idea 构建spring_以Spring方式构建企业Java应用程序

idea 构建spring

我认为可以说Java EE在Java开发人员中享有很高的声誉。尽管多年来确实在各个方面都有所改善，甚至将其改名为Eclipse Foundation成为Jakarta EE ，但其苦味仍然相当强烈。另一方面，我们拥有Spring框架（或者为了更好地反映现实，一个成熟的Spring平台）：出色，轻巧，快速，创新和高产的Java EE替代品。那么，为什么要打扰Java EE ？

我们将通过展示使用大多数Java EE规范构建现代Java应用程序有多么容易来回答这个问题。成功的关键要素是Eclipse Microprofile ：微服务时代的企业Java。

如此简单，我们将要构建的应用程序就是RESTful Web API来管理人员。在Java中构建RESTful Web服务的标准方法是使用JAX-RS 2.1 （ JSR-370 ）。因此， CDI 2.0 （ JSR-365 ）将负责依赖注入，而JPA 2.0 （ JSR-317 ）将涵盖数据访问层。当然， Bean Validation 2.0 （ JSR-380 ）正在帮助我们处理输入验证。

我们将要依赖的唯一非Java EE规范是OpenAPI v3.0 ，它有助于提供RESTful Web API的可用描述。这样，让我们开始使用PersonEntity域模型（将getter和setter省略为不太相关的细节）：

@Entity
@Table(name = "people")
public class PersonEntity {@Id @Column(length = 256) private String email;@Column(nullable = false, length = 256, name = "first_name")private String firstName;@Column(nullable = false, length = 256, name = "last_name")private String lastName;@Versionprivate Long version;
}

它只是具有绝对最小的一组属性。 JPA存储库非常简单，并实现了一组典型的CRUD方法。

@ApplicationScoped
@EntityManagerConfig(qualifier = PeopleDb.class)
public class PeopleJpaRepository implements PeopleRepository {@Inject @PeopleDb private EntityManager em;@Override@Transactional(readOnly = true)public Optional<PersonEntity> findByEmail(String email) {final CriteriaBuilder cb = em.getCriteriaBuilder();final CriteriaQuery<PersonEntity> query = cb.createQuery(PersonEntity.class);final Root<PersonEntity> root = query.from(PersonEntity.class);query.where(cb.equal(root.get(PersonEntity_.email), email));try {final PersonEntity entity = em.createQuery(query).getSingleResult();return Optional.of(entity);} catch (final NoResultException ex) {return Optional.empty();}}@Override@Transactionalpublic PersonEntity saveOrUpdate(String email, String firstName, String lastName) {final PersonEntity entity = new PersonEntity(email, firstName, lastName);em.persist(entity);return entity;}@Override@Transactional(readOnly = true)public Collection<PersonEntity> findAll() {final CriteriaBuilder cb = em.getCriteriaBuilder();final CriteriaQuery<PersonEntity> query = cb.createQuery(PersonEntity.class);query.from(PersonEntity.class);return em.createQuery(query).getResultList();}@Override@Transactionalpublic Optional<PersonEntity> deleteByEmail(String email) {return findByEmail(email).map(entity -> {em.remove(entity);return entity;});}
}

事务管理（即@Transactional批注）需要一些解释。在典型的Java EE应用程序中，容器运行时负责管理事务。由于我们不想随身携带应用程序容器，而是保持精简，因此我们可以使用EntityManager来启动/提交/回滚事务。当然可以解决，但会污染样板代码。可以说，更好的选择是使用Apache DeltaSpike CDI扩展进行声明式事务管理（这是@Transactional和@EntityManagerConfig注释的来源）。下面的代码段说明了如何进行集成。

@ApplicationScoped
public class PersistenceConfig {@PersistenceUnit(unitName = "peopledb")private EntityManagerFactory entityManagerFactory;@Produces @PeopleDb @TransactionScopedpublic EntityManager create() {return this.entityManagerFactory.createEntityManager();}public void dispose(@Disposes @PeopleDb EntityManager entityManager) {if (entityManager.isOpen()) {entityManager.close();}}
}

太棒了，最难的部分已经过去了！接下来是人员数据传输对象和服务层。

public class Person {@NotNull private String email;@NotNull private String firstName;@NotNull private String lastName;
}

老实说，为了使示例应用程序尽可能小，我们可以完全跳过服务层，直接进入存储库。但这通常不是一个很好的做法，因此无论如何让我们介绍PeopleServiceImpl 。

@ApplicationScoped
public class PeopleServiceImpl implements PeopleService {@Inject private PeopleRepository repository;@Overridepublic Optional<Person> findByEmail(String email) {return repository.findByEmail(email).map(this::toPerson);}@Overridepublic Person add(Person person) {return toPerson(repository.saveOrUpdate(person.getEmail(), person.getFirstName(), person.getLastName()));}@Overridepublic Collection<Person> getAll() {return repository.findAll().stream().map(this::toPerson).collect(Collectors.toList());}@Overridepublic Optional<Person> remove(String email) {return repository.deleteByEmail(email).map(this::toPerson);}private Person toPerson(PersonEntity entity) {return new Person(entity.getEmail(), entity.getFirstName(), entity.getLastName());}
}

剩下的唯一部分是JAX-RS应用程序和资源的定义。

@Dependent
@ApplicationPath("api")
@OpenAPIDefinition(info = @Info(title = "People Management Web APIs", version = "1.0.0", license = @License(name = "Apache License", url = "https://www.apache.org/licenses/LICENSE-2.0"))
)
public class PeopleApplication extends Application {
}

不多说，可能就这么简单。不过， JAX-RS资源实现更加有趣（ OpenAPI注释占据了大部分位置）。

@ApplicationScoped
@Path( "/people" ) 
@Tag(name = "people")
public class PeopleResource {@Inject private PeopleService service;@Produces(MediaType.APPLICATION_JSON)@GET@Operation(description = "List all people", responses = {@ApiResponse(content = @Content(array = @ArraySchema(schema = @Schema(implementation = Person.class))),responseCode = "200")})public Collection<Person> getPeople() {return service.getAll();}@Produces(MediaType.APPLICATION_JSON)@Path("/{email}")@GET@Operation(description = "Find person by e-mail", responses = {@ApiResponse(content = @Content(schema = @Schema(implementation = Person.class)), responseCode = "200"),@ApiResponse(responseCode = "404", description = "Person with such e-mail doesn't exists")})public Person findPerson(@Parameter(description = "E-Mail address to lookup for", required = true) @PathParam("email") final String email) {return service.findByEmail(email).orElseThrow(() -> new NotFoundException("Person with such e-mail doesn't exists"));}@Consumes(MediaType.APPLICATION_JSON)@Produces(MediaType.APPLICATION_JSON)@POST@Operation(description = "Create new person",requestBody = @RequestBody(content = @Content(schema = @Schema(implementation = Person.class)),), responses = {@ApiResponse(content = @Content(schema = @Schema(implementation = Person.class)),headers = @Header(name = "Location"),responseCode = "201"),@ApiResponse(responseCode = "409", description = "Person with such e-mail already exists")})public Response addPerson(@Context final UriInfo uriInfo,@Parameter(description = "Person", required = true) @Valid Person payload) {final Person person = service.add(payload);return Response.created(uriInfo.getRequestUriBuilder().path(person.getEmail()).build()).entity(person).build();}@Path("/{email}")@DELETE@Operation(description = "Delete existing person",responses = {@ApiResponse(responseCode = "204",description = "Person has been deleted"),@ApiResponse(responseCode = "404", description = "Person with such e-mail doesn't exists")})public Response deletePerson(@Parameter(description = "E-Mail address to lookup for", required = true ) @PathParam("email") final String email) {return service.remove(email).map(r -> Response.noContent().build()).orElseThrow(() -> new NotFoundException("Person with such e-mail doesn't exists"));}
}

至此，我们完成了！但是，我们如何将所有这些部件组装并连接在一起？这是Microprofile进入舞台的时间。有很多实现可供选择，本文中将使用的是Project Hammock 。我们唯一要做的就是指定我们要使用的CDI 2.0 ， JAX-RS 2.1和JPA 2.0实现，它们分别转换为Weld ， Apache CXF和OpenJPA （通过Project Hammock依赖关系表示）。让我们看一下Apache Maven pom.xml文件。

<properties><deltaspike.version>1.8.1</deltaspike.version><hammock.version>2.1</hammock.version>
</properties><dependencies><dependency><groupId>org.apache.deltaspike.modules</groupId><artifactId>deltaspike-jpa-module-api</artifactId><version>${deltaspike.version}</version><scope>compile</scope></dependency><dependency><groupId>org.apache.deltaspike.modules</groupId><artifactId>deltaspike-jpa-module-impl</artifactId><version>${deltaspike.version}</version><scope>runtime</scope></dependency><dependency><groupId>ws.ament.hammock</groupId><artifactId>dist-microprofile</artifactId><version>${hammock.version}</version></dependency><dependency><groupId>ws.ament.hammock</groupId><artifactId>jpa-openjpa</artifactId><version>${hammock.version}</version></dependency><dependency><groupId>ws.ament.hammock</groupId><artifactId>util-beanvalidation</artifactId><version>${hammock.version}</version></dependency><dependency><groupId>ws.ament.hammock</groupId><artifactId>util-flyway</artifactId><version>${hammock.version}</version></dependency><dependency><groupId>ws.ament.hammock</groupId><artifactId>swagger</artifactId><version>${hammock.version}</version></dependency>
</dependencies>

事不宜迟，让我们立即构建并运行该应用程序（如果您好奇应用程序正在使用什么关系数据存储，则它是H2 ，并且内存中配置了数据库）。

> mvn clean package
> java -jar target/eclipse-microprofile-hammock-0.0.1-SNAPSHOT-capsule.jar

确保我们的人员管理RESTful Web API正常运行的最佳方法是向其发送几个请求：

>  curl -X POST http://localhost:10900/api/people -H "Content-Type: application\json" \-d '{"email": "a@b.com", "firstName": "John", "lastName": "Smith"}'HTTP/1.1 201 Created
Location: http://localhost:10900/api/people/a@b.com
Content-Type: application/json{"firstName":"John",""lastName":"Smith","email":"a@b.com"
}

如何确保Bean验证正常工作呢？要触发该请求，让我们发送部分准备好的请求。

>  curl  --X POST http://localhost:10900/api/people -H "Content-Type: application\json" \-d '{"firstName": "John", "lastName": "Smith"}'HTTP/1.1 400 Bad Request
Content-Length: 0

您还可以在http：// localhost：10900 / index.html？url = http：// localhost：10900 / api / openapi.json上获得OpenAPI规范和预先捆绑的Swagger UI分发。

Java应用

到目前为止，到目前为止还算不错，但实际上我们还没有谈论过测试应用程序。假设要增加一个人，要进行集成测试有多难？事实证明，围绕测试Java EE应用程序的框架有了很大的改进。特别是，使用Arquillian测试框架（以及最受欢迎的JUnit和REST Assured ）非常容易完成。一个真实的例子值得一千个单词。

@RunWith(Arquillian.class)
@EnableRandomWebServerPort
public class PeopleApiTest {@ArquillianResource private URI uri;@Deploymentpublic static JavaArchive createArchive() {return ShrinkWrap.create(JavaArchive.class).addClasses(PeopleResource.class, PeopleApplication.class).addClasses(PeopleServiceImpl.class, PeopleJpaRepository.class, PersistenceConfig.class).addPackages(true, "org.apache.deltaspike");}@Testpublic void shouldAddNewPerson() throws Exception {final Person person = new Person("a@b.com", "John", "Smith");given().contentType(ContentType.JSON).body(person).post(uri + "/api/people").then().assertThat().statusCode(201).body("email", equalTo("a@b.com")).body("firstName", equalTo("John")).body("lastName", equalTo("Smith"));}
}

太神奇了，不是吗？它实际上是一个很大的乐趣，以发展现代的Java EE应用程序，可能有人会说了，春节的方式！实际上，与Spring的相似之处并非偶然，因为它令人鼓舞，正在鼓舞，而且无疑将继续激发Java EE生态系统中的许多创新。

未来如何？我认为，对于Jakarta EE和Eclipse Microprofile来说，绝对是光明的。后者刚刚推出了2.0版，其中包含大量新规范，旨在满足微服务架构的需求。见证这些转变的发生真是太棒了。

该项目的完整资源可在Github上找到。