Actually the code is structured as in the first design. But I think it's not very readable..
The namespaces name are saying nothing of the responsability of each class
Is it really useful to split between DAO and BLO layer a so small architecture? There is almost no logic..
The logic / responsability of the BLO is not identifiable by the names of class / methods / namespace
What is UserType? The namespace is not grouping it with any other class..
Config class is a good name for me since it identifies a functionality. But It's the only class with a precise purpose specified by its name.
Get3rdPartyUrl and logging in (to that url) could all be put together in a same class, while InitializeConfigValue and ParseErrorMessage could be put into some other Help class.
Contacting a 3rdParty WS is reusable. Everything should inherit from just one interface also defining logging.
The WS which I contact will make a callback to my infrastructure. I could I recognize / trace the session between this two calls? From my infrastructure and back to my infrastructure?
I wait your comment and proposal!
EDIT
This is the result after the first refactoring. What do you think about?
I do not split beetwen DAO and BLO levels in small projects. I use QueryObject pattern and put all my queries into this objects. You can put simple logic (validation f.e.) into this queries.
The WS which I contact will make a callback to my infrastructure. I could I recognize / >trace the session between this two calls? From my infrastructure and back to my >infrastructure?
You can use WS-Addressing. WS-Addressing headers has fields wsa:MessageID and wsa:RelatesTo for message correlations (mean this as MessageId and CorrelationId) and wsa:ReplyTo/wsa:Address for callback server address.
For example Oracle SOA Suite has strong WS-Addressing support out-of-the-box.
Related
I am using Apache CXF (apache-cxf-2.5.0) to create Web Services using a bottom-up approach (Java first approach). I want to return some data/records (for example, username, email) from a database table. I can write a Java class which returns a simple response. But I am not able to find way to return a response such as data/records extracted from a database table. How to do that?
You don't mention how you are accessing the database, but the basic idea is that you ensure that the classes that you return have JAXB annotations (notably #XmlRootElement or #XmlType) on them, which allows CXF to convert the instances of those classes into XML document fragments. The classes which you annotate this way probably should not have lots of functionality in them; they should exist just to hold data. (I find anything else too confusing given the complex lifecycle they'll have.) Once the annotations are in place, just return the relevant objects and all the conversions will happen automatically.
I'm talking a simple class like this:
#XmlRootElement // <---- THIS LINE HERE!
public class UserInfo {
public String username;
public String email;
}
You can use this in conjunction with other annotations (e.g., for your ORM) as necessary. Of course, if you're talking straight JDBC to the DB to get the information out, you won't need to worry about that.
The one tricky bit is that the objects being returned will have a lifespan that goes beyond that of the database transaction you're using; you may need to detach (i.e., do some copying, though the ORM layer might provide assistance) the objects extracted from the DB for that to work. This won't be much of a concern in this case as the DB you're describing is very simple (one table, no inter-row relations) but could be an issue if you make things more complex.
Here is a description of the scenario and I would appreciate also any comments on the approach used
The core of my application is a set of web services backed by a P2P database. One service accepts a simple XML-based record (I have designed a generic schema for it). The service processes this data (mainly creating keys based on certain criteria) and pass the original data along with the created keys to a listening SocketServer in one of the listening P2P nodes. This key,data pair is routed to the proper node, which stores the data (associated with the key as an ID) in an XML database.
A second service accepts a query document that is structured based on the same schema, but with optional values that would be used for searching and matching from the previously stored ones. So the second service would pass this query (with the proper keys) to the P2P part, get back the results and pass them back to the service client.
E.g. if the original record submitted to the first service was < attr1 >value1 < /attr1 > < attr2 > value2 < / attr2 > (attribute list along with some other metadata mandated by the schema) then the second service should retrieve that record if the query received was < attr2 >value2 < / attr2 >
(I could later think about using more complex XPath or XQuery queries as the underlying XML database allows instead of exact matches for values here but that is not important at this stage. there is also a third service I am working on but it depends on getting the first two in proper shape first)
So my questions are:
1) What data type should I use as the parameters of the web services? How to utilize my schema for this usage? I was considering various XML binding frameworks (especially JAXB and SDO) for this but didn't know how to proceed.
2) How can I enhance the two services (call them store and search) to use dynamically created templates based on the original generic schema? The service would still accept documents of the main schema type but has the inner attribute list based on a template say template1 only requires whose values are ints while template2 require (float) and (string). The current JSP-based prototype manually creates this template but as an XML document that is assembled by hand (<>tags dispersed in text) and there is no type checking what so ever so I thought I could do better!
3) Is it possible to generate a quick web app prototype for simple access to this system (again by using the schema (&templates) to edit the appropriate XML message structures? What I am looking for is for the (human) user to choose a template and then just "fill in the blanks" and submit, no need for any fancy look and feel.
4) Can I or how can I also use this XML message type for communicating across sockets?
5) Does it matter if I deploy the services as stateless EJBs or not? Do I need them to be EJBs or servlets would be more than enough?
I currently have a rudimentary implementation (from previous developers) that were meant for a subset of my current requirements (I am improving on the services and adding new derived ones) but there was no schema nor validation and the data is passed all along as basic strings, thus providing weak typing and difficult to update manual parsing. The reason I want to update this to a stronger bound typing is to introduce changes in the data schema that would be passed along the whole system easily. Basically I want the system to be as less coupled to the data format/schema used as possible; the current prototype is too coupled to the data that I am finding it extremely difficult to change the data without breaking the system.
My initial investigation led me to consider JAXB but it supports only static typing (cannot create a schema/types dynamically at runtime that I want to persist for later usage). So I came across SDO which has both dynamic and static typing. The problem is just that there is not enough community and/or examples of using this approach so it seems risky (the examples of Apache Tuscany and Eclipselink implementations are very scarce and I could not find complete examples that are not 5+ years old (like this http://www.ibm.com/developerworks/java/library/j-sdo/) and also tackles the XML use case of SDO (most seem to focus on the relational usage of SDO).
This is my first time asking for programming help (here and elsewhere) so please bear with me. I searched a lot on the net but I could not find anything useful but pieces here and there that did not add up.
Any comment or hint is really appreciated.
trfndr
EDIT
I forgot one thing: how would the search service get back the results? Since it is opening a client socket connection, there is no way to get back any results synchronously. The current implementation tackles this by having the service client opening a listening socket on a random port and putting this contact info in the query document. After the search web service sends the query to the p2p part it finishes. The p2p sends the results as a WS call to another service which sends them back to the service client socket. I don't like this approach much, is there any more elegant solution?
I lead the EclipseLink JAXB & SDO implementations and represent Oracle on those specifications so hopefully I can help you out. This question is very similar to talk I'm giving at JavaOne in September.
1) What data type should I use as the
parameters of the web services? How to
utilize my schema for this usage? I
was considering various XML binding
frameworks (especially JAXB and SDO)
for this but didn't know how to
proceed.
This depend's on what web service framework you are using. JAXB is much easier to use with JAX-WS, and while JAXB is still easier to use with JAX-RS SDO, is a possible alternative.
2) How can I enhance the two services
(call them store and search) to use
dynamically created templates based on
the original generic schema? The
service would still accept documents
of the main schema type but has the
inner attribute list based on a
template say template1 only requires
whose values are ints while template2
require (float) and (string). The
current JSP-based prototype manually
creates this template but as an XML
document that is assembled by hand
(<>tags dispersed in text) and there
is no type checking what so ever so I
thought I could do better!
I'm not 100% what you mean here, but the following may be helpful:
Using #XmlAnyElement to Build a Generic Message
3) Is it possible to generate a quick
web app prototype for simple access to
this system (again by using the schema
(&templates) to edit the appropriate
XML message structures? What I am
looking for is for the (human) user to
choose a template and then just "fill
in the blanks" and submit, no need for
any fancy look and feel.
JAX-RS is a nice framework for creating quick prototypes. Below is an example I created:
Part 1 - The Database
Part 2 - Mapping the Database to Objects
Part 3 - Mapping the Objects to XML
Part 4 - The RESTful Service
Part 5 - The Client
4) Can I or how can I also use this
XML message type for communicating
across sockets?
I prefer frameworks like JAX-RS that communicate over the HTTP protocol.
5) Does it matter if I deploy the
services as stateless EJBs or not? Do
I need them to be EJBs or servlets
would be more than enough?
My preference is to use an EJB session bean for the service. If you are interacting with a database then you can leverage the Java Transaction API (JTA) to manage your database transactions.
Part 4 - The RESTful Service
SDO
EclipseLink is the SDO 2.1.1 (JSR-235) reference implementation. We have some examples posted below. If you are looking how to do something specific, I will try to post a relevant example.
http://wiki.eclipse.org/EclipseLink/Examples/SDO
JAXB
JAXB is static. It is also more popular than SDO. Recognizing this in EclipseLink we have implemented a dynamic JAXB feature. It gives you the dynamic aspect of SDO with a JAXB slant.
http://wiki.eclipse.org/EclipseLink/Examples/MOXy/Dynamic
EDIT #1
Since you are dealing with JAX-WS and your model is almost entirely dynamic, I think you should skip the JAXB binding altogether. In the following link see the section "Switching Off Data Binding"
http://java.sun.com/developer/technicalArticles/xml/jaxrpcpatterns3/
This will give us the body of the message as a javax.xml.transform.Source object. We will need to process the XML based on the dynamic templates. SDO would be a good choice here. You can constantly add new types to the HelperContext using XML schemas.
helperContext.getXSDHelper().define(schema1, null);
helperContext.getXSDHelper().define(schema2, null);
You wil be able to unmarshal the Source from the web service as follows:
XMLDocument doc = helperContext.getXMLHelper().load(source, null, null);
DataObject rootDataObject = doc.getRootObject();
String someValue = rootDataObject.getString("attr3/childAttr/anotherChildAttr");
You will also be able to use the XMLHelper to marshal your objects to XML when calling another service.
We currently have an application that retrieves data from the server through a web service and populates a DataSet. Then the users of the API manipulate it through the objects which in turn change the dataset. The changes are then serialized, compressed and sent back to the server to get updated.
However, I have begin using NHibernate within projects and I really like the disconnected nature of the POCO objects. The problem we have now is that our objects are so tied to the internal DataSet that they cannot be used in many situations and we end up making duplicate POCO objects to pass back and forth.
Batch.GetBatch() -> calls to web server and populates an internal dataset
Batch.SaveBatch() -> send changes to web server from dataset
Is there a way to achieve a similar model that we are using which all database access occurs through a web service but use NHibernate?
Edit 1
I have a partial solution that is working and persisting through a web service but it has two problems.
I have to serialize and send my whole collection and not just changed items
If I try to repopulate the collection upon return my objects then any references I had are lost.
Here is my example solution.
Client Side
public IList<Job> GetAll()
{
return coreWebService
.GetJobs()
.BinaryDeserialize<IList<Job>>();
}
public IList<Job> Save(IList<Job> Jobs)
{
return coreWebService
.Save(Jobs.BinarySerialize())
.BinaryDeserialize<IList<Job>>();
}
Server Side
[WebMethod]
public byte[] GetJobs()
{
using (ISession session = NHibernateHelper.OpenSession())
{
return (from j in session.Linq<Job>()
select j).ToList().BinarySerialize();
}
}
[WebMethod]
public byte[] Save(byte[] JobBytes)
{
var Jobs = JobBytes.BinaryDeserialize<IList<Job>>();
using (ISession session = NHibernateHelper.OpenSession())
using (ITransaction transaction = session.BeginTransaction())
{
foreach (var job in Jobs)
{
session.SaveOrUpdate(job);
}
transaction.Commit();
}
return Jobs.BinarySerialize();
}
As you can see I am sending the whole collection to the server each time and then returning the whole collection. But I'm getting a replaced collection instead of a merged/updated collection. Not to mention the fact that it seems highly inefficient to send all the data back and forth when only part of it could be changed.
Edit 2
I have seen several references on the web for almost a transparent persistent mechanism. I'm not exactly sure if these will work and most of them look highly experimental.
ADO.NET Data Services w/NHibernate (Ayende)
ADO.NET Data Services w/NHibernate (Wildermuth)
Custom Lazy-loadable Business Collections with NHibernate
NHibernate and WCF is Not a Perfect Match
Spring.NET, NHibernate, WCF Services and Lazy Initialization
How to use NHibernate Lazy Initializing Proxies with Web Services or WCF
I'm having a hard time finding a replacement for the DataSet model we are using today. The reason I want to get away from that model is because it takes a lot of work to tie every property of every class to a row/cell of a dataset. Then it also tightly couples all of my classes together.
I've only taken a cursory look at your question, so forgive me if my response is shortsighted but here goes:
I don't think you can logically get away from doing a mapping from domain object to DTO.
By using the domain objects over the wire you are tightly coupling your client and service, part of the reason to have a service in the first place is to promote loose coupling. So that's an immediate issue.
On top of that you're going to end up with a brittle domain logic interface where you can't make changes on the service side without breaking your client.
I suspect your best bet would be to implement a loosely coupled service which implements a REST / or some other loosely coupled interface. You could use a product such as automapper to make the conversions simpler and easier and also flatten data structures as necessary.
At this point I don't know of any way to really cut down the verbosity involved in doing the interface layers but having worked on large projects that didn't make the effort I can honestly tell you the savings wasn't worth it.
I think your issue revolves around this issue:
http://thatextramile.be/blog/2010/05/why-you-shouldnt-expose-your-entities-through-your-services/
Are you or are you not going to send ORM-Entities over the wire?
Since you have a Services-Oriented architecture.. I (like the author) do not recommend this practice.
I use NHibernate. I call those ORM-Entities. They are THE POCO model. But they have "virtual" properties that allow for lazy-loading.
However, I also have some DTO-Objects. These are also POCO's. These do not have lazy'loading friendly properties.
So I do alot of "converting". I hydrate ORM-Entities (with NHibernate)...and then I end up converting them to Domain-DTO-Objects. Yes, it stinks in the beginning.
The server sends out the Domain-DTO-Objects's. There is NO lazy loading. I have to populate them with the "Goldie Locks" "just right" model. Aka, if I need Parent(s) with one level of children, I have to know that up front and send the Domain-DTO-Objects over that way, with just the right amount of hydration.
WHen I send back Domain-DTO-Objects's (from client to the server), I have to reverse the process. I convert the Domain-DTO-Objects into ORM-Entities. And allow NHibernate to work with the ORM-Entities.
Because the architecture is "disconnected", I do alot of (NHiberntae) ".Merge()" calls.
// ormItem is any NHibernate poco
using (ISession session = ISessionCreator.OpenSession())
{
using (ITransaction transaction = session.BeginTransaction())
{
session.BeginTransaction();
ParkingAreaNHEntity mergedItem = session.Merge(ormItem);
transaction.Commit();
}
}
.Merge is a wonderful thing. Entity Framework does not have it. Boo.
Is this alot of setup? Yes.
Do I think it is perfect? No.
However. Because I send very basic DTO's(Poco's) that are not "flavored" to the ORM, I have the ability to switch ORM's without killing my contracts to the outside world.
My datalayer can be ADO.NET, EF, NHibernate, or anything. I have to write the "Converters" if I switch, and the ORM code, but everything else is isolated.
Many people argue with me. They said I'm doing too much, and the ORM-Entities are fine.
Again, I like to "now allow any lazy loading" appearances. And I prefer to have my data-layer isolated. My clients should not know or care about my data-layer/orm of choice.
There are just enough subtle differences (or some not so subtle ones) between EF and NHibernate to screwball the game plan.
Do my Domain-DTO-Objects's look 95% like my ORM-Entities? Yep. But its the 5% that can screwball you.
Moving from DataSets, especially if they are populated from stored-procedures with alot of biz-logic in the TSQL, isn't trivial. But now that I do object model, and I NEVER write a stored procedure that isn't simple CRUD functions, I'd never go back.
And I hate maintenance projects with voodoo TSQL in the stored procedures. It ain't 1999 anymore. Well, most places.
Good luck.
PS Without .Merge(in EF), here is what you have to do in a disconnected world: (boo microsoft)
http://www.entityframeworktutorial.net/EntityFramework4.3/update-many-to-many-entity-using-dbcontext.aspx
I'm after some guidance on how to approach coding a problem, I don't want to jump straight into coding without think about it as I need it to be as generic and customisable as possible,
The scenario is i have a web service that acts as a gateway to downstream services, with the aim of authenticating and authorising SOAP message destined for down stream services, basically allivating the downstream service from doing it themselves. Each SOAP message has a variety of different WS-Security mechanisms attached usually a WS-UsernameToken, WS-Timestamp, and a XML Signature of the message body.
My problem is i want to figure out a good extensible way of validating all these security mechanims, I'm not after how to do it just how to appraoch it.
I thought about having a controller class that is intialised and controls the validation flow i.e.
ISecurityController controller = SecurityControllerFacotry.getInstance();
boolean proceed = controller.Validate(soapMessage);
using it very much like a template design pattern which ditates the flow of logic i.e.
public Boolean Validate(Message soapMessage)
{
return ValidateAuthentication(soapMessage) && ValidateTimeStamp(soapMessage) && ValidateSignture(soapMessage);
}
Would this be the best apporach to the problem?
Also would it be best to put these validation methods each into a class of there own that which implemented a common interface? So that a class could be instantiated and retrieved from some sort of validation factory i.e.
IValidationMechanism val = ValidationFactory.getValidationType(ValidationFactory.UsernameToken);
boolean result = val.Validate(soapMessage);
This would give me an an easily extensible aspect.
Would this be an vaible solution or can anyone think of other ways of doing it?
I'm interset in design patterns and good oo principles so would like to go down a route utilising them if possible.
Thanks in advance
Jon
EDIT: The service is basically a gateway security service that relieves the burden of authentication and authorisation from services that sit behind it. The security service can be thought of as an implicitly invoke intermediary on the SOAP message path that validates the security mechanisms in the SOAP message and depending on the validation result forwards the message to the appropriate down stream service by interrogating the WS-addressing headers. Although the service is not really the question it is more on how to implement the validation procedure.
I think your intuition on this is good; go with the single interface approach. That is, hide your validation implementations behind a single validation interface; this allows you to extend your validation implementations later without modifying the calling code.
And yes, the idea of putting the validation into its own class is a good one; you might want to think about having a common base class, if you have any common validation items (for example, username might be a common validation element, even though each different validation scheme may encode it differently; one as an element, another as an attribute, etc.). I think validation classes is a more appropriate mapping for the level of complexity that you're talking about anyhow, as opposed to validation methods; I suspect that the type of validation you're doing requires groups of methods (i.e., classes).
I can think of another way to validate your SOAP message against different validations. You use a visitor Pattern.
For that You will have a simple wrapper around the SOAP message you get.
MySoapMessage{
SOAPMessage soapMessage;
List<String> validatonErrors;
void accept(Validator validator){
validator.isValid(this);
}
}
Your security Controller will contain the list of Validatiors which you will inject basically.
SecurityController{
List<IValidator> validators;
//Validate the message
void validate(MySOAPMessage soapMessage){
forEach(Validator validator: validators){
soapMessage.isValid(validator)
}
}
}
Your Validators will look something like this.
UserNameValidator implements IValidator{
public void validate(MySOAPMessage message){
// Validate and put error if any
}
}
You dont need and unnecessary factory here for the validators.. if you want to want to add/remove validators from the controller you just inject/un inject then from the list.
Spring has a generic validation package that handles this type of process nicely IMHO.
Theirs looks something like
public interface Validator {
public boolean supports(Class<?> clazz);
public void validate(Object o, Errors errors);
}
Granted, they're using an Errors param to return validation issues in, which might or might not suit your goal.
When coding web services, how do you structure your return values? How do you handle error conditions (expected ones and unexpected ones)? If you are returning something simple like an int, do you just return it, or embed it in a more complex object? Do all of the web methods within one service return an instance of a single class, or do you create a custom return value class for each method?
I like the Request/Response object pattern, where you encapsulate your arguments into a single [Operation]Request class, which has simple public properties on it.
Something like AddCustomerRequest, which would return AddCustomerResponse.
The response can include information on the success/failure of the operation, any messages that might be used by the UI, possibly the ID of the customer that was added, for example.
Another good pattern is to make these all derive from a simple IMessage interface, where your general end-point is something like Process(params IMessage[] messages)... this way you can pass in multiple operations in the same web request.
+1 for Ben's answer.
In addition, I suggest considering that the generic response allow for multiple error/warning items, to allow the reply to be as comprehensive and actionable as possible. (Would you want to use a compiler that stopped after the first error message, or one that told you as much as possible?)
If you're using SOAP web services then SOAP faults are the standard way to return error details, where the fault messages can return whatever additional detail you like.
Soap faults are a standard practice where the calling application is a Soap client. There are cases, such as a COM client using XMLHTTP, where the Soap is parsed as XML and Soap faults cannot be easily handled. Can't vote yet but another +1 for #Ben Scheirman.