我在 Java SE 应用程序(没有任何应用程序服务器)中有一个 Service
,它创建 Algorithm
实例并运行它们。
- 每个
Algorithm
实例都需要一个新的(单独的)ActionExecutor
和一个新的(单独的)AlgorithmState
。 ActionExecutor
还需要一个AlgorithmState
实例,该实例必须与Algorithm
获取的相同。
如何使用 CDI 实现这一目标?我已经在 Algorithm
的两个参数上尝试了构造函数注入(inject)和 @New
,但我想这不是我想要的。
服务
类:
import java.util.ArrayList;
import java.util.List;
import javax.enterprise.inject.Instance;
import javax.inject.Inject;
public class Service {
@Inject
private Instance<Algorithm> algorithmInstance;
public void run() {
final List<Algorithm> algorithms = new ArrayList<>();
for (int i = 0; i < 3; i++) {
final Algorithm algorithm = algorithmInstance.get();
algorithms.add(algorithm);
}
for (final Algorithm algorithm: algorithms) {
algorithm.doSomething();
}
}
}
算法
类:
import java.util.concurrent.atomic.AtomicInteger;
import javax.enterprise.inject.New;
import javax.inject.Inject;
public class Algorithm {
private static final AtomicInteger counter = new AtomicInteger(100);
private final ActionExecutor actionExecutor;
private final AlgorithmState algorithmState;
private final int id;
@Inject
public Algorithm(@New final ActionExecutor actionExecutor, @New final AlgorithmState algorithmState) {
this.actionExecutor = actionExecutor;
this.algorithmState = algorithmState;
id = counter.incrementAndGet();
System.out.println("algorithm ctor#" + id);
}
public void doSomething() {
System.out.printf("do something, algorithm id: #%d: executor id%sd, stateId: %d, executor->stateId: %d%n", id,
actionExecutor.getId(), algorithmState.getId(), actionExecutor.getAlgorithmStateId());
}
}
ActionExecutor
类:
import java.util.concurrent.atomic.AtomicInteger;
import javax.inject.Inject;
public class ActionExecutor {
private static AtomicInteger counter = new AtomicInteger(200);
private final AlgorithmState algorithmState;
private final int id;
@Inject
public ActionExecutor(final AlgorithmState algorithmState) {
this.algorithmState = algorithmState;
id = counter.incrementAndGet();
}
public int getId() {
return id;
}
public int getAlgorithmStateId() {
return algorithmState.getId();
}
}
AlgorithmState
类:
import java.util.concurrent.atomic.AtomicInteger;
import javax.annotation.PostConstruct;
import javax.inject.Inject;
public class AlgorithmState {
private static final AtomicInteger counter = new AtomicInteger(300);
private final int id;
@Inject
public AlgorithmState() {
id = counter.incrementAndGet();
}
@PostConstruct
public void start() {
System.out.println("state start#" + id);
}
public int getId() {
return id;
}
}
还有一个用于测试的 ServiceMain
类:
import java.util.List;
import javax.enterprise.event.Observes;
import javax.inject.Inject;
import org.jboss.weld.environment.se.bindings.Parameters;
import org.jboss.weld.environment.se.events.ContainerInitialized;
public class ServiceMain {
@Inject
private Service service;
public void printHello(
@Observes final ContainerInitialized event,
@Parameters final List<String> parameters) {
System.out.println("ServiceMain:" + service);
service.run();
}
public static void main(final String[] args) {
org.jboss.weld.environment.se.StartMain.main(args);
}
}
目前它打印以下内容:
do something, algorithm id: #101: executor id201d, stateId: 302, executor->stateId: 301
do something, algorithm id: #102: executor id202d, stateId: 304, executor->stateId: 303
do something, algorithm id: #103: executor id203d, stateId: 306, executor->stateId: 305
我需要的是 stateId
和 executor->stateId
相同:
do something, algorithm id: #101: executor id201d, stateId: 301, executor->stateId: 301
do something, algorithm id: #102: executor id202d, stateId: 302, executor->stateId: 302
do something, algorithm id: #103: executor id203d, stateId: 303, executor->stateId: 303
编辑:
目前我正在从AlgorithmExecutor
获取AlgorithmState
,但它弄乱了模型,我想避免这种情况。
最佳答案
首先,@New
限定符被替换为 @Dependant
作用域,这是默认作用域。我想它在 CDI 1.1 中由于它引起的困惑而被更改。另外,@New
是一个限定符,而不是一个范围,并且来自一个可用于多种用途的单独标准(我不认为 @New
真的被使用了按任何标准)。
看起来您想在 AlgorithmState
中使用 @Produces
而不是 @Inject
。查看Weld documentation on the subject了解更多详情。您可能想要创建一个特定的 scoped type像这样:
@ScopeType
@Retention(RUNTIME)
@Target({TYPE, METHOD, CONSTRUCTOR})
public @interface AlgorithmScoped {}
然后您可以修改AlgorithmState
构造函数:
@Produces @AlgorithmScoped
public AlgorithmState() {
// ...
}
将该范围添加到 AlgorithmExecutor
,然后也添加到 Algorithm
。我认为您不应该尝试将 AlgorithmState
注入(inject) Algorithm
;从 AlgorithmExecutor
实例中获取它!事实上,如果您这样做,简而言之应该可以解决整个问题。
关于java - 使用 CDI 在运行时创建和连接相关实例,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22376673/