Activiti入门教程三（详解流程引擎配置）

               

     在先前的博客中提到了有关ProcessEngineConfiguration创建，但并没有详细的解释，主要创建的几个方法，那么这篇博客就来谈一谈有关ProcessEngineConfiguration一些创建操作。

    ProcessEngineConfiguration类

     该类代表一个Activiti流程引擎的配置，提供了一系列静态方法，用来读取和解析相应的配置文件，并返回ProcessEngineConfiguration的实例。下面来介绍一下有关创建实例的方法。

public static ProcessEngineConfiguration createProcessEngineConfigurationFromResourceDefault() {

    return createProcessEngineConfigurationFromResource("activiti.cfg.xml", "processEngineConfiguration");

  }

     正如源码所示，该方法默认读取classpath下面的activiti.cfg.xml配置文件，启动并获取名称为processEngineConfiguration的bean的实例，然后解析XML后就由spring来实例完成。

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public static ProcessEngineConfiguration createProcessEngineConfigurationFromResource(String resource) {

    return createProcessEngineConfigurationFromResource(resource, "processEngineConfiguration");

  }

     正如源码所示，该方法默认读取classpath下面指定名称的XML配置文件，关键在于传入的String类型的resource参数，跟上面类似，指定的bean的id名称为processEngineConfiguration

public static ProcessEngineConfiguration createProcessEngineConfigurationFromResource(String resource, String beanName) {

    return BeansConfigurationHelper.parseProcessEngineConfigurationFromResource(resource, beanName);

  }

     正如源码所示，读取我们自己命名的XML文件，并且bean的名称也可以由我们自己指定。例如我创建一个名称为my-activiti2.xml，里面的内容如下

<span style="font-family:Comic Sans MS;font-size:18px;"><?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans   http://www.springframework.org/schema/beans/spring-beans.xsd"> <!-- 配置自定义属性 --> <bean id="processEngineConfiguration" class="org.crazyit.activiti.MyConfiguration">  <property name="jdbcUrl" value="jdbc:mysql://localhost:3306/activiti" />  <property name="jdbcDriver" value="com.mysql.jdbc.Driver" />  <property name="jdbcUsername" value="root" />  <property name="jdbcPassword" value="" />  <property name="databaseSchemaUpdate" value="drop-create"></property>  <property name="userName" value="crazyit"></property> </bean></beans></span>

public static ProcessEngineConfiguration createProcessEngineConfigurationFromInputStream(InputStream inputStream, String beanName) {

    return BeansConfigurationHelper.parseProcessEngineConfigurationFromInputStream(inputStream, beanName);

  }

     正如源码所示，xml文件以一种输入流的形式进行输入，后面的参数就不再讲解了，不同点就是xml的读取方式变为了输入流的形式，如下

<span style="font-family:Comic Sans MS;font-size:18px;">package org.crazyit.activiti;import java.io.File;import java.io.FileInputStream;import java.io.InputStream;import java.util.Map;import org.activiti.engine.ProcessEngine;import org.activiti.engine.ProcessEngineConfiguration;import org.activiti.engine.ProcessEngines;public class CreateInputStream { public static void main(String[] args) throws Exception {  File file = new File("resource/input-stream.xml");  // 得到文件输入流  InputStream fis = new FileInputStream(file);  // 使用createProcessEngineConfigurationFromInputStream方法创建ProcessEngineConfiguration  ProcessEngineConfiguration config = ProcessEngineConfiguration    .createProcessEngineConfigurationFromInputStream(fis); }}</span>

public static ProcessEngineConfiguration createStandaloneProcessEngineConfiguration() {
    return new StandaloneProcessEngineConfiguration();
  }

     正如源码所示，这个方法过于简单，就是直接通过new来创建对象，关于数据库的一系列操作，还得通过代码手动来赋值，如下所示

<span style="font-family:Comic Sans MS;font-size:18px;">@Test public void createTable(){   ProcessEngineConfiguration configuration = ProcessEngineConfiguration.createStandaloneProcessEngineConfiguration();  //定义连接mysql数据库  configuration.setJdbcDriver("com.mysql.jdbc.Driver");  configuration.setJdbcUrl("jdbc:mysql://localhost:3306/activiti?createDatabaseIfNotExist=true&useUnicode=true&characterEncoding=utf8");  configuration.setJdbcUsername("root");  configuration.setJdbcPassword("");  /**   *    public static final String DB_SCHEMA_UPDATE_FALSE = "false";操作activiti23张表的时候，如果表不存在，就抛出异常，不能自动创建23张表       public static final String DB_SCHEMA_UPDATE_CREATE_DROP = "create-drop";每次操作，都会先删除表，再创建表        public static final String DB_SCHEMA_UPDATE_TRUE = "true";如果表不存在，就创建表，如果表存在，就直接操作   */  configuration.setDatabaseSchemaUpdate(ProcessEngineConfiguration.DB_SCHEMA_UPDATE_TRUE);  //activiti核心对象（流程引擎）  ProcessEngine processEngine = configuration.buildProcessEngine();  System.out.println("processEngine："+processEngine); }</span>

     ProcessEngineConfiguration类的结构图

    正如上图所示，ProcessEngineConfiguration是全部配置类的父类，有一个ProcessEngineConfigurationImpl子类，ProcessEngineConfigurationImpl下面有三个直接的子类，其中ProcessEngineConfiguration和ProcessEngineConfigurationImpl都是抽象类

     了解了ProcessEngineConfiguration类的结构后，我们也可以自定义属于我们自己的引擎配置，只要继承抽象类ProcessEngineConfigurationImpl即可，如下所示

<span style="font-family:Comic Sans MS;font-size:18px;">package org.crazyit.activiti;import java.util.ArrayList;import java.util.Collection;import java.util.List;import org.activiti.engine.impl.cfg.ProcessEngineConfigurationImpl;import org.activiti.engine.impl.interceptor.CommandContextInterceptor;import org.activiti.engine.impl.interceptor.CommandInterceptor;public class MyConfiguration extends ProcessEngineConfigurationImpl {  public MyConfiguration() {  // 做自定义设置 }  //测试属性，需要在processEngineConfiguration注入 private String userName;  public void setUserName(String userName) {  this.userName = userName; } public String getUserName() {  return this.userName; } //返回命令拦截器集合 protected Collection<? extends CommandInterceptor> getDefaultCommandInterceptorsTxRequired() {     List<CommandInterceptor> defaultCommandInterceptorsTxRequired = new ArrayList<CommandInterceptor>();   //定义一个拦截器，该拦截器为系统内置拦截器，用于执行SQL脚本     defaultCommandInterceptorsTxRequired.add(new CommandContextInterceptor(commandContextFactory, this));     return defaultCommandInterceptorsTxRequired; } //返回命令拦截器集合 protected Collection<? extends CommandInterceptor> getDefaultCommandInterceptorsTxRequiresNew() {  return super.commandInterceptorsTxRequired; }}</span>

           

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