用Spring构建企业Java应用程序的方法

xieed SpringForAll社区 2020-10-17

原文链接：https://dzone.com/articles/building-enterprise-java-applications-the-spring-w
作者：Andriy Redko
译者：xieed

通过在本教程中构建一个简单的RESTful web API，了解关于使用Java EE和Spring框架构建企业Java应用程序的更多信息。

我认为可以说Java EE在Java开发人员中获得了相当坏的名声。尽管多年来，它确实在各个方面都有所改善，甚至从Eclipse Foundation变成了JakartaEE，但它的苦味仍然相当强烈。另一方面，我们有Spring Framework(或者更好地反映现实，一个成熟的Spring Platform)，这是一个出色的、轻量级的、快速的、创新的、高生产力的Java EE替代品。那么，为什么要为Java EE费心呢?我们将通过展示使用大多数Java EE规范构建现代Java应用程序是多么容易来回答这个问题。在这方面取得成功的关键因素是Eclipse Microprofile:J2EE的微服务时代。我们将要构建的应用程序是用于管理人员的RESTful web API;就这么简单。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)将负责数据访问层。当然，Bean Validation 2.0 (JSR-380)正在帮助我们处理输入验证。我们唯一要依赖的非java EE规范是OpenAPI v3.0，它有助于提供关于RESTful web api的可用描述。那么，让我们从personentity域模型开始(省略getter和setter作为不太相关的细节):

@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;
@Version
private Long version;
}

它只有一个绝对最小的属性集。JPA存储库非常简单，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
@Transactional
public 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
@Transactional
public Optional<PersonEntity> deleteByEmail(String email) {
return findByEmail(email)
.map(entity -> {
em.remove(entity);
return entity;
});
}
}

事务管理(即@Transactionalannotation)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。由于我们不想装载应用程序容器，而是保持精简，所以我们可以使用EntityManager来启动/提交/回滚事务。这当然是可行的，但它也会用样板污染代码。可以说，更好的选择是使用Apache DeltaSpikeCDI扩展用于声明性事务管理(这是@Transactional和@EntityManagerConfig注释的来源)。下面的代码片段说明了如何集成它。

@ApplicationScoped
public class PersistenceConfig {
@PersistenceUnit(unitName = "peopledb")
private EntityManagerFactory entityManagerFactory;
@Produces @PeopleDb @TransactionScoped
public 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person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。但总的来说，这不是一个很好的实践，所以让我们介绍PeopleServiceImpl。

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

没什么好说的;这是尽可能简单的。但是JAX-RS资源实现更有趣(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"));
}
}

这样，我们就完成了!但是，我们怎样才能把这些零件组装起来，然后用电线把它们连在一起呢?现在是 Microprofile进入舞台的时候了。有许多实现可供选择;我们将在这篇文章中使用的是Project Hammock 。我们要做的唯一一件事就是指定我们想要使用的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)。让我们来看看Apache Mavenpom.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>

在没有进一步的ado的情况下，让我们立即构建和运行应用程序(如果您想知道应用程序使用的是什么关系数据存储，那么它是H2，在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RESTful web api功能完备的最佳方法是向它发送几个请求:

> 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 Validation 工作正常?为了触发它，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

OpenAPI规范和预捆绑的Swagger UI发行版也可以通过http://localhost:10900/index.html?url=http://localhost:10900/api/openapi.json获得。到目前为止，一切都很好，但公平地说，我们根本没有谈到测试我们的应用程序。要为添加一个person的场景设计出集成测试有多难呢?事实证明，围绕Java EE应用程序测试的框架已经有了很大的改进。特别是，使用Arquillian测试框架(以及受欢迎的JUnit和REST Assured)非常容易完成。一个真实的例子抵得上千言万语。

@RunWith(Arquillian.class)
@EnableRandomWebServerPort
public class PeopleApiTest {
@ArquillianResource private URI uri;
@Deployment
public 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");
}
@Test
public 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"));
}
}

不神奇吗?实际上，开发现代Java EE应用程序是非常有趣的，有人可能会说，用Spring的方式!事实上，与Spring的相似之处并非巧合，因为它很有启发性，很有启发性，而且无疑将继续激励Java EE生态系统中的创新。未来如何?我认为，无论对于雅加达EE还是Eclipse Microprofile来说，都是光明的。后者刚刚接近2.0版本，提供了大量新的规范，这些规范旨在满足微服务体系结构的需求。目睹这些转变真是太棒了。项目的完整源代码可以在GitHub上找到。

推荐：【SFA官方译】：使用Spring Security保护REST API

上一篇：持久化DDD聚合

关注公众号

点击原文查看更多

喜欢此内容的人还喜欢

反向激励，在加速这个社会的黑化

把抄袭说的如此冠冕堂皇，雷军让年轻人丢掉了耻辱感

2024【公共营养师】报名通道已开启，不限学历，23岁及以上可报!还能领2000补贴

Wealth | 中国成本轮金价涨势的前沿和中心

父亲出轨后，母亲对父亲实施了她的精确打击 | 二湘空间