说说如何在项目中引入 jBPM4 工作流框架以及遇到的坑儿

由于各种原因，我们需要在项目中引入 jBPM4 工作流框架，遇到了不少问题，今记录如下O(∩_∩)O

1 引入步骤

1.1 加入依赖包

1. 非 Maven 项目，在 lib 包中加入 jbpm.jar。
2. Maven 项目，加入以下配置：

	org.jbpm
	jbpm
	${jbpm.version}

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如果私服上没有，可以自行作为第三方库上传到私服后，再配置 pom.xml。

1.2 集成到 Spring

"springHelper" class="org.jbpm.pvm.internal.processengine.SpringHelper"
	  lazy-init="default" autowire="default">
	"jbpmCfg">
		jbpm.cfg.xml
	



"processEngine" factory-bean="springHelper"
	  factory-method="createProcessEngine"/>
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名为 springHelper 的 Bean 中可以配置一个 jbpmCfg 参数，用于自定义 jbpm 配置文件。该文件名为 jbpm.cfg.xml，默认放置在 classpath 路径下。

1.3 配置 Hibernate

因为 jBPM4 使用的是 Hibernate 进行持久化操作，所以我们必须在此配置 jBPM4 持久化映射文件：

"sessionFactory"
	class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
	"dataSource" ref="dataSource" />
	"hibernateProperties">
		
			"hibernate.dialect">${hibernate.dialect}
			"hibernate.hbm2ddl.auto">${hibernate.hbm2ddl.auto}
			"hibernate.show_sql">${hibernate.show_sql}
			"hibernate.format_sql">${hibernate.format_sql}
			"hibernate.temp.use_jdbc_metadata_defaults">${hibernate.temp.use_jdbc_metadata_defaults}
		
	
	...

	
	"mappingResources">
		
			jbpm.repository.hbm.xml
			jbpm.execution.hbm.xml
			jbpm.history.hbm.xml
			jbpm.task.hbm.xml
			jbpm.identity.hbm.xml
		
	

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一般来说，通过以上步骤就可以通过注入，获取到 jBPM4 的 processEngine 引擎啦O(∩_∩)O哈哈~

1.4 执行脚本

在下载的 jbpm-4.4 包中，打开 install\jdbc\ 文件夹，依据实际的数据库类型，选择相应的脚本，初始化 jBPM 库表：

2 兼容 Hibernate4+

jBPM4 默认适配 Hibernate3，所以如果框架使用的是高版本的 Hibernate，那么就必须修改 jBPM4 的源代码做适配。

下面以 Hibernate4 为例，我们需要修改 jBPM4 这 SpringProcessEngine 与 HibernateSessionDescriptor 两个类。

修改后的 jBPM4 源代码如下：

1、SpringProcessEngine.java

public class SpringProcessEngine extends ProcessEngineImpl {

  private static final Log log = Log.getLog(SpringProcessEngine.class.getName());

  private static final long serialVersionUID = 1L;

  private ApplicationContext applicationContext;

  public static ProcessEngine create(ConfigurationImpl configuration) {
    SpringProcessEngine springProcessEngine = null;

    ApplicationContext applicationContext = null;
    if (configuration.isInstantiatedFromSpring()) {
      applicationContext = (ApplicationContext) configuration.getApplicationContext();

      springProcessEngine = new SpringProcessEngine();
      springProcessEngine.applicationContext = applicationContext;
      springProcessEngine.initializeProcessEngine(configuration);

      LocalSessionFactoryBean localSessionFactoryBean = springProcessEngine.get(LocalSessionFactoryBean.class);
      Configuration hibernateConfiguration = localSessionFactoryBean.getConfiguration();
      springProcessEngine.processEngineWireContext
          .getWireDefinition()
          .addDescriptor(new ProvidedObjectDescriptor(hibernateConfiguration, true));

      springProcessEngine.checkDb(configuration);

    } else {
      String springCfg = (String) configuration.getProcessEngineWireContext().get("spring.cfg");
      if (springCfg==null) {
        springCfg = "applicationContext.xml";
      }
      applicationContext = new ClassPathXmlApplicationContext(springCfg);
      springProcessEngine = (SpringProcessEngine) applicationContext.getBean
              ("jbpmProcessEngine");
    }

    return springProcessEngine;
  }

  public EnvironmentImpl openEnvironment() {
    PvmEnvironment environment = new PvmEnvironment(this);

    if (log.isTraceEnabled())
      log.trace("opening jbpm-spring" + environment);

    environment.setContext(new SpringContext(applicationContext));

    installAuthenticatedUserId(environment);
    installProcessEngineContext(environment);
    installTransactionContext(environment);

    return environment;
  }

  @SuppressWarnings("unchecked")
  @Override
  public  T get(Class type) {
    T candidateComponent = super.get(type);

    if (candidateComponent != null) {
      return candidateComponent;
    }

    String[] names = applicationContext.getBeanNamesForType(type);

    if (names.length >= 1) {

      if (names.length > 1 && log.isWarnEnabled()) {
        log.warn("Multiple beans for type " + type + " found. Returning the first result.");
      }

      return (T) applicationContext.getBean(names[0]);
    }

    return null;
  }

  @Override
  public Object get(String key) {
    if (applicationContext.containsBean(key)) {
      return applicationContext.getBean(key);
    }

    return super.get(key);
  }
}
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2、HibernateSessionDescriptor.java

public class HibernateSessionDescriptor extends AbstractDescriptor {

    private static final long serialVersionUID = 1L;
    private static final Log log = Log.getLog(HibernateSessionDescriptor.class.getName());

    protected String factoryName;
    protected boolean useCurrent = false;
    protected boolean tx = true;
    protected boolean close = true;
    protected String standardTransactionName;
    protected String connectionName;

    public Object construct(WireContext wireContext) {
        EnvironmentImpl environment = EnvironmentImpl.getCurrent();
        if (environment == null) {
            throw new WireException("no environment");
        }

        // get the hibernate-session-factory
        SessionFactory sessionFactory = null;
        if (factoryName != null) {
            sessionFactory = (SessionFactory) wireContext.get(factoryName);
        } else {
            sessionFactory = environment.get(SessionFactory.class);
        }
        if (sessionFactory == null) {
            throw new WireException("couldn't find hibernate-session-factory " + (factoryName != null ? "'" + factoryName + "'" : "by type ") + "to open a hibernate-session");
        }

        // open the hibernate-session
        Session session = null;
        if (useCurrent) {
            if (log.isTraceEnabled()) log.trace("getting current hibernate session");
            session = sessionFactory.getCurrentSession();

        } else if (connectionName != null) {
            Connection connection = (Connection) wireContext.get(connectionName);
            if (log.isTraceEnabled())
                log.trace("creating hibernate session with connection " + connection);
            session = (Session)sessionFactory.openStatelessSession(connection);
        } else {
            if (log.isTraceEnabled()) log.trace("creating hibernate session");
            session = sessionFactory.openSession();
        }

        StandardTransaction standardTransaction = environment.get(StandardTransaction.class);
        if (standardTransaction != null) {
            HibernateSessionResource hibernateSessionResource = new HibernateSessionResource(session);
            standardTransaction.enlistResource(hibernateSessionResource);
        }

        return session;
    }

    public Class getType(WireDefinition wireDefinition) {
        return SessionImpl.class;
    }

    public void setFactoryName(String factoryName) {
        this.factoryName = factoryName;
    }

    public void setTx(boolean tx) {
        this.tx = tx;
    }

    public void setStandardTransactionName(String standardTransactionName) {
        this.standardTransactionName = standardTransactionName;
    }

    public void setConnectionName(String connectionName) {
        this.connectionName = connectionName;
    }

    public void setUseCurrent(boolean useCurrent) {
        this.useCurrent = useCurrent;
    }

    public void setClose(boolean close) {
        this.close = close;
    }
}
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3 兼容 Activiti5+

你没有看错，有的项目就是这么奇葩，已经有 Activiti5 咯，还需要集成进 jBPM4……

这两套框架都是同一个架构师 Tom Baeyens 负责的，可谓是一脉相承，所以一些基本 Bean 的命名都是相同的，比如流程引擎 Bean 都叫做 processEngine。因此如果直接按照上述配置，就会出现 Spring Bean 命名冲突的问题。

1、重命名 jBPM 工作流引擎 Bean

"jbpmProcessEngine" factory-bean="jbpmSpringHelper"
	  factory-method="createProcessEngine"/>
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2、在 注入时使用该名称（比如这里取名为 jbpmProcessEngine）

4 非 Spring 环境

是的，有的项目非常老，连 Spring 框架都没有用，纳尼……

可以写一个工具类，把流程引擎对象作为常量返回：

public class WorkflowUtils {


    //工作流引擎
    private static ProcessEngine PROCESS_ENGINE;
	
	//配置文件前缀
    public static final String SPRING_CONFIG_PREFIX = "classpath:resources/";


    /**
     * 获取工作流引擎
     *
     * @return
     */
    public static ProcessEngine getProcessEngine() {
        if (PROCESS_ENGINE == null) {
            ApplicationContext applicationContext = new ClassPathXmlApplicationContext
                    (SPRING_CONFIG_PREFIX + "spring-hibernate.xml",
                            SPRING_CONFIG_PREFIX + "spring-jbpm" +
                                    ".xml");

            PROCESS_ENGINE = (ProcessEngine) applicationContext.getBean
                    ("jbpmProcessEngine");
        }
        return PROCESS_ENGINE;
    }
}
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在此，我们利用 ApplicationContext 加载与 jBPM4 相关的配置文件，然后初始化 ProcessEngine，并设置为常量。这样，以后直接使用这个常量引擎对象就可以啦O(∩_∩)O哈哈~

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只要有耐心、细心和恒心，没有我们程序员解决不了的事儿O(∩_∩)O哈哈~