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492 строки
13 KiB
Plaintext
492 строки
13 KiB
Plaintext
https://docs.spring.io/spring/docs/current/spring-framework-reference/core.html#beans-factory-scopes
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2023
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https://www.baeldung.com/spring-bean-scopes
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Scope iface
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Creating custom scope
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Threading scopes
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public class MyScope implements Scope {
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@Override
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public Object get(String name, ObjectFactory<?> objectFactory) {
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}
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@Override
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public Object remove(String name) {
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}
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@Override
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public void registerDestructionCallback(String name, Runable callback) {
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}
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@Override
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public Object resolveContextualObject(String key) {
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}
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@Override
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public String getConversationId() {
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}
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}
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// Singleton
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private Map<String, Object> singletons = new ConcurrentHashMap<>();
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@Override
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public Object get(String name, ObjectFactory<?> objectFactory) {
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Object result = singletons.get(name)
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if (result == null) {
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result = objectFactory.getObject();
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singletons.put(name, result);
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}
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return result;
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}
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// Prototype
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@Override
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public Object get(String name, ObjectFactory<?> objectFactory) {
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return objectFactory.getObject();
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}
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They could look like this. But there is no actual implementation for those scopes.
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// Custom Scope implementation
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public class CustomScope implements Scope {
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private Map<String, Object> storage = new ConcurrentHashMap<String, Object>();
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@Override
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public Object get(String name, ObjectFactory<?> objectFactory) {
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Object object = storage.get(name);
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if (object == null) {
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object = objectFactory.getObject();
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storage.put(name, object);
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}
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return object;
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}
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@Override
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public Object remove(String name) {
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return storage.remove(name);
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}
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...
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}
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@Configuration
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public class CustomScopeConfig {
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@Bean
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public CustomScope customScope() {
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return new CustomScope();
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}
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@Bean
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public CustomScopeConfigurer customScopeConfigurer(CustomScope customScope) { // ? CustomScopeConfigurer is a native Spring ?
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CustomScopeConfigurer configurer = new CustomScopeConfigurer();
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Map<String, Object> scopes = Maps.newHashMap();
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scopes.put("custom", customScope);
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configurer.setScopes(scopes);
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return configurer;
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}
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@Bean
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@Scope("custom")
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public Logger logger() {
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return new Logger();
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}
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}
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// 2-nd way to do this:
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ConfigurableListableBeanFactory::registerScope
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// Runner
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ApplicationContext ctx = new AnnotationConfigApplicationContext(CustomScopeConfig.class);
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Logger logger = ctx.getBean(Logger.class);
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System.out.println(logger);
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CustomScope customScope = ctx.getBean(CustomScope.class);
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customScope.remove(logger);
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logger = ctx.getBean(Logger.class);
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System.out.println(logger);
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// Output
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...scopes.entity.Logger@6a472554
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...scopes.entity.Logger@7ff2a664
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// Problem
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What about injection? We need proxy!
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What about handling multiple beans of the same scope?
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// 1-st problem solution is simple:
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// Config
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@Bean
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@Scope(value="custom", proxyMode=ScopedProxyMode.TARGET_CLASS)
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public Logger logger() {
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return new Logger();
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}
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// Runner
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ApplicationContext ctx = new AnnotationConfigApplicationContext(CustomScopeConfig2.class);
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Logger logger = ctx.getBean(Logger.class);
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System.out.println(logger);
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System.out.println(logger.getClass());
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// Output
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...scopes.entity.Logger@184cf7cf
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class ...scopes.entity.Logger$$EnhancerBySpringCGLIB$$103d1ffd
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Now proxying will be handled by CGLib (which is able to override classes and not only interfaces)
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(JDK can only create proxy for i-faces)
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// 2-nd problem solution:
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public class ScopeWrapper implements BeanFactoryPostProcessor {
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private Scope scope;
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private String scopeName;
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private List<String> scopeBeanDefinitions;
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public ScopeWrapper(Scope scope, String scopeName) {
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this.scope = scope;
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this.scopeName = scopeName;
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}
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@Override
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public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
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scopeBeanDefinitions = Lists.newArrayList(beanFactory.getBeanDefinitionNames()).stream()
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.filter(beanDefinitionName -> {
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BeanDefinition beanDefinition = beanFactory.getBeanDefinition(beanDefinitionName);
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return scopeName.equals(beanDefinition.getScope());
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})
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.collect(Collectors.toList());
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}
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public void clear() {
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for (String beanDefinitionName : scopeBeanDefinitions) {
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scope.remove(beanDefinitionName);
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}
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}
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}
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@Configuration
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public class ScopeWrapperConfig {
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public CustomScope customScope() {...}
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public ScopeWrapper customScopeWrapper(CustomScope customScope) {...}
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public CustomScopeConfigurer simpleThreadScopeConfigurer(CustomScope customScope) {...}
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public Logger logger() {...}
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public Service service() {...}
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}
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// Runner
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ApplicationContext ctx = new AnnotationConfigApplicationContext(ScopeWrapperConfig.class);
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Logger logger = ctx.getBean(Logger.class);
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System.out.println(logger);
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Service service = ctx.getBean(Service.class);
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System.out.println(service);
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ScopeWrapper scopeWrapper = ctx.getBean(ScopeWrapper.class);
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scopeWrapper.clear();
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logger = ctx.getBean(Logger.class);
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System.out.println(logger);
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service = ctx.getBean(Service.class);
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System.out.println(service);
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// Output
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...scopes.entity.Logger@5762806e
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...scopes.entity.Service@17c386de
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...scopes.entity.Logger@5af97850
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...scopes.entity.Service@5ef60048
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// Problem
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I have http-interface application. And it's multithreaded. I need the Request scope.
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/// org.springframework.context.support.SimpleThreadScope
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private final ThreadLocal<Map<String, Object>> threadScope =
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new NamedThreadLocal<Map<String, Object>>("SimpleThreadScope") {
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@Override
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protected Map<String, Object> initialValue() {
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return new HashMap<String, Object>();
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}
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}
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@Override
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public Object get(String name, ObjectFactory<?> objectFactory) {
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Map<String, Object> scope = this.threadScope.get();
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Object object = scope.get(name);
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if (object == null) {
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object = objectFactory.getObject();
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scope.put(name, object);
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}
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return object;
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}
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@Override
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public Object remove(String name) {
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Map<String, Object> scope = this.threadScope.get();
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return scope.remove(name);
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}
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// 1. get() - populates bean in ThreadLocal map
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// 2. remove() - removes bean from ThreadLocal map
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// Thread scope logging
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// Model
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public class Logger {
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private List<String> events;
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public Logger() {
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this.events = Lists.newArrayList();
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}
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public void addEvent(String event) {
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this.events.add(event);
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}
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public List<String> getEvents() {
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return this.events;
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}
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}
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// Config
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@Configuration
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public class SimpleThreadScopeConfig {
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@Bean
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public SimpleThreadScope simpleThreadScope() {
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return new SimpleThreadScope();
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}
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@Bean
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public CustomScopeConfigurer simpleThreadScopeConfigurer(SimpleThreadScope simpleThreadScope) {
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CustomScopeConfigurer configurer = new CustomScopeConfigurer();
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Map <String, Object> scopes = Maps.newHashMap();
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scopes.put("thread", simpleThreadScope);
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configurer.setScope(scopes)
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return configurer;
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}
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@Bean
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@Scope(value="thread", proxyMode=ScopedProxyMode.TARGET_CLASS)
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public Logger logger() {
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return new Logger();
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}
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}
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// Runner
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ApplicationContext ctx = new AnnotationConfigApplicationContext(SimpleThreadScopeConfig.class);
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Runnable r = () -> {
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Logger logger = ctx.getBean(Logger.class);
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logger.addEvent("Hello, i'm thread " + Thread.currentThread().getId());
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System.out.println(logger.getEvents());
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};
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new Thread(r).start();
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new Thread(r).start();
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// Output
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[Hello, i'm thread 12]
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[Hello, i'm thread 11]
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// Problem
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What about thread pools???
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// Thread pool and thread scope
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// Runner
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ApplicationContext ctx = new AnnotationConfigApplicationContext(SimpleThreadScopeConfig.class);
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Runnable r = () -> {
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Logger logger = ctx.getBean(Logger.class);
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logger.addEvent("Hello, i'm thread " + Thread.currentThread().getId());
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};
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ExecutorService executor = Executors.newSingleThreadExecutor();
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executor.execute(r);
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executor.shutdown();
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executor.awaitTermination(10, TimeUnit.SECONDS);
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System.out.println(ctx.getBean(Logger.class).getEvents());
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// Output
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[]
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// Problem
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Thread pool thread is not associated with the current thread.
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// Wrap Runnable and Callable
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private Callable<?> wrapCallable(Callable<?> callable) {
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Map<String, Object> callingThreadContext = scope.getCurrentThreadContext();
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return () -> {
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scope.replaceContext(callingThreadContext);
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try {
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return callable.call();
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} finally {
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scope.removeContext();
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}
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}
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}
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private Runnable wrapRunnable(Runnable runnable) {
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Map<String, Object> callingThreadContext = scope.getCurrentThreadContext();
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return () -> {
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scope.replaceContext(callingThreadContext);
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try {
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return runnable.run();
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} finally {
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scope.removeContext();
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}
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}
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}
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// from the Spring src:
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public void replaceContext(Map<Spring, Object> context) {
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this.threadScope.set(context);
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}
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public void removeContext() {
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this.threadScope.remove();
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}
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public Map<String, Object> getCurrentThreadContext() {
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return this.threadScope.get();
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}
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// AssociatableExecutorFactory
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@SuppressWarnings({"rawtypes", "unchecked"})
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public ExecutorService wrap(ExecutorService executor) {
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//
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// 1. Proxying ExecutorService
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//
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return (ExecutorService) Proxy.newProxyInstance(
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ExecutorService.class.getClassLoader(),
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new Class[] { ExecutorService.class },
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new InvocationHandler() {
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@Override
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public Object invoke(Object proxy, Method method, Object [] args) throws Throwable {
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if (args != null) {
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//
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// 2. Iterate over the arguments of the method call
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//
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for (int i = 0; i < args.length; ++i) {
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//
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// 3. Wrap collection or single object
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//
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if (Collection.class.isAssibnableFrom(arg.getClass())) {
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args[i] = ((Collection) arg).stream().map((listItem) -> {
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return tryToWrapSingleObject(listItem);
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})
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.collect(Collectors.toList());
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} else {
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args[i] = tryToWrapSingleObject(arg);
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}
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}
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}
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return method.invoke(executor, args);
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}
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private Object tryToWrapSingleObject(Object arg) {
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if (Callable.class.isAssignableFrom(arg.getClass())) {
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return wrapCallable((Callable) arg);
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} else if (Runnable.class.isAssignableFrom(arg.getClass())) {
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return wrapRunnable((Runnable) arg);
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} else {
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return arg;
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}
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}
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private Callable<?> wrapCallable(Callable<?> callable) { ... }
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private Runnable wrapRunnable(Runnable runnable) { ... }
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}
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);
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}
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// Thread pool and thread scope
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// Runner
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ApplicationContext ctx = new AnnotationConfigApplicationContext(AssociatableThreadScopeConfig.class);
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Runnable r = () -> {
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Logger logger = ctx.getBean(Logger.class);
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logger.addEvent("Hello, i'm thread " + Thread.currentThread().getId());
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};
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AssociatableExecutorFactory executorFactory = ctx.getBean(AssociatableExecutorFactory.class);
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ExecutorService executor = executorFactory.wrap(Executors.newSingleThreadExecutor());
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executor.execute(r);
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executor.shutdown();
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executor.awaitTermination(10, TimeUnit.SECONDS);
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System.out.println(ctx.getBean(Logger.class).getEvents());
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// Output
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[Hello, i'm thread 11]
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Current thread is 1
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// Readl HTTP server application case
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//
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// 1. Define scope
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//
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@Configuration
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private static class Config {
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@Bean @Scope("request") public Logger logger() ...
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@Bean public RequestScope requestScope() ...
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@Bean CustomScopeConfigurere requestScope() ...
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...
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}
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//
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// 2. Create request filter
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//
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private static class RequestFilter {
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@Autowired
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private ScopeWrapper requestScopeWrapper;
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public void filterRequest(Object request) {
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requestScopeWrapper.clear();
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requestScopeWrapper.getScope().put("request", request);
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}
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}
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//
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// 3. Create response filter
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//
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private static class ResponseFilter {
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@Autowired
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private Logger logger;
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@Autowired
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private Object request; // this will be proxy
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public void filterResponse(Object response) {
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System.out.println(logger.getEvents());
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}
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}
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//
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// 4. Inject your "request" scope bean
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//
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private static class UserService {
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@Autowired
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private Logger logger; // this will be proxy
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public void registerUser(Object user) {
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// login
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logger.addEvent("User " + user + " was registered.");
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}
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}
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// Conclusion
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1. Custom scopes are needed to modify bean lifetime
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2. Always think about concurrency, when creating custom scopes
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3. Reuse Spring infrastructure to create custom scopes
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