library client

Library client

This section shows how to generate and use Epigraph client.

Project setup

Lets start by creating new module: library-service. Here's full pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <artifactId>examples-library-client</artifactId>

  <parent>
    <groupId>ws.epigraph.examples</groupId>
    <artifactId>examples-library</artifactId>
    <version>0.0.2-SNAPSHOT</version>
  </parent>

  <dependencies>
    <dependency>
      <groupId>${project.parent.groupId}</groupId>
      <artifactId>examples-library-schema</artifactId>
      <version>${project.parent.version}</version>
    </dependency>

    <dependency>
      <groupId>ws.epigraph</groupId>
      <artifactId>epigraph-java-http-client</artifactId>
      <version>0.0.2-SNAPSHOT</version>
    </dependency>

  </dependencies>

  <build>
    <plugins>

      <plugin>
        <groupId>ws.epigraph</groupId>
        <artifactId>epigraph-java-maven-plugin</artifactId>
        <configuration><client/></configuration>
      </plugin>

      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>exec-maven-plugin</artifactId>
        <version>1.2.1</version>
        <configuration>
          <mainClass>ws.epigraph.examples.library.LibraryClient</mainClass>
        </configuration>
      </plugin>

    </plugins>
  </build>

</project>

Important things:

• Dependency on library schema is obvious
• epigraph-java-http-client is needed by generated client code
• <client/> configuration instructs Epigraph plugin to generate the client

Don't forget to add <module>library-client</module> to the parent pom.

Now we can generate the client:

mvn -pl library-client generate-sources

This produces BooksClient class.

Example code

Lets use it. Here's a simple application to demonstrate how to call all supported operations. Notice that projections are passed as strings for now, this will be improved in the future.

package ws.epigraph.examples.library;

import org.apache.http.HttpHost;
import org.apache.http.impl.nio.client.CloseableHttpAsyncClient;
import org.apache.http.impl.nio.client.HttpAsyncClients;
import ws.epigraph.examples.library.resources.books.client.BooksClient;

import java.io.IOException;
import java.util.concurrent.ExecutionException;

public class LibraryClient {
  public static final int PORT = 8888;
  public static final String HOST = "localhost";

  public static void main(String[] args) throws IOException, ExecutionException, InterruptedException {

    try (CloseableHttpAsyncClient httpClient = HttpAsyncClients.createDefault()) {
      httpClient.start();
      BooksClient client = new BooksClient(new HttpHost(HOST, PORT), httpClient);

      //                                          create a book
      BookId_List createdIds = client.create(
          null, // no input projection
          BookRecord_List.create()
              .add(BookRecord.create()
                  .setAuthor(Author.create().setId(AuthorId.create(1L)))
                  .setTitle("Quantum Physics for Dummies")
                  .setText(Text.create()
                      .setPlain(PlainText.create(
                          "One of the central problems of quantum mechanics is to calculate the energy levels of a " +
                          "system. The energy operator, called the Hamiltonian, abbreviated H, gives you the " +
                          "total energy.")
                      )
                  )
              ),
          "*" // output projection: get all list elements
      ).get();// it's a Future, so we have to get()

      BookId createdId = createdIds.datums().iterator().next(); // not checking for errors to keep things simple


      //                                          search
      BookId_BookRecord_Map booksByAllan = client.readSearchByAuthor(";author={firstName:'Allan'}[](title)").get();

      System.out.println("Books by Allan:");
      for (BookRecord bookRecord : booksByAllan.datums().values()) {
        System.out.println(bookRecord.getTitle());
      }


      //                                          update
      client.update(
          null, // no update projection
          BookId_BookRecord_Map.create()  // change created book's author id to 2
              .put(createdId, BookRecord.create().setAuthor(Author.create().setId(AuthorId.create(2L)))),
          "" // not interested in output
      );


      //                                          read
      BookId_BookRecord_Map booksMap =
          client.read("[" + createdId + "](+author:+record(+firstName,+lastName))").get(); // '+' is 'required'
      BookRecord bookRecord = booksMap.datums().get(createdId.toImmutable());
      AuthorRecord authorRecord = bookRecord.getAuthor().getRecord();
      System.out.println("\nNew author: " + authorRecord.getFirstName() + " " + authorRecord.getLastName());


      //                                          delete
      client.delete("[" + createdId + "]", "");
    }

  }
}

Running

First start the server:

mvn -pl library-service exec:java

Then our example (in another terminal):

mvn -pl library-client exec:java

Output should be:

Books by Allan:
The Gold Bug
Quantum Physics for Dummies

New author: Arthur Doyle