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Spring Roo in Action is an insightful and comprehensive treatment of Spring Roo. Velocity, FreeMarker, or even using PDF or Excel. Spring. Spring Roo in Action is a unique book that teaches you how to code Java in Roo, with a particular focus on Spring-based applications. Through hands-on. In the last chapter, we discussed Spring Roo from a developer's perspective. We discussed the various component types, and how the Roo shell creates and.
The article assumes some familiarity with Spring Roo. Spring Roo scaffolds controllers and views from entities classes. Views are created with components from the tagx library. Without further ado. Straight to business. This article refers to forms implemented in World Almanac by jD website.
Roo application architecture models. Getting started with Roo 2. Working with the Roo shell.
Database persistence with entities 3. Your business objects and persistence. Validating Courses with Bean Validation. Relationships, JPA, and advanced persistence 4. Object relations: A sample Course Manager database.
Reverse engineering your database. Rapid web applications with Roo 5.
Monitoring messaging activity. Roo add-ons Extending Roo with add-ons. Working with published Roo add-ons. Adding a language to Roo with i18n. Advanced add-ons and deployment Advanced add-ons. To create an advanced add-on, you need Coffee Script.
Key add-on beans and services. Cloud computing What is cloud computing? Deploying the Course Manager application to the cloud. Application monitoring in the cloud. Workflow applications using Spring Integration Workflow applications. Using the Spring Integration framework.
Assign tags to our tasks, so that we can search for them later. One-to-many—tasks and projects In our task tracking system, we would like to place tasks into projects, so that they can be more easily managed. We will limit the functionality to one project per task in our case.
Entity; import org. RooJavaBean; import org. RooToString; import org. Here is the code for the Roo-generated Project Java class Open up ProjectIntegrationTest. The resulting method should look like listing 1.
This test creates a new Project instance, and then uses the TaskDataOnDemand class to create a new dummy Task object, making it quick for us to get started testing our relationship with Project. It then tells the Project instance to persist itself. Finally, the test fetches the project from scratch and asserts that the newly found instance contains the same number of tasks.
More tests could be performed, such as testing for primary key equality, but this test will suffice for a basic straw test of the framework. Note that, by saving the Project, the tasks get saved automatically. Why annotate with Transactional?
You will notice that the Transactional annotation has been added to this test method. In order to perform the load, a connection to the database must be established. The Transactional annotation tells Spring and JPA to keep the same connection active until the end of the annotated method. To see what happens without the Transactional annotation, remove it and test again.
You will see a LazyInstantiationException when the p2. This can be modified but is usually the default behavior. At this point, we have to make a decision—do we want to support navigation from the parent to the child and also from the child back to the parent? This depends on whether you want to provide a way for Tasks to find their Project.
In the case of our system, we do, since we would like to load a list of all tasks and, for each one, display the Project information. Many-to-one—tasks access projects Loading a project and navigating to see the collection of tasks is a pretty straightforward thing. Setting up the reverse navigation from a Task to its parent Project is easy. Task --fieldName project --type org. We can do that by adding the —class parameter to our command. This is just another way to run commands in Roo without worrying about switching focus among a number of entities.
The preceding command performs the following tasks: Defines a field in the Task object named project, which is a reference to a Project entity.
Adds a ManyToOne annotation, which references the relationship to the Project class. Adds a JoinColumn annotation, which denotes that a foreign key must be mapped in the resulting table, referring to the primary key of the parent table. We can now load a Task and fetch the parent Project object, in addition to loading a Project instance and requesting all of the held Task entities within the tasks field.
This is an alternate form of mapping for a one-to-many relationship.
For more information about the details of JPA 2. Add the code in listing 2. The main difference between this and the preceding test method is that we now must establish both sides of the relationship—we add the new Task to the Project.
The persist method still modifies both items since we are saving from the parent. However, with the bidirectional relationship established, even saving from the child to the parent works, based on the reachability concept.
Try changing the test to use randomTask. Finders write JPA query code for you. To get the most out of Roo, we highly suggest you learn and master JPA. This lets us mark any task with a tag or label so that we can allow users to organize their own categories.
We are going to use a many-to-many relationship, which establishes that any row in one entity can be attached to any other row in the other entity. In database terms, we are establishing two tables, each with a one-to-many relationship to a middle table, which contains rows with a combination of primary keys from each of the parent tables, as shown in figure 2. For the sake of management, we need to assign a relationship owner. In a one-to-many relationship, the owner is the parent.
For a many-to-many relationship, this is an arbitrary selection.
First, the Task entity is augmented with a relationship to ActivityTag: package org. The ActivityTag class will be amended with the following collection: package org.
Many-to-many strategies Implementing a many-to-many relationship in a relational database always involves three tables. The database design strategy is to create a table in the middle and map a one-to-many relationship from each of the outer tables into the new table.
As a JPA developer, you have a choice whether you want this relationship to be modeled as a many-to-many object relationship, or by decomposing it yourself into two one-to-many relationships to this intersecting table. The general rule is that, when you have to add attributes to the intersection, you want to set up all three entities.