In -depth understanding of Spring Web Flow's status machine model
In -depth understanding of Spring Web Flow's status machine model
Summary: Spring Web Flow is a Java -based open source framework that is used to develop a process -based web application.This article will explore the status model of the Spring Web Flow, introduce its core concepts and usage, and use the Java code example to demonstrate how to use the status machine model to build a complex web application.
1 Introduction
Spring Web Flow is a module provided by the Spring framework to simplify process control and navigation management in Web applications.It is based on the state model and modeling the state of the application and the transformation of the application to achieve flexible process control and navigation management functions.
2. State machine model basics
In Spring Web Flow, the state machine model consists of state, transition, and behavior.
2.1 Status (State)
The state is the state where the application is at any time.In the state machine model, the state can include pages, processes and sub -processes.Each state has a unique identifier, and can define related behavior and conversion.
2.2 Transition
Conversion is a switching action between state.One conversion can have multiple trigger events, each event is associated with an execution action (Action).When an event is triggered, the system will determine whether the conversion can be executed according to the defined conditions. If the conditions are met, the current state is switched to the target state.
2.3 Action (ACTION)
Behavior is a specific operation related to conversion.In Spring Web Flow, behavior can be a method, an expression, or a processor of a specific event.Actions can be performed during conversion, such as updating databases, computing formulas and other operations.
3. The status machine model in Spring Web Flow
In Spring Web Flow, the state machine model can be defined by configuration files (Flow.xml) or Java code.
3.1 Configuration file method
The following is a simple Flow.xml configuration file example:
<flow xmlns="http://www.springframework.org/schema/webflow"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/webflow http://www.springframework.org/schema/webflow/spring-webflow.xsd">
<view-state id="login" view="login.html">
<transition on="submit" to="home">
<evaluate expression="userDAO.validate(credentials)"/>
</transition>
</view-state>
<view-state id="home" view="home.html">
<!-Other conversions between state->
</view-state>
</flow>
The above configuration files define two states, login and home.The login state is a view state, which corresponds to a view called login.html.The login state defines a conversion event called Submit, and an method call is executed when the conversion occurs.
3.2 Java code method
In addition to the configuration file, Spring Web Flow can also use Java code to define the state machine model.The following is an example:
@Configuration
@EnableWebMvc
public class WebFlowConfig extends AbstractFlowConfiguration {
@Autowired
private UserDAO userDAO;
@Bean
public FlowHandlerMapping flowHandlerMapping() {
FlowHandlerMapping handlerMapping = new FlowHandlerMapping();
handlerMapping.setFlowRegistry(flowRegistry());
return handlerMapping;
}
@Bean
public FlowExecutor flowExecutor() {
return getFlowExecutorBuilder(flowRegistry()).build();
}
@Bean
public FlowDefinitionRegistry flowRegistry() {
DefaultFlowDefinitionRegistry registry = new DefaultFlowDefinitionRegistry();
registry.addFlowDefinition(flowBuilderServices().getFlowBuilder(flowId(), flowBuilder()).build());
return registry;
}
@Bean
public FlowBuilderServices flowBuilderServices() {
return getFlowBuilderServicesBuilder().setViewFactoryCreator(mvcViewFactoryCreator())
.setExpressionParser(expressionParser())
.setConversionService(conversionService())
.setDevelopmentMode(true)
.build();
}
@Bean
public ViewFactoryCreator mvcViewFactoryCreator() {
return new MvcViewFactoryCreator();
}
@Bean
public ExpressionParser expressionParser() {
return new SpelExpressionParser();
}
@Bean
public ConversionService conversionService() {
return new DefaultConversionService();
}
public FlowBuilder flowBuilder() {
return new FlowBuilder(flowId()) {
public void buildStates() throws FlowBuilderException {
ViewStateBuilder loginState = viewState("login", "login.html");
loginState.transition(on("submit"), to("home"), evaluate("userDAO.validate(credentials)"));
ViewStateBuilder homeState = viewState("home", "home.html");
// Other conversion between state
}
};
}
public String flowId() {
return "myFlow";
}
}
The above example uses Spring's Java configuration method to define the state machine model. It is defined by annotations and bean to build a FlowController, a FlowExecutor, and a FlowDefinitionRegatory and other components, and then programmed by programming.Define status, conversion and behavior.
4. Summary
This article introduces the status model of Spring Web Flow, and provides corresponding examples through configuration files and Java code.This state machine model can help developers better understand and apply the Spring Web Flow framework to achieve complex web application process control and navigation management.
