工作流Activiti学习二 Activiti流程引擎初始化
Activiti流程中的核心是流程引擎，其他服务都是通过ProcessEngine来获取的，获取流程引擎的同时也会初始化Activiti的原始表，下面简单介绍一下创建Activiti流程引擎的几种方式，Activiti的原始表后面再介绍。
一、pom.xml依赖
<!-- 配置版本 -->
<properties>
<sping.version>4.3.17.RELEASE</sping.version>
<mysql.version>5.1.39</mysql.version>
<activiti.version>5.22.0</activiti.version>
<mybatis.version>3.4.6</mybatis.version>
<!-- 只能使用2.0以下的版本 -->
<log4j.version>1.2.17</log4j.version>
</properties>
<dependencies>
<!-- activiti的依赖 -->
<dependency>
<groupId>org.activiti</groupId>
<artifactId>activiti-engine</artifactId>
<version>${activiti.version}</version>
</dependency>
<!-- ssm集成 -->
<dependency>
<groupId>org.activiti</groupId>
<artifactId>activiti-spring</artifactId>
<version>${activiti.version}</version>
</dependency>
<!-- mysql驱动 -->
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>${mysql.version}</version>
</dependency>
<!-- Spring相关依赖 -->
<!-- https://mvnrepository.com/artifact/org.springframework/spring-aop -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aop</artifactId>
<version>${sping.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>${sping.version}</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-aspects -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-aspects</artifactId>
<version>${sping.version}</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-context -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>${sping.version}</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-core -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${sping.version}</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-expression -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-expression</artifactId>
<version>${sping.version}</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>${sping.version}</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.springframework/spring-tx -->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-tx</artifactId>
<version>${sping.version}</version>
</dependency>
<!-- mybatis依赖 -->
<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>${mybatis.version}</version>
</dependency>
<!-- https://mvnrepository.com/artifact/log4j/log4j -->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>${log4j.version}</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.25</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-log4j12 -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.25</version>
</dependency>
</dependencies>
<build>
<plugins>
<!-- 配置编译的jdk版本 -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.7.0</version>
<configuration>
<!-- 指定source和target的版本 -->
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
二、配置数据源DataSource方式初始化Activiti原始表
import org.activiti.engine.ProcessEngine; import org.activiti.engine.ProcessEngineConfiguration; import org.activiti.engine.ProcessEngines; import org.junit.Test; import org.springframework.jdbc.datasource.DriverManagerDataSource; /** * * @ClassName: InitTable * @Description: 初始化activiti表 * @date 2020年6月25日 * */ public class InitTable { /** * 初始化方式一 * 配置数据源方式 */ @Test public void intiTables_1() { // 创建数据源 DriverManagerDataSource dataSource = new DriverManagerDataSource(); dataSource.setDriverClassName("com.mysql.jdbc.Driver"); dataSource.setUrl("jdbc:mysql://127.0.0.1:3306/activiti"); dataSource.setUsername("root"); dataSource.setPassword("123456"); // 创建流程引擎的配置 ProcessEngineConfiguration configuration = ProcessEngineConfiguration .createStandaloneProcessEngineConfiguration(); configuration.setDataSource(dataSource); // 配置初始化的方式 // DB_SCHEMA_UPDATE_FALSE：如果数据库里面没有activiti相关表，不会创建 // DB_SCHEMA_UPDATE_TRUE：如果数据库里面没有activiti相关表，创建 // DB_SCHEMA_UPDATE_CREATE_DROP：创建表，使用完成后删除 // configuration.setDatabaseSchemaUpdate(ProcessEngineConfiguration.DB_SCHEMA_UPDATE_TRUE); // drop-create：如果数据库里面有表，先删除再新建 configuration.setDatabaseSchemaUpdate("drop-create"); // 获得流程引擎 ProcessEngine processEngine = configuration.buildProcessEngine(); System.out.println(processEngine); } }
属性databaseSchemaUpdate的默认值是false。
/** Checks the version of the DB schema against the library when * the process engine is being created and throws an exception * if the versions don't match. */ public static final String DB_SCHEMA_UPDATE_FALSE = "false"; /** Upon building of the process engine, a check is performed and * an update of the schema is performed if it is necessary. */ public static final String DB_SCHEMA_UPDATE_TRUE = "true";
protected String databaseSchemaUpdate = DB_SCHEMA_UPDATE_FALSE;
databaseSchemaUpdate=‘true’： activiti会对数据库中所有表进行更新操作。如果表不存在，则自动创建。
databaseSchemaUpdate=‘false’： activiti会对数据库中表进行检测。如果表不存在，则抛出异常。默认值是false。
二、读取配置文件的方式
1、创建配置文件activiti.cfg.xml，内容如下
<?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"> <!-- 流程引擎配置--> <bean id="processEngineConfiguration" class="org.activiti.engine.impl.cfg.StandaloneProcessEngineConfiguration"> <!-- 数据库相关信息 --> <property name="jdbcUrl" value="jdbc:mysql://127.0.0.1:3306/activiti" /> <property name="jdbcDriver" value="com.mysql.jdbc.Driver" /> <property name="jdbcUsername" value="root" /> <property name="jdbcPassword" value="123456" /> <!-- 允许执行数据库更新 --> <property name="databaseSchemaUpdate" value="true" /> </bean> </beans>
2、读取配置文件的方式初始化Activiti相关表
import org.activiti.engine.ProcessEngine; import org.activiti.engine.ProcessEngineConfiguration; import org.activiti.engine.ProcessEngines; import org.junit.Test; import org.springframework.jdbc.datasource.DriverManagerDataSource; /** * * @ClassName: InitTable * @Description: 初始化activiti表 * @author xzp * @date 2020年6月25日 * */ public class InitTable { /** * 初始化方式二 * xml方式 */ @Test public void intiTables_2() { // 读取资源文件获取流程引擎配置对象 ProcessEngineConfiguration configuration = ProcessEngineConfiguration .createProcessEngineConfigurationFromResource("activiti.cfg.xml"); // 获取流程引擎 ProcessEngine processEngine = configuration.buildProcessEngine(); System.out.println(processEngine); } }
三、获取默认的流程引擎
import org.activiti.engine.ProcessEngine; import org.activiti.engine.ProcessEngineConfiguration; import org.activiti.engine.ProcessEngines; import org.junit.Test; import org.springframework.jdbc.datasource.DriverManagerDataSource; /** * * @ClassName: InitTable * @Description: 初始化activiti表 * @author * @date 2020年6月25日 * */ public class InitTable { @Test public void intiTables_3() { /** * 以这种方式创建，必须创建activiti.cfg.xml配置文件，配置文件中配置数据库、初始化方式 */ ProcessEngine processEngine = ProcessEngines.getDefaultProcessEngine(); System.out.println(processEngine); } }
我们来看下getDefaultProcessEngine做了哪些事情：
1、根据名称获流程引擎，这里是获取默认的流程引擎。判断流程引擎是否已经被初始化，如果没有被初始化，先做初始化，再从processEngines容器中获取Bean。这里ProcesssEngines是一个Map容器。
2、初始化过程
初始化大致过程：读取xml文件转化为可读资源信息，判断流程引擎信息容器中是否存在配置文件中的引擎bean信息，如果存在则移除流程引擎信息容器中bean信息，通过可读资源信息初始化流程引擎实例，并放入容器中。其实第三种方式---获取默认流程引擎是对第二种方式的封装。
/* 初始化xml文件中的所有流程引擎*/ public synchronized static void init() { if (!isInitialized()) { if(processEngines == null) { // 如果当前processEngine容器为null,创建容器用来存储流程引擎的bean processEngines = new HashMap<String, ProcessEngine>(); } // 获取类加载器 ClassLoader classLoader = ReflectUtil.getClassLoader(); Enumeration<URL> resources = null; try { // 读取xml文件资源，获取默认的流程引擎，配置文件名称必须为activiti.cfg.xml resources = classLoader.getResources("activiti.cfg.xml"); } catch (IOException e) { throw new ActivitiIllegalArgumentException("problem retrieving activiti.cfg.xml resources on the classpath: "+System.getProperty("java.class.path"), e); } // Set集合去重操作 Set<URL> configUrls = new HashSet<URL>(); while (resources.hasMoreElements()) { configUrls.add( resources.nextElement() ); } for (Iterator<URL> iterator = configUrls.iterator(); iterator.hasNext();) { URL resource = iterator.next(); log.info("Initializing process engine using configuration '{}'", resource.toString()); // 初始化流程引擎 initProcessEnginFromResource(resource); } // 通过Spring的配置初始化Activiti的流程引擎，我这个demo里并未配置 try { resources = classLoader.getResources("activiti-context.xml"); } catch (IOException e) { throw new ActivitiIllegalArgumentException("problem retrieving activiti-context.xml resources on the classpath: "+System.getProperty("java.class.path"), e); } while (resources.hasMoreElements()) { URL resource = resources.nextElement(); log.info("Initializing process engine using Spring configuration '{}'", resource.toString()); initProcessEngineFromSpringResource(resource); } setInitialized(true); } else { log.info("Process engines already initialized"); } }
initProcessEnginFromResource(resource);方法如下
private static ProcessEngineInfo initProcessEnginFromResource(URL resourceUrl) { // 获取文件中的流程引擎信息 ProcessEngineInfo processEngineInfo = processEngineInfosByResourceUrl.get(resourceUrl.toString()); // 如果流程引擎信息在容器中已经存在，则移除容器中的流程引擎信息 if (processEngineInfo!=null) { processEngineInfos.remove(processEngineInfo); if (processEngineInfo.getException()==null) { String processEngineName = processEngineInfo.getName(); processEngines.remove(processEngineName); processEngineInfosByName.remove(processEngineName); } processEngineInfosByResourceUrl.remove(processEngineInfo.getResourceUrl()); } String resourceUrlString = resourceUrl.toString(); try { log.info("initializing process engine for resource {}", resourceUrl); // 通过xml文件资源初始化流程引擎 ProcessEngine processEngine = buildProcessEngine(resourceUrl); String processEngineName = processEngine.getName(); log.info("initialised process engine {}", processEngineName); processEngineInfo = new ProcessEngineInfoImpl(processEngineName, resourceUrlString, null); // 将流程引擎实例放入流程引擎容器中 processEngines.put(processEngineName, processEngine); processEngineInfosByName.put(processEngineName, processEngineInfo); } catch (Throwable e) { log.error("Exception while initializing process engine: {}", e.getMessage(), e); processEngineInfo = new ProcessEngineInfoImpl(null, resourceUrlString, getExceptionString(e)); } processEngineInfosByResourceUrl.put(resourceUrlString, processEngineInfo); // 将流程引擎信息实例放入流程引擎信息容器中 processEngineInfos.add(processEngineInfo); return processEngineInfo; }
就罗列以上几种流程引擎初始化的方式，简单记录下，方便以后复习。
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