Spring Web Services 2 Cookbook Review

Introduction

Today, I will digress from my usual tutorials and guide format. Instead, I will provide a review of the Spring Web Services 2 Cookbook published by Packt. For the impatient, get the book! You won't regret it.

What is Spring Web Services 2 Cookbook?

Spring Web Services is a product of the Spring community focused on creating document-driven Web services.

Spring Web Services aims to facilitate contract-first SOAP service development, allowing for the creation of flexible web services using one of the many ways to manipulate XML payloads.

This comprehensive guide -- which provides professional expertise on a variety of technical topics right from setting-up a contract-first Web-Service, creating client of a Web-Service to serialization, monitoring, testing and security using Spring-WS -- helps you enhance your skills in Spring Web Services.

Spring Web Services 2 Cookbook includes a wide variety of recipes that covers most important topics used in real-world applications. It is a well-rounded guide covering a lot of ground in the Spring Web Services domain using systematic arranged chapters and focused recipes.

Source: Spring Web Services 2 Cookbook

The Good

The Spring Web-Services Cookbook 2 is an excellent resource for any developer who wants to incorporate Spring web service support in their projects. It covers everything from setting a simple web service provider to a highly secured, asynchronous web services leveraging various transports such as XMPP, JMS, and email (besides plain vanilla HTTP).

This book is also an outstanding reference for anyone who aspires to master the Spring web service. It discusses contract-first and contract-last development using actual samples, testing support with TCPMon and soapUI, handling and providing custom exceptions.

I'm surprised by the book's intensive coverage on marshalling. It even includes steps for MooseXML. What's even better with this book is it goes beyond simple and complex SOAP-based web services. Instead, the book also tackles topics on how to setup REST-based web services and other remoting technologies, i.e. RMI and Hessian.

The book has provided ample code samples with dependencies listed. If you're not a Maven user, you'll at least have an idea of what's needed. But to fully utilize the samples you must know Maven at least (if you're an avid Spring developer, this shouldn't be a problem)

The Bad

However, I do have some pointers that should have been included in the book (I know this is a cookbook).

1. I think the book should have some basic introduction regarding web services and how SOAP or REST helps us solve our problem.
2. The book should provide a section for newbies that demonstrates step-by-step, probably in graphical detail, on how to setup a basic web service. When reading the book, an interesting question keeps lingering on my mind: "How is a newbie supposed to understand this book without some basic experience with web services?" Maybe this is where the Spring documentation plays in?
3. There were a couple of glaring misspellings in the initial chapters. It's somewhat distracting and somewhat's gives me the feeling if the book was rushed. One term that keeps bothering me is the usage of "web-services" versus "web services". Somehow in the book they used both terms to denote the same thing.

The Comparison

As a guide writer, I also have written tutorials for Spring WS (web service). I admit the book has more technical detail with wider coverage. But the parts that I have written provides more step-by-step information especially for newcomers. But if you want to go beyond what I have shared on this blog, you must read this definitive cookbook.

Conclusion

Spring Web Services 2 Cookbook is a must-have cookbook for those who want to know more about Spring Web Services. You can find more information about this book by visiting the following link: http://www.packtpub.com/spring-web-services-cookbook/book

I hope you've been enlightened with this review. Don't forget to check my tutorials at the Tutorials section for more information on Spring WS.

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Spring MVC 3.1 - Implement CRUD with Spring Data Neo4j (Part 1)

Introduction

In this tutorial, we will create a simple CRUD application using Spring 3.1 and Neo4j. We will based this tutorial on a previous guide for MongoDB. This means we will re-use our existing design and implement only the data layer to use Neo4j as our data store.

Table of Contents

Part 1: Introduction and Functional Specs
Part 2: Java classes
Part 3: XML configuration
Part 4: HTML (with AJAX)
Part 5: Running the Application

Dependencies

• Spring core 3.1.0.RELEASE
• Spring Data Neo4j 2.1.0.M1
• Neo4j Kernel 1.6
• Neo4j Cypher 1.6
• Neo4j Cypher DSL 1.6
• See pom.xml for details

Github
To access the source code, please visit the project's Github repository (click here)

Functional Specs

Before we start, let's define our application's specification as follows:

• A CRUD page for managing users
• Use AJAX to avoid page refresh
• Users have roles: either admin or regular (default)
• Everyone can create new users and edit existing ones
• When editing, users can only edit first name, last name, and role fields
• A username is assumed to be unique

Here's our Use Case diagram:

[User]-(View)
[User]-(Add) 
[User]-(Edit) 
[User]-(Delete) 

Database

If you're new to Neo4j and Spring Data Neo4j and coming from a SQL-background, please take some time to read the following references:

• Neo4j Docs
• Good Relationships - The Spring Data Neo4j Guide Book
• Spring Date Neo4j Reference Card

In its simplest form, Neo4j is a NoSQL graph database containing nodes and relationships.

What is Neo4j?

The Neo4j data model consists of nodes and relationships, both of which can have key/value-style properties. What does that mean, exactly? Nodes are the graph database name for records, with property keys instead of column names. That's normal enough. Relationships are the special part. In Neo4j, relationships are first-class citizens, meaning they are more than a simple foreign-key reference to another record, relationships carry information.

Source: Spring Data Neo4j - Chapter 4. Learning Neo4j

What is a Graph database?

A graph database stores data in a graph, the most generic of data structures, capable of elegantly representing any kind of data in a highly accessible way.

“A Graph —records data in→ Nodes —which have→ Properties”

“Nodes —are organized by→ Relationships —which also have→ Properties”

“A Traversal —navigates→ a Graph; it —identifies→ Paths —which order→ Nodes”

“An Index —maps from→ Properties —to either→ Nodes or Relationships”

“A Graph Database —manages a→ Graph and —also manages related→ Indexes”

Source: What is a Graph Database?

From Java to Neo4j

We have two Java classes representing our domain: User and Role. Here is the Class diagram:

# Cool UML Diagram
[User|id;firstName;lastName;username;password;role{bg:orange}]1--1> [Role|id;role{bg:green}]

In Neo4j, User and Role are nodes, and the link between the two is a relationship. In Part 2 we will demonstrate how to declare them as nodes and how to create the relationship.

Here's the Activity diagram:

http://yuml.me/diagram/activity/(start)-%3E%3Cd1%3Eview-%3E(Show%20Records)-%3E%7Ca%7C-%3E(end),%20%3Cd1%3Eadd-%3E(Show%20Form)-%3E%7Ca%7C,%20%3Cd1%3Eedit-%3E%3Cd2%3Ehas%20selected-%3E(Show%20Form)-%3E%7Ca%7C,%20%3Cd2%3Eno%20record%20selected-%3E(Popup%20Alert)-%3E%7Ca%7C,%20%3Cd1%3Edelete-%3E%3Cd3%3Ehas%20selected-%3E(Delete%20Record)-%3E%7Ca%7C,%20%3Cd3%3Eno%20record%20selected-%3E(Popup%20Alert)-%3E%7Ca%7C.

Screenshots

Let's preview how the application will look like after it's finished. This is also a good way to clarify further our application's specs. Note: These are the same screenshots you will see from the Spring MVC 3.1 - Implement CRUD with Spring Data MongoDB guide (We're reusing the exact presentation layer).

Entry page
The entry page is the primary page that users will see. It contains a table showing user records and four buttons for adding, editing, deleting, and reloading data. All interactions will happen in this page.

Entry page

Edit existing record
When user clicks the Edit button, an Edit Record form shall appear after the table.

Edit record form

When a user submits the form, a success or failure alert should appear.

Success alert

When the operation is successful, the update record should reflect on the table.

Edited record appears on the table

Create new record
When a user clicks the New button, a Create New Record form shall appear after the table.

Create new record form

When a user submits the form, a success or failure alert should appear.

Success alert

When the operation is successful, the new record should appear on the table.

New record shows on the form

Delete record
When user clicks the Delete button, a success or failure alert should appear.

Success alert

Reload record
When user clicks the Reload button, the data on the table should be reloaded.

Errors
When user clicks the Edit or Delete button without selecting a record first, a "Select a record first!" alert should appear.

Error alert

Next

In the next section, we will write the Java classes and discuss the application's layers. Click here to proceed.

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Spring MVC 3.1 - Implement CRUD with Spring Data Neo4j (Part 2)

Review

In the previous section, we have laid down the functional specs of the application and discussed the Neo4j data model. In this section, we will discuss the project's structure, write the Java classes, and map our domain classes to the Neo4j data model.

Table of Contents

Part 1: Introduction and Functional Specs
Part 2: Java classes
Part 3: XML configuration
Part 4: HTML (with AJAX)
Part 5: Running the Application

Project Structure

Our application is a Maven project and therefore follows Maven structure. As we create the classes, we've organized them in logical layers: domain, repository, service, and controller.

Here's a preview of our project's structure:

The Layers

Domain Layer

This layer contains the following POJOs:

• User - represents our user
• Role - represents the role of the user
• UserRoleRelationship - represents the relationship of a user to its role
.

Notice we've annotated our domain classes with Spring Data Neo4j annotations. Here are the explanations:

@NodeEntity

The @NodeEntity annotation is used to turn a POJO class into an entity backed by a node in the graph database. Fields on the entity are by default mapped to properties of the node. Fields referencing other node entities (or collections thereof) are linked with relationships.

Source: Spring Data Neo4j Reference

@GraphId

For the simple mapping this is a required field which must be of type Long. It is used by Spring Data Neo4j to store the node or relationship-id to re-connect the entity to the graph.

For the advanced mapping such a field is optional. Only if the underlying id has to be accessed, it is needed.

Source: Spring Data Neo4j Reference

@Indexed

@Indexed: Making entities searchable by field value

The @Indexed annotation can be declared on fields that are intended to be indexed by the Neo4j indexing facilities. The resulting index can be used to later retrieve nodes or relationships that contain a certain property value, e.g. a name. Often an index is used to establish the start node for a traversal.

Source: Spring Data Neo4j Reference

@Fetch

To have the collections of relationships being read eagerly ... we have to annotate it with the @Fetch annotation. Otherwise Spring Data Neo4j refrains from following relationships automatically.

Source: Spring Data Neo4j Reference

@RelatedTo

@RelatedTo: Connecting node entities

Every field of a node entity that references one or more other node entities is backed by relationships in the graph. These relationships are managed by Spring Data Neo4j automatically.

The simplest kind of relationship is a single field pointing to another node entity (1:1). In this case, the field does not have to be annotated at all, although the annotation may be used to control the direction and type of the relationship. When setting the field, a relationship is created when the entity is persisted. If the field is set to null, the relationship is removed.

Source: Spring Data Neo4j Reference

@RelationshipEntity

To access the full data model of graph relationships, POJOs can also be annotated with @RelationshipEntity, making them relationship entities. Just as node entities represent nodes in the graph, relationship entities represent relationships. As described above, fields annotated with @RelatedTo provide a way to link node entities together via relationships, but it provides no way of accessing the relationships themselves.

Relationship entities can be accessed via by @RelatedToVia-annotated

Fields in relationship entities are, similarly to node entities, persisted as properties on the relationship. For accessing the two endpoints of the relationship, two special annotations are available: @StartNode and @EndNode. A field annotated with one of these annotations will provide read-only access to the corresponding endpoint, depending on the chosen annotation.

Source: Spring Data Neo4j Reference

Controller Layer

This layer contains two controllers, MediatorController and UserController

• MediatorController is responsible for redirecting requests to appropriate pages. This isn't really required but it's here for organizational purposes.
• UserController is responsible for handling user-related requests such as adding and deleting of records

Service Layer

This layer contains a single service, UserService for managing users.

What is Spring Data Neo4j?

Spring Data Neo4j enables POJO based development for the Graph Database Neo4j. It maps annotated entity classes to the Neo4j Graph Database with advanced mapping functionality. The template programming model is equivalent to well known Spring templates and builds the basis for interaction with the graph and is also used for the advanced repository support.
Spring Data Neo4j is part of the Spring Data project which aims to provide convenient support for NoSQL databases.

Source: http://www.springsource.org/spring-data/neo4j

Utility classes

TraceInterceptor class is an AOP-based utility class to help us debug our application. This is a subclass of CustomizableTraceInterceptor (see Spring Data JPA FAQ)

Next

In the next section, we will focus on the configuration files for enabling Spring MVC. Click here to proceed.

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