Java EE 7 with Angular JS – Part 1

Today’s post will show you how to build a very simple application using Java EE 7 and Angular JS. Before going there let me tell you a brief story:

I have to confess that I was never a big fan of Javascript, but I still remember the first time I have used it. I don’t remember the year exactly, but probably around mid 90′s. I had a page with 3 frames (yes frames! remember those? very popular around that time) and I wanted to reload 2 frames when I clicked a link on the 3rd frame. At the time, Javascript was used to do some fancy stuff on webpages, not every browser have Javascript support and some even required you to turn it on. Fast forwarding to today the landscaped changed dramatically. Javascript is a full development stack now and you can develop entire applications written only in Javascript. Unfortunately for me, sometimes I still think I’m back in the 90′s and don’t give enough credit to Javascript, so this is my attempt to get to know Javascript better.

Why Java EE 7?

Well, I like Java and the new Java EE version is pretty good. Less verbose and very fast using Wildfly or Glassfish. It provides you with a large set of specifications to suit your needs and it’s a standard in the Java world.

Why Angular JS?

I’m probably following the big hype around Angular here. Since I don’t have much experience with Javascript I don’t know the offers very well, so I’m just following advice of some friends and I have also noticed a big acceptance of Angular in the last Devoxx. Every room with an Angular talk was full, so I wanted to give it a try and found out for myself.

The Application

For the application, it’s a simple list with pagination and a REST service that feeds the list data. Every time I start a new enterprise project it’s usually the first thing we code: create a table, store some data and list some random data, so I think it’s appropriate.

The Setup

• Java EE 7
• Angular JS
• ng-grid
• UI Bootstrap
• Wildfly

The Code (finally!)

Backend – Java EE 7

Starting with the backend, let’s define a very simple Entity class (some code is omitted for simplicity):

Person.java

@Entity
public class Person {
    @Id
    private Long id;

    private String name;

    private String description;

}

If you’re not familiar with Java EE JPA specification, this will allow to model an object class into a database table by using the annotation @Entity to connect to the database table with the same name and the annotation @Id to identify the table primary key.

Following by a persistence.xml:

persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1"
             xmlns="http://xmlns.jcp.org/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="myPU" transaction-type="JTA">
        <properties>
            <property name="javax.persistence.schema-generation.database.action" value="drop-and-create"/>
            <property name="javax.persistence.schema-generation.create-source" value="script"/>
            <property name="javax.persistence.schema-generation.drop-source" value="script"/>
            <property name="javax.persistence.schema-generation.create-script-source" value="sql/create.sql"/>
            <property name="javax.persistence.schema-generation.drop-script-source" value="sql/drop.sql"/>
            <property name="javax.persistence.sql-load-script-source" value="sql/load.sql"/>
        </properties>
    </persistence-unit>
</persistence>

Two of my favourite new features on Java EE 7: now you can run sql in a standard way by using the properties javax.persistence.schema-generation.* and it also binds you to a default datasource if you don’t provide one. So for this case, it’s going to use the internal Wildfly H2 database for our application.

Finally, to provide the list data we need to query the database and expose it as a REST service:

PersonResource.java

@Stateless
@ApplicationPath("/resources")
@Path("persons")
public class PersonResource extends Application {
    @PersistenceContext
    private EntityManager entityManager;

    private Integer countPersons() {
        Query query = entityManager.createQuery("SELECT COUNT(p.id) FROM Person p");
        return ((Long) query.getSingleResult()).intValue();
    }

    @SuppressWarnings("unchecked")
    private List<Person> findPersons(int startPosition, int maxResults, String sortFields, String sortDirections) {
        Query query = entityManager.createQuery("SELECT p FROM Person p ORDER BY " + sortFields + " " + sortDirections);
        query.setFirstResult(startPosition);
        query.setMaxResults(maxResults);
        return query.getResultList();
    }

    public PaginatedListWrapper<Person> findPersons(PaginatedListWrapper<Person> wrapper) {
        wrapper.setTotalResults(countPersons());
        int start = (wrapper.getCurrentPage() - 1) * wrapper.getPageSize();
        wrapper.setList(findPersons(start,
                                    wrapper.getPageSize(),
                                    wrapper.getSortFields(),
                                    wrapper.getSortDirections()));
        return wrapper;
    }

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public PaginatedListWrapper<Person> listPersons(@DefaultValue("1")
                                                    @QueryParam("page")
                                                    Integer page,
                                                    @DefaultValue("id")
                                                    @QueryParam("sortFields")
                                                    String sortFields,
                                                    @DefaultValue("asc")
                                                    @QueryParam("sortDirections")
                                                    String sortDirections) {
        PaginatedListWrapper<Person> paginatedListWrapper = new PaginatedListWrapper<>();
        paginatedListWrapper.setCurrentPage(page);
        paginatedListWrapper.setSortFields(sortFields);
        paginatedListWrapper.setSortDirections(sortDirections);
        paginatedListWrapper.setPageSize(5);
        return findPersons(paginatedListWrapper);
    }
}

The code is exactly as a normal Java POJO, but using the Java EE annotations to enhance the behaviour. @ApplicationPath("/resources") and @Path("persons") will expose the REST service at the url yourdomain/resources/persons, @GET marks the logic to be called by the http GET method and @Produces(MediaType.APPLICATION_JSON) formats the REST response as JSON format. Pretty cool with only a few annotations.

To make it a little easier to exchange the needed information for the paginated list, I have also created the following wrapper class:

PaginatedListWrapper.java

public class PaginatedListWrapper<T> {
    private Integer currentPage;
    private Integer pageSize;
    private Integer totalResults;

    private String sortFields;
    private String sortDirections;
    private List<T> list;
}

And we are done with the backend stuff.

UI – Angular JS

To display the data we are going to use Angular JS. Angular extends the traditional HTML with additional custom tag attributes to bind data represented in Javascript variables by following a MVC approach. So, lets look to our html page:

index.html

<!DOCTYPE html>
<!-- Declares the root element that allows behaviour to be modified through Angular custom HTML tags. -->
<html ng-app="persons">
<head>
    <title></title>
    <script src="lib/angular.min.js"></script>
    <script src="lib/jquery-1.9.1.js"></script>
    <script src="lib/ui-bootstrap-0.10.0.min.js"></script>
    <script src="lib/ng-grid.min.js"></script>

    <script src="script/person.js"></script>

    <link rel="stylesheet" type="text/css" href="lib/bootstrap.min.css"/>
    <link rel="stylesheet" type="text/css" href="lib/ng-grid.min.css"/>
    <link rel="stylesheet" type="text/css" href="css/style.css"/>
</head>

<body>

<br>

<div class="grid">
    <!-- Specify a JavaScript controller script that binds Javascript variables to the HTML.-->
    <div ng-controller="personsList">
        <!-- Binds the grid component to be displayed. -->
        <div class="gridStyle" ng-grid="gridOptions"></div>

        <!--  Bind the pagination component to be displayed. -->
        <pagination direction-links="true" boundary-links="true"
                    total-items="persons.totalResults" page="persons.currentPage" items-per-page="persons.pageSize"
                    on-select-page="refreshGrid(page)">
        </pagination>
    </div>
</div>

</body>
</html>

Apart from the Javascript and CSS declarations there is very little code in there. Very impressive. Angular also have a wide range of ready to use components, so I’m using the ng-grid to display the data and UI Bootstrap that provides a pagination component. The ng-grid also have a pagination component, but I liked the UI Bootstrap pagination component more.

There is something still missing. The Javascript file where everything happens:

person.js

var app = angular.module('persons', ['ngGrid', 'ui.bootstrap']);
// Create a controller with name personsList to bind to the html page.
app.controller('personsList', function ($scope, $http) {
    // Makes the REST request to get the data to populate the grid.
    $scope.refreshGrid = function (page) {
        $http({
            url: 'resources/persons',
            method: 'GET',
            params: {
                page: page,
                sortFields: $scope.sortInfo.fields[0],
                sortDirections: $scope.sortInfo.directions[0]
            }
        }).success(function (data) {
            $scope.persons = data;
        });
    };

    // Do something when the grid is sorted.
    // The grid throws the ngGridEventSorted that gets picked up here and assigns the sortInfo to the scope.
    // This will allow to watch the sortInfo in the scope for changed and refresh the grid.
    $scope.$on('ngGridEventSorted', function (event, sortInfo) {
        $scope.sortInfo = sortInfo;
    });

    // Watch the sortInfo variable. If changes are detected than we need to refresh the grid.
    // This also works for the first page access, since we assign the initial sorting in the initialize section.
    $scope.$watch('sortInfo', function () {
        $scope.refreshGrid($scope.persons.currentPage);
    }, true);

    // Initialize required information: sorting, the first page to show and the grid options.
    $scope.sortInfo = {fields: ['id'], directions: ['asc']};
    $scope.persons = {currentPage : 1};
    $scope.gridOptions = {
        data: 'persons.list',
        useExternalSorting: true,
        sortInfo: $scope.sortInfo
    };
});

The Javascript code is very clean and organised. Notice how everything gets added to an app controller, allowing you to have multiple separation of concerns on your business logic. To implement the required behaviour we just need to add a few functions to refresh the list by calling our REST service and monitor the grid data to refresh the view. This is the end result:

Next Steps:

For the following posts related with these series, I’m planning to:

• Implement filtering
• Implement detail view
• Implement next / prev browsing
• Deploy in the cloud
• Manage Javascript dependencies

Resources

You can clone a full working copy from my github repository and deploy it to Wildfly. You can find instructions there to deploy it. Should also work on Glassfish.

Java EE – Angular JS Source

Update

In the meanwhile I have updated the original code with the post about Manage Javascript dependencies. Please, download the original source of this post from the release 1.0. You can also clone the repo, and checkout the tag from release 1.0 with the following command: git checkout 1.0.

I hope you enjoyed the post! Let me know if you have any comments about this.

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