok, so you need to send binary data between applications. This poses a problem when your message format is text.Ĭombining binary data with SOAP attachments For example, let's say your message needs to include an image. This not only makes for large messages, but makes it incompatible with binary data. ![]() One of the main criticisms of SOAP is its use of XML, and that complaint often carries over when it comes to sending attachments with SOAP. SOAP standardizes the protocol (HTTP) and the data format (XML.) Standardization around SOAP has taken away a lot of the guesswork in sending data between systems. There are numerous protocols and data formats. ![]() There are endless ways to send data over the network, which means there are also many ways to send attachments with SOAP. In fact, reading through these articles on modern SOAP and RESTful web service development, it's amazing to see just how far software development in Java has come. I highly recommend these articles as a compliment to this slightly older tutorial. A step-by-step RESTful web services example with Spring Boot.The RESTful APIs tutorial: The ins and outs of effective RESTful web services.The simple bottom-up web service approach to creating SOAP based SOA components.How to build SOAP components using WSDL and a top-down web services approach.Modern SOAP web services development in Java with Eclipse.Looking for a more modern approach to web service development? Here are some of the latest REST tutorials and SOAP web services examples that we’ve published on TheServerSide. ![]()
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