Lynx

Lynx automatically exposes your JPA entities as a REST service with build-in metadata and query support using JAX-RS.

Usage

You can download the binaries from the releases page.

The project is split into two modules core and rest. The former contains all the main utilities, classes and helpers that use JPA to manipulate the data. The latter module contains the generic JAX-RS classes that use the core module to automatically expose your entities as a REST services. If you only want the utilities that are used behind the scenes and don't want to expose your entities as a REST service (or you want to do it on your own) only include the core module. However if you want to use everything then only include the rest module.

You can enable the Lynx by adding the following dependency to your project:

<dependency>
    <groupId>com.github.tfaga.lynx</groupId>
    <artifactId>lynx-core</artifactId>
    <version>${lynx.version}</version>
</dependency>

Getting started

JAX-RS

When implementing REST services the URI context information is needed. The URI can be obtained by adding UriInfo context to selected Resource:

@RequestScoped
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)
@Path("customers")
public class CustomerResource {

    @Context
    protected UriInfo uriInfo;

    @Inject
    private CustomerService customerBean;
}

Using the URI context information the query parameters can be constructed by using the QueryParameters class:

@GET
public Response getAllCustomers() {
    QueryParameters query = QueryParameters.query(uriInfo.getRequestUri().getQuery()).build();
    List<Customer> customers = customerBean.getCustomers(query);
    return Response.ok(customers).build();
}

CDI implementation

After parsing the query parameters they can be used to query or count entities using the JPAUtils class:

@RequestScoped
public class CustomerService {

    @PersistenceContext
    private EntityManager em;

    public List<Customer> getCustomers(QueryParameters query) {
        List<Customer> customers = JPAUtils.queryEntities(em, Customer.class, query);
        return customers;
    }


    public Long getCustomerCount(QueryParameters query) {
        Long count = JPAUtils.queryEntitiesCount(em, Customer.class, query);
        return count;
    }
}

We can also build the query using QueryStringDefaults class which applies the following defaults (if not specified by the client):

• max results: maximum number of entities that can be returned
• limit: default number of entities returned
• offset: default offset

@Context
private UriInfo uriInfo;

@Inject
private QueryStringDefaults qsd;

@Inject
private EntityManager em;

@GET
public Response getList() {
    QueryParameters query = qsd.builder().queryEncoded(uriInfo.getRequestUri().getRawQuery()).build();

    List<Customer> allCustomers = JPAUtils.queryEntities(em, Customer.class, query);
    Long allCustomersCount = JPAUtils.queryEntitiesCount(em, Customer.class, query);

    return Response.ok(allCustomers).header("X-Total-Count", allCustomersCount).build();
}

Defaults can either be constructed:

private QueryStringDefaults qsd = new QueryStringDefaults().maxLimit(100).defaultLimit(20).defaultOffset(0);

or injected with CDI and a producer class:

public class RestProducer {

    @Produces
    @ApplicationScoped
    public QueryStringDefaults getQueryStringDefaults() {
        return new QueryStringDefaults()
                .maxLimit(100)
                .defaultLimit(20)
                .defaultOffset(0);
    }
}

Examples

After the implementation of Rest resources and CDI beans, the query parameters can be used for pagination, sorting and filtering of JPA entities.

Pagination

The offset parameter indicates the position of the first entity which should be returned and the limit parameter indicates the number of entities.

GET /v1/customers?offset=10
GET /v1/customers?limit=5
GET /v1/customers?offset=10&limit=5

We must also return the number of all entities so the client can display correct number of page buttons. One way of doing this is with a custom HTTP header.

...
QueryParameters query = qsd.builder().queryEncoded(uriInfo.getRequestUri().getRawQuery()).build();

List<Customer> allCustomers = JPAUtils.queryEntities(em, Customer.class, query);
Long allCustomersCount = JPAUtils.queryEntitiesCount(em, Customer.class, query);

return Response.ok(allCustomers).header("X-Total-Count", allCustomersCount).build();

Sorting

Sorting of entities can be specified by providing the field and direction.

GET v1/customers?order=id DESC
GET v1/customers?order=lastName ASC

We can chain several sorts together.

GET v1/customers?order=email ASC,lastname DESC

After the last user specified sort, order by unique ID is automatically appended at the end of the query for deterministic sorting of same-valued columns.

Filtering

The entities can be filtered by using multiple operations:

• EQ | Equals
• EQIC | Equals ignore case
• NEQ | Not equal
• NEQIC | Not equal ignoring case
• LIKE | Pattern matching (% replaces characters, _ replaces a single character)
• LIKEIC | Pattern matching ignore case (% replaces characters, _ replaces a single character)
• GT | Greater than
• GTE | Greater than or equal
• LT | Lower than
• LTE | Lower than or equal
• IN | In set
• INIC | In set ignore case
• NIN | Not in set
• NINIC | Not in set ignore case
• ISNULL | Null
• ISNOTNULL | Not null

GET v1/customers?filter=id:EQ:1
GET v1/customers?filter=lastName:NEQIC:'doe'
GET v1/customers?filter=lastName:LIKE:H%
GET v1/customers?filter=age:GT:10
GET v1/customers?filter=id:IN:[1,2,3]
GET v1/customers?filter=lastName:ISNULL
GET v1/customers?filter=lastName:ISNOTNULL

GET v1/customers?filter=age:GT:10 id:IN:[1,2,3] lastName:ISNOTNULL

There are some special cases:

• If we want to use LIKE filter and query values that include a percent sign, it needs to be URL encoded (%25).
• Dates must be in ISO-8601 format, + sign must be URL encoded (%2B). Single quotes for value are required.

GET v1/customers?where=firstName:LIKE:'%somestring%25doe'
GET v1/customers?where=createdAt:GT:'2017-06-12T11:57:00%2B00:00'

Partial responses

We can select which fields we want returned in the resulting JSON with the fields parameter.

GET v1/customers?fields=firstName,lastName

Traversing OneToMany and ManyToOne relations

We can traverse entity attributes similar to JPQL style. Let's say each customer has many cars and we want to find owners of specific brand:

GET v1/cu
stomers?filter=cars.brand:EQ:bmw

It also works in reverse:

GET v1/cars?filter=customer.firstName:EQ:John

This would find all Cars that have an owner named John.

Combine pagination, sorting and filtering

Pagination, sorting and filtering of entities can be combined by separating them with &.

GET /v1/customers?offset=10&limit=5&order=id DESC&filter=age:GT:10 id:IN:[1,2,3] lastName:ISNOTNULL

Filters are chained together with AND operator. OR WHERE clause is not supported at this time.

Additional criteria query manipulation

Predicate constructed from query parameters can be further changed. For example:

List<Customer> allCustomers = JPAUtils.queryEntities(em, Customer.class,
      (p, cb, r) -> cb.and(p, cb.equal(r.get("firstName"), "John")));

Where:

• p is existing Predicate
• cb is CriteriaBuilder and
• c is Root

With this, programmer has the full power of Criteria API to further manipulate the query.

Building

Ensure you have JDK 8 (or newer), Maven 3.2.1 (or newer) and Git installed

    java -version
    mvn -version
    git --version

First clone the Lynx repository:

    git clone https://github.com/TFaga/lynx.git
    cd lynx

To build Lynx run:

    mvn install

This will build all modules and run the testsuite.

Once completed you will find the build archives in the modules respected target folder.

Changelog

Recent changes can be viewed on Github on the Releases Page

Contribute

See the contributing docs

When submitting an issue, please follow the guidelines.

When submitting a bugfix, write a test that exposes the bug and fails before applying your fix. Submit the test alongside the fix.

When submitting a new feature, add tests that cover the feature.

License

MIT