Activiti 用户指南（Spring Boot集成）

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    Spring Boot集成

    根据其网站，Spring Boot是一个应用程序框架，可以轻松创建独立的、生产级的基于Spring的应用程序，你可以“just run”，大多数Spring Boot应用程序只需要很少的Spring配置。

    Spring Boot-Activiti集成目前处于试验阶段，它已经与Spring提交者一起开发，但是还处于初期。

    入门

    Spring Boot完全是关于配置的约定，首先，只需将activiti-spring-boot-starter依赖项添加到你的项目中，以Maven为例：

    <dependency>
    <groupId>org.activiti</groupId>
    <artifactId>activiti-spring-boot-starter</artifactId>
    <version>7.0.0.SR1</version>
</dependency>

    这就是所有需要的，该依赖关系将向类路径中传递正确的Activiti和Spring依赖关系，你现在可以编写Spring Boot应用程序：

    import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

@Configuration
@ComponentScan
@EnableAutoConfiguration
public class MyApplication {

    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }

}

    Activiti需要一个数据库来存储其数据，如果你运行上面的代码，它将为你提供一条提示性异常消息，你需要将数据库驱动程序依赖项添加到类路径中，现在，添加H2数据库依赖项：

    <dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
</dependency>

    现在可以启动该应用程序，你将看到如下输出：

      .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.2.RELEASE)

2019-12-19 17:19:27.564  INFO 74776 --- [           main] c.i.a.ActivitiDemoApplication            : No active profile set, falling back to default profiles: default
2019-12-19 17:19:28.929  INFO 74776 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 7000 (http)
2019-12-19 17:19:28.941  INFO 74776 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2019-12-19 17:19:28.941  INFO 74776 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.29]
2019-12-19 17:19:29.027  INFO 74776 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2019-12-19 17:19:29.027  INFO 74776 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1422 ms
2019-12-19 17:19:29.070  INFO 74776 --- [           main] .s.s.UserDetailsServiceAutoConfiguration : 
2019-12-19 17:19:33.068  INFO 74776 --- [           main] o.a.engine.impl.ProcessEngineImpl        : ProcessEngine default created
2019-12-19 17:19:33.069  INFO 74776 --- [           main] o.a.e.i.a.DefaultAsyncJobExecutor        : Starting up the default async job executor [org.activiti.spring.SpringAsyncExecutor].
2019-12-19 17:19:33.069  INFO 74776 --- [      Thread-13] o.a.e.i.a.AcquireAsyncJobsDueRunnable    : {} starting to acquire async jobs due
2019-12-19 17:19:33.069  INFO 74776 --- [      Thread-14] o.a.e.i.a.AcquireTimerJobsRunnable       : {} starting to acquire async jobs due
2019-12-19 17:19:33.070  INFO 74776 --- [      Thread-15] o.a.e.i.a.ResetExpiredJobsRunnable       : {} starting to reset expired jobs
2019-12-19 17:19:34.049  INFO 74776 --- [           main] o.s.s.web.DefaultSecurityFilterChain     : Creating filter chain: any request, [org.springframework.security.web.context.request.async.WebAsyncManagerIntegrationFilter@66e341e9, org.springframework.security.web.context.SecurityContextPersistenceFilter@28d739f1, org.springframework.security.web.header.HeaderWriterFilter@448462f0, org.springframework.security.web.csrf.CsrfFilter@55877274, org.springframework.security.web.authentication.logout.LogoutFilter@5ec9eefa, org.springframework.security.web.authentication.UsernamePasswordAuthenticationFilter@5d1bdd4a, org.springframework.security.web.authentication.ui.DefaultLoginPageGeneratingFilter@5fb3111a, org.springframework.security.web.authentication.ui.DefaultLogoutPageGeneratingFilter@5b48f0f4, org.springframework.security.web.authentication.www.BasicAuthenticationFilter@682e422c, org.springframework.security.web.savedrequest.RequestCacheAwareFilter@7e3d2ebd, org.springframework.security.web.servletapi.SecurityContextHolderAwareRequestFilter@6f50d55c, org.springframework.security.web.authentication.AnonymousAuthenticationFilter@546ed2a0, org.springframework.security.web.session.SessionManagementFilter@132e3594, org.springframework.security.web.access.ExceptionTranslationFilter@138f0661, org.springframework.security.web.access.intercept.FilterSecurityInterceptor@32ae8f27]
2019-12-19 17:19:34.098  INFO 74776 --- [           main] o.s.b.a.e.web.EndpointLinksResolver      : Exposing 2 endpoint(s) beneath base path '/actuator'
2019-12-19 17:19:34.169  INFO 74776 --- [           main] o.a.s.AbstractActivitiSmartLifeCycle     : Starting...
2019-12-19 17:19:34.193  INFO 74776 --- [           main] o.a.s.AbstractActivitiSmartLifeCycle     : Started.
2019-12-19 17:19:34.193  INFO 74776 --- [           main] o.a.s.AbstractActivitiSmartLifeCycle     : Starting...
2019-12-19 17:19:34.195  INFO 74776 --- [           main] o.a.s.AbstractActivitiSmartLifeCycle     : Started.
2019-12-19 17:19:34.248  INFO 74776 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 7000 (http) with context path ''
2019-12-19 17:19:34.251  INFO 74776 --- [           main] c.i.a.ActivitiDemoApplication            : Started ActivitiDemoApplication in 7.2 seconds (JVM running for 7.818)

    因此，仅将依赖项添加到类路径并使用@EnableAutoConfiguration注解，在幕后发生了很多事情：

    • 自动创建内存中的数据源（因为H2驱动程序在类路径中），并传递给Activiti流程引擎配置。
    • 创建并公开了一个Activiti ProcessEngine bean。
    • 所有Activiti服务都作为Spring Bean公开。
    • Spring Job Executor已创建。

    另外，processes文件夹中的任何BPMN 2.0流程定义都将自动部署，创建一个文件夹processes，然后向该文件夹添加一个虚拟流程定义（名为one-task-process.bpmn20.xml）。

    <?xml version="1.0" encoding="UTF-8"?>
<definitions
        xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL"
        xmlns:activiti="http://activiti.org/bpmn"
        targetNamespace="Examples">

    <process id="oneTaskProcess" name="The One Task Process">
        <startEvent id="theStart" />
        <sequenceFlow id="flow1" sourceRef="theStart" targetRef="theTask" />
        <userTask id="theTask" name="my task" activiti:assignee="kermit" />
        <sequenceFlow id="flow2" sourceRef="theTask" targetRef="theEnd" />
        <endEvent id="theEnd" />
    </process>

</definitions>

    还添加以下代码行以测试部署是否确实有效，CommandLineRunner是一种特殊的Spring bean，在应用程序启动时执行：

    @Configuration
@ComponentScan
@EnableAutoConfiguration
public class MyApplication {

    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }

    @Bean
    public CommandLineRunner init(final RepositoryService repositoryService,
                                  final RuntimeService runtimeService,
                                  final TaskService taskService) {

        return new CommandLineRunner() {
            @Override
            public void run(String... strings) throws Exception {
                System.out.println("Number of process definitions : "
                    + repositoryService.createProcessDefinitionQuery().count());
                System.out.println("Number of tasks : " + taskService.createTaskQuery().count());
                runtimeService.startProcessInstanceByKey("oneTaskProcess");
                System.out.println("Number of tasks after process start: " + taskService.createTaskQuery().count());
            }
        };

    }

}

    输出将如预期的那样：

    Number of process definitions : 1
Number of tasks : 0
Number of tasks after process start : 1

    更改数据库和连接池

    如上所述，Spring Boot是关于配置的约定，默认情况下，通过仅在类路径上使用H2，它创建了一个内存数据源，并将其传递给Activiti流程引擎配置。

    要更改数据源，只需提供Datasource bean即可覆盖默认值，我们在这里使用DataSourceBuilder类，它是Spring Boot的帮助类。如果在类路径上有Tomcat、HikariCP或Commons DBCP，则将选择其中之一（首先按Tomcat的顺序），例如，要切换到MySQL数据库：

    @Bean
public DataSource database() {
    return DataSourceBuilder.create()
        .url("jdbc:mysql://127.0.0.1:3306/activiti-spring-boot?characterEncoding=UTF-8")
        .username("alfresco")
        .password("alfresco")
        .driverClassName("com.mysql.jdbc.Driver")
        .build();
}

    从Maven依赖项中删除H2并将MySQL驱动程序和Tomcat连接池添加到类路径中：

    现在启动应用程序后，你会看到它使用MySQL作为数据库（和Tomcat连接池框架）：

    org.activiti.engine.impl.db.DbSqlSession   : performing create on engine with resource org/activiti/db/create/activiti.mysql.create.engine.sql
org.activiti.engine.impl.db.DbSqlSession   : performing create on history with resource org/activiti/db/create/activiti.mysql.create.history.sql
org.activiti.engine.impl.db.DbSqlSession   : performing create on identity with resource org/activiti/db/create/activiti.mysql.create.identity.sql

    多次重新启动应用程序时，你会看到任务数量增加（H2内存数据库无法在关机后生存，而MySQL可以）。

    REST支持

    通常，嵌入式Activiti引擎之上需要REST API（与公司中的不同服务进行交互），Spring Boot使这变得非常容易，将以下依赖项添加到类路径：

    <dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

    创建一个新类，一个Spring服务，并创建两个方法：一个方法启动我们的流程，另一个方法获取给定受让人的任务列表，这里仅将简单包装Activiti调用，但是在实际情况下，这显然会更加复杂。

    @Service
public class MyService {

    @Autowired
    private RuntimeService runtimeService;

    @Autowired
    private TaskService taskService;

    @Transactional
    public void startProcess() {
        runtimeService.startProcessInstanceByKey("oneTaskProcess");
    }

    @Transactional
    public List<Task> getTasks(String assignee) {
        return taskService.createTaskQuery().taskAssignee(assignee).list();
    }

}

    现在，我们可以通过使用@RestController注解类来创建REST端点，在这里，我们仅委托给上面定义的服务。

    @RestController
public class MyRestController {

    @Autowired
    private MyService myService;

    @RequestMapping(value="/process", method= RequestMethod.POST)
    public void startProcessInstance() {
        myService.startProcess();
    }

    @RequestMapping(value="/tasks", method= RequestMethod.GET, produces=MediaType.APPLICATION_JSON_VALUE)
    public List<TaskRepresentation> getTasks(@RequestParam String assignee) {
        List<Task> tasks = myService.getTasks(assignee);
        List<TaskRepresentation> dtos = new ArrayList<TaskRepresentation>();
        for (Task task : tasks) {
            dtos.add(new TaskRepresentation(task.getId(), task.getName()));
        }
        return dtos;
    }

    static class TaskRepresentation {

        private String id;
        private String name;

        public TaskRepresentation(String id, String name) {
            this.id = id;
            this.name = name;
        }

         public String getId() {
            return id;
        }
        public void setId(String id) {
            this.id = id;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }

    }

}

    我们添加到应用程序类中的自动组件扫描（@ComponentScan）都可以找到@Service和@RestController，再次运行应用程序类，现在，我们可以使用如cURL与REST API进行交互：

    curl http://localhost:8080/tasks?assignee=kermit
[]

curl -X POST  http://localhost:8080/process
curl http://localhost:8080/tasks?assignee=kermit
[{"id":"10004","name":"my task"}]
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