Activiti入門教程三（詳解流程引擎配置）
在先前的部落格中提到了有關ProcessEngineConfiguration建立，但並沒有詳細的解釋，主要建立的幾個方法，那麼這篇部落格就來談一談有關ProcessEngineConfiguration一些建立操作。
ProcessEngineConfiguration類
該類代表一個Activiti流程引擎的配置，提供了一系列靜態方法，用來讀取和解析相應的配置檔案，並返回ProcessEngineConfiguration的例項。下面來介紹一下有關建立例項的方法。
public static ProcessEngineConfiguration createProcessEngineConfigurationFromResourceDefault() {
return createProcessEngineConfigurationFromResource("activiti.cfg.xml", "processEngineConfiguration");
}
正如原始碼所示，該方法預設讀取classpath下面的activiti.cfg.xml配置檔案，啟動並獲取名稱為processEngineConfiguration的bean的例項，然後解析XML後就由spring來例項完成。
public static ProcessEngineConfiguration createProcessEngineConfigurationFromResource(String resource) {
return createProcessEngineConfigurationFromResource(resource, "processEngineConfiguration");
}
正如原始碼所示，該方法預設讀取classpath下面指定名稱的XML配置檔案，關鍵在於傳入的String型別的resource引數，跟上面類似，指定的bean的id名稱為processEngineConfiguration
public static ProcessEngineConfiguration createProcessEngineConfigurationFromResource(String resource, String beanName) {
return BeansConfigurationHelper.parseProcessEngineConfigurationFromResource(resource, beanName);
}
正如原始碼所示，讀取我們自己命名的XML檔案，並且bean的名稱也可以由我們自己指定。例如我建立一個名稱為my-activiti2.xml，裡面的內容如下
<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">
<!-- 配置自定義屬性 -->
<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);
}
正如原始碼所示，xml檔案以一種輸入流的形式進行輸入，後面的引數就不再講解了，不同點就是xml的讀取方式變為了輸入流的形式，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");
// 得到檔案輸入流
InputStream fis = new FileInputStream(file);
// 使用createProcessEngineConfigurationFromInputStream方法建立ProcessEngineConfiguration
ProcessEngineConfiguration config = ProcessEngineConfiguration
.createProcessEngineConfigurationFromInputStream(fis);
}
}</span>public static ProcessEngineConfiguration createStandaloneProcessEngineConfiguration() {
return new StandaloneProcessEngineConfiguration();
}
正如原始碼所示，這個方法過於簡單，就是直接通過new來建立物件，關於資料庫的一系列操作，還得通過程式碼手動來賦值，如下所示
<span style="font-family:Comic Sans MS;font-size:18px;">@Test
public void createTable(){
ProcessEngineConfiguration configuration = ProcessEngineConfiguration.createStandaloneProcessEngineConfiguration();
//定義連線mysql資料庫
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張表的時候，如果表不存在，就丟擲異常，不能自動建立23張表
public static final String DB_SCHEMA_UPDATE_CREATE_DROP = "create-drop";每次操作，都會先刪除表，再建立表
public static final String DB_SCHEMA_UPDATE_TRUE = "true";如果表不存在，就建立表，如果表存在，就直接操作
*/
configuration.setDatabaseSchemaUpdate(ProcessEngineConfiguration.DB_SCHEMA_UPDATE_TRUE);
//activiti核心物件（流程引擎）
ProcessEngine processEngine = configuration.buildProcessEngine();
System.out.println("processEngine："+processEngine);
}</span>ProcessEngineConfiguration類的結構圖
正如上圖所示，ProcessEngineConfiguration是全部配置類的父類，有一個ProcessEngineConfigurationImpl子類，ProcessEngineConfigurationImpl下面有三個直接的子類，其中ProcessEngineConfiguration和ProcessEngineConfigurationImpl都是抽象類
瞭解了ProcessEngineConfiguration類的結構後，我們也可以自定義屬於我們自己的引擎配置，只要繼承抽象類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() {
// 做自定義設定
}
//測試屬性，需要在processEngineConfiguration注入
private String userName;
public void setUserName(String userName) {
this.userName = userName;
}
public String getUserName() {
return this.userName;
}
//返回命令攔截器集合
protected Collection<? extends CommandInterceptor> getDefaultCommandInterceptorsTxRequired() {
List<CommandInterceptor> defaultCommandInterceptorsTxRequired = new ArrayList<CommandInterceptor>();
//定義一個攔截器，該攔截器為系統內建攔截器，用於執行SQL指令碼
defaultCommandInterceptorsTxRequired.add(new CommandContextInterceptor(commandContextFactory, this));
return defaultCommandInterceptorsTxRequired;
}
//返回命令攔截器集合
protected Collection<? extends CommandInterceptor> getDefaultCommandInterceptorsTxRequiresNew() {
return super.commandInterceptorsTxRequired;
}
}
</span>