Coding Day - Backend

This is a simple project to help you get going with the backend coding day.

It's a Spring Boot application with H2 database and jOOQ to access the database in a type safe way.

Development will happen in IntelliJ, the project is already added and can be easily run from there.

Project structure

• Source code is located under src/main/java. Add your code there.
• Tests are located under src/test/java. Add your unit tests there.
• Running the application will create a file-based database (very simple DB with some tables)
• Database models are already generated by jOOQ and can be found in package net.comerge.codingday.backend.database.models.
• See controllers package (net.comerge.codingday.backend.controllers) to add new REST end-points.
• If you change the database schema and want to regenerate models with jOOQ:
  • Start the project (MainApplication)
  • Stop the project
  • Then run mvn jooq-codegen:generate on the console or from the IntelliJ maven tab
• You can add additional dependencies to the pom.xml if you want to use some external library.

Running the application

Running MainApplication is all you need.

Spring will then start an embedded Tomcat and deploy the application there.

There are two test REST endpoint which can be reached at http://localhost:8080/v1/test and http://localhost:8080/v1/public/users

Using Postman (https://www.getpostman.com/) instead of the browser allows you to also send data via HTTP POST to the backend.

Running the unit tests

Right-click a test and select Run ... to execute a test.

Assessment

Non exhaustive list of items that will be assessed:

• App architecture
• API consumption
• Understanding of object-oriented programming principles
• Unit tests
• Code readability/correctness
• Time management
• ...

Your tasks

Context: We received a request from one of our international clients that they need an app that shows company-internal news. The user should also be able to view different teams and their members. For this the backend needs to provide the necessary data.

You will implement the backend based on the design/data model present and the required endpoints.

Implement the following endpoints as far as the time allows:

1. GET /public/users/{id} Should deliver a JSON object of a single user with the given id (all fields).
2. POST /public/users Should create a new user. Keep in mind that the database will create a primary key (ID) for you.
3. GET /public/teams Should deliver a list of teams with three fields per team: id, name and number of users in the team. First fetch all teams and then count the number of users for each team separately. Performance is not a issue here.
4. GET /public/teams/{id} Should deliver a JSON object of a single team with the given id (all fields) together with a list of users of the team.
5. GET /public/news Should deliver a list of news with all fields, sorted by created_at descending.
6. GET /public/news/{id} Should deliver a JSON object of a single news with the given id (all fields).
7. Extend the GET /public/users It should be possible to optionally filter the user list by username (or username parts). Use query parameters to send the optional filter, e.g. /public/users?username=rico
8. Extend the GET /public/news It should be possible to optionally filter the news list by title or message (or parts of them) or by author id. Use query parameters for the optional filters, e.g. /public/news?authorId=3&filter=foo

For each endpoint write integration tests.

jOOQ

jOOQ is a framework which allows you to write SQL statements directly in java code in a type safe way. It's not a Object-Rational mapper but it provides meta data which is generated from a existing database schema.

You can inject a DSLContext into your class and use this to write queries. E.g. to select some users you might write

// SQL
SELECT * 
    FROM user 
    WHERE user.first_name ILIKE '%rico%';

// jOOQ
context.select()
        .from(User.USER)
        .where(User.USER.FIRST_NAME.likeIgnoreCase("%rico%"))
        .fetchInto(UserRecord.class);

The SQL syntax can be translated more or less directly into jOOQ syntax and the generated meta data classes (e.g. User.USER) helps with type safety.

Of course you can also insert data:

context.insertInto(User.USER)
        .set(User.USER.FIRST_NAME, "new")
        .set(User.USER.LAST_NAME, "user")
        .set(User.USER.EMAIL, "[email protected]")
        .execute();

// or alternatively

final UserRecord record = context.newRecord(User.USER);
record.setFirstName("new");
record.setLastName("user");
record.setEmail("[email protected]");
record.store();

Be aware that the primary key is generated automatically by the database.

lombok

To make live a bit easier we use lombok to implement our DTOs. This tool will help you to reduce boilerplate code by adding some annotations allowing you to skip writing getters and setters for example.

For example this two classes are the same:

// normal java class

public class SimpleDTO {
    private String first;
    private int second;

    public SimpleDTO setFirst(String first) {
        this.first = first;
        return this;
    }
    public String getFrist() {
        return first;
    }

    public SimpleDTO setSecond(int second) {
        this.second = second;
        return this;
    }
    public int getSecond() {
        return second;
    }
}

// or with lombok

@Data                    // generate getters, setters and implements equals()
@ToString                // generate toString()
@Accessors(chain = true) // have the `return this;` in the setters
public class SimpleDTO {
    private String first;
    private int second;
}

assertJ

We use assertJ for unit tests. It provides you with a lot of nice and convenient functionality. You almost always write it like this assertThat(valueUnderTest).isHasSomething(expectedValue) E.g.

assertThat(23).isEqualTo(23);
assertThat(someObject).isNotNull();
assertThat(someListLikeThing).hasSize(23);
assertThat(someListLikeThing).containsExactlyInAnyOrder(23, 11, 42);
assertThat(someObject.getName()).isNotNull().startsWith("Ric");

The assertThat(value) method provides a lot of functions depending on the given value which can be seen by using the IDEs completion (e.g. CTRL+Space).

Some helpful links

• https://spring.io/guides
• https://www.jooq.org/
• https://projectlombok.org/
• http://joel-costigliola.github.io/assertj/