diff --git a/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/BeanInfo.java b/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/BeanInfo.java index 2aeb0a49..df54baab 100644 --- a/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/BeanInfo.java +++ b/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/BeanInfo.java @@ -10,6 +10,7 @@ package jakarta.enterprise.inject.build.compatible.spi; +import jakarta.enterprise.invoke.InvokerBuilder; import jakarta.enterprise.lang.model.AnnotationInfo; import jakarta.enterprise.lang.model.declarations.ClassInfo; import jakarta.enterprise.lang.model.declarations.FieldInfo; @@ -162,6 +163,25 @@ public interface BeanInfo { */ Collection injectionPoints(); + /** + * Returns a new {@link InvokerBuilder} for given method. The builder eventually produces + * an opaque representation of the invoker for the given method. + *

+ * The {@code method} must be declared on the bean class or inherited from a supertype + * of the bean class of this bean, otherwise an exception is thrown. + *

+ * If an invoker may not be obtained for given {@code method} as described + * in {@link jakarta.enterprise.invoke.Invoker Invoker}, an exception is thrown. + *

+ * If this method is called outside the {@code @Registration} phase, an exception is thrown. + * + * @param method method of this bean, must not be {@code null} + * @return the invoker builder, never {@code null} + * @since 4.1 + */ + // TODO we may want to introduce another entrypoint for this operation + InvokerBuilder createInvoker(MethodInfo method); + // --- /** diff --git a/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/InvokerInfo.java b/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/InvokerInfo.java new file mode 100644 index 00000000..d0038c4a --- /dev/null +++ b/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/InvokerInfo.java @@ -0,0 +1,25 @@ +/* + * Copyright (c) 2022 Red Hat and others + * + * This program and the accompanying materials are made available under the + * Apache Software License 2.0 which is available at: + * https://www.apache.org/licenses/LICENSE-2.0. + * + * SPDX-License-Identifier: Apache-2.0 + */ + +package jakarta.enterprise.inject.build.compatible.spi; + +import jakarta.enterprise.invoke.Invoker; +import jakarta.enterprise.lang.model.declarations.MethodInfo; + +/** + * Opaque token that stands in for an invoker registered using {@link BeanInfo#createInvoker(MethodInfo)}. + * It can only be used to materialize an {@link Invoker} in a synthetic component; see + * {@link SyntheticBeanBuilder#withParam(String, InvokerInfo) SyntheticBeanBuilder.withParam()} or + * {@link SyntheticObserverBuilder#withParam(String, InvokerInfo) SyntheticObserverBuilder.withParam()}. + * + * @since 4.1 + */ +public interface InvokerInfo { +} diff --git a/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/Parameters.java b/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/Parameters.java index 54ad368d..96b28dc7 100644 --- a/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/Parameters.java +++ b/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/Parameters.java @@ -10,6 +10,8 @@ package jakarta.enterprise.inject.build.compatible.spi; +import jakarta.enterprise.invoke.Invoker; + /** * A {@code String}-keyed parameter map. The parameter mappings are defined * by a synthetic component builder. The CDI container passes the parameter map @@ -40,13 +42,16 @@ *

* Annotation-typed parameters are available as instances of the annotation type, * even if an instance of {@code AnnotationInfo} was passed to the builder. + *

+ * Invoker-typed parameters are available as instances of {@link Invoker}, even though + * an instance of {@code InvokerInfo} was passed to the builder. */ public interface Parameters { /** * Returns the value of a parameter with given {@code key}. The value is expected to be of given {@code type}. * - * @param key the parameter key; must not be {@code null} - * @param type the parameter type; must not be {@code null} + * @param key the parameter key, must not be {@code null} + * @param type the parameter type, must not be {@code null} * @param the parameter type * @return the parameter value, or {@code null} if parameter with given {@code key} does not exist * @throws ClassCastException if the parameter exists, but is of a different type @@ -57,8 +62,8 @@ public interface Parameters { * Returns the value of a parameter with given {@code key}. The value is expected to be of given {@code type}. * If the parameter does not exist, returns {@code defaultValue}. * - * @param key the parameter key; must not be {@code null} - * @param type the parameter type; must not be {@code null} + * @param key the parameter key, must not be {@code null} + * @param type the parameter type, must not be {@code null} * @param defaultValue the value to return if parameter with given {@code key} does not exist * @param the parameter type * @return the parameter value, or {@code defaultValue} if parameter with given {@code key} does not exist diff --git a/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/SyntheticBeanBuilder.java b/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/SyntheticBeanBuilder.java index 2f2b8f1e..8afb2c94 100644 --- a/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/SyntheticBeanBuilder.java +++ b/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/SyntheticBeanBuilder.java @@ -405,6 +405,36 @@ public interface SyntheticBeanBuilder { */ SyntheticBeanBuilder withParam(String key, Annotation[] value); + /** + * Adds an invoker-valued parameter to the parameter map. The parameter map is passed + * to the {@linkplain SyntheticBeanCreator creation} and {@linkplain SyntheticBeanDisposer destruction} + * functions when a bean instance is created/destroyed. + *

+ * When looked up from the parameter map in the creation/destruction function, the value will be + * an instance of {@link jakarta.enterprise.invoke.Invoker Invoker}, not an {@code InvokerInfo}. + * + * @param key the parameter key, must not be {@code null} + * @param value the parameter value + * @return this {@code SyntheticBeanBuilder} + * @since 4.1 + */ + SyntheticBeanBuilder withParam(String key, InvokerInfo value); + + /** + * Adds an invoker array-valued parameter to the parameter map. The parameter map is passed + * to the {@linkplain SyntheticBeanCreator creation} and {@linkplain SyntheticBeanDisposer destruction} + * functions when a bean instance is created/destroyed. + *

+ * When looked up from the parameter map in the creation/destruction function, the values will be + * instances of {@link jakarta.enterprise.invoke.Invoker Invoker}, not {@code InvokerInfo}. + * + * @param key the parameter key, must not be {@code null} + * @param value the parameter value + * @return this {@code SyntheticBeanBuilder} + * @since 4.1 + */ + SyntheticBeanBuilder withParam(String key, InvokerInfo[] value); + /** * Sets the class of the synthetic bean {@linkplain SyntheticBeanCreator creation} function. * CDI container will create an instance of the creation function every time when it needs diff --git a/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/SyntheticObserverBuilder.java b/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/SyntheticObserverBuilder.java index 25fffcb7..4e2b102c 100644 --- a/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/SyntheticObserverBuilder.java +++ b/api/src/main/java/jakarta/enterprise/inject/build/compatible/spi/SyntheticObserverBuilder.java @@ -334,6 +334,34 @@ public interface SyntheticObserverBuilder { */ SyntheticObserverBuilder withParam(String key, Annotation[] value); + /** + * Adds an invoker-valued parameter to the parameter map. The parameter map is passed + * to the {@linkplain SyntheticObserver event notification} function when the event is fired. + *

+ * When looked up from the parameter map in the event notification function, the value will be + * an instance of {@link jakarta.enterprise.invoke.Invoker Invoker}, not an {@code InvokerInfo}. + * + * @param key the parameter key, must not be {@code null} + * @param value the parameter value + * @return this {@code SyntheticBeanBuilder} + * @since 4.1 + */ + SyntheticObserverBuilder withParam(String key, InvokerInfo value); + + /** + * Adds an invoker array-valued parameter to the parameter map. The parameter map is passed + * to the {@linkplain SyntheticObserver event notification} function when the event is fired. + *

+ * When looked up from the parameter map in the event notification function, the values will be + * instances of {@link jakarta.enterprise.invoke.Invoker Invoker}, not {@code InvokerInfo}. + * + * @param key the parameter key, must not be {@code null} + * @param value the parameter value + * @return this {@code SyntheticBeanBuilder} + * @since 4.1 + */ + SyntheticObserverBuilder withParam(String key, InvokerInfo[] value); + /** * Sets the class of the synthetic observer {@linkplain SyntheticObserver event notification} function. * CDI container will create an instance of the event notification function every time when it needs diff --git a/api/src/main/java/jakarta/enterprise/inject/spi/ProcessManagedBean.java b/api/src/main/java/jakarta/enterprise/inject/spi/ProcessManagedBean.java index f2cd0b21..9b10bd86 100644 --- a/api/src/main/java/jakarta/enterprise/inject/spi/ProcessManagedBean.java +++ b/api/src/main/java/jakarta/enterprise/inject/spi/ProcessManagedBean.java @@ -15,6 +15,9 @@ */ package jakarta.enterprise.inject.spi; +import jakarta.enterprise.invoke.Invoker; +import jakarta.enterprise.invoke.InvokerBuilder; + /** *

* The container fires an event of this type for each enabled managed bean, before registering the @@ -38,4 +41,17 @@ public interface ProcessManagedBean extends ProcessBean { * @throws IllegalStateException if called outside of the observer method invocation */ public AnnotatedType getAnnotatedBeanClass(); + + /** + * Returns a new {@link InvokerBuilder} for given method. The builder eventually produces an invoker + * for the given method. + *

+ * The {@code method} must be declared on the bean class or inherited from a supertype + * of the bean class of the bean being registered, otherwise an exception is thrown. + * + * @param method method of the bean being registered, must not be {@code null} + * @return the invoker builder, never {@code null} + * @since 4.1 + */ + public InvokerBuilder> createInvoker(AnnotatedMethod method); } diff --git a/api/src/main/java/jakarta/enterprise/invoke/Invoker.java b/api/src/main/java/jakarta/enterprise/invoke/Invoker.java new file mode 100644 index 00000000..ede8faa8 --- /dev/null +++ b/api/src/main/java/jakarta/enterprise/invoke/Invoker.java @@ -0,0 +1,132 @@ +/* + * Copyright (c) 2022 Red Hat and others + * + * This program and the accompanying materials are made available under the + * Apache Software License 2.0 which is available at: + * https://www.apache.org/licenses/LICENSE-2.0. + * + * SPDX-License-Identifier: Apache-2.0 + */ + +package jakarta.enterprise.invoke; + +/** + * Allows indirectly invoking a method that belongs to a managed bean (the target method). + * To invoke the method, the caller must provide all the arguments that the target method accepts, + * as well as the instance on which the target method is to be invoked, if it is not {@code static}. + *

+ * Whenever a direct invocation of a method is a business method invocation, an indirect invocation + * of that method through an invoker is also a business method invocation. + *

+ * Invoker implementations must be thread-safe. It is possible to use a single invoker instance + * to perform multiple independent invocations of the target method, possibly on different instances + * and with different arguments. + * + *

Obtaining an invoker

+ * + * The CDI container allows {@linkplain InvokerBuilder building} an invoker for non-private + * methods declared on a managed bean class or inherited from a supertype. Attempting to build + * an invoker for a private method or a constructor of a managed bean class leads to a deployment + * problem. Attempting to build an invoker for a method of a class that is not a managed bean class + * or that is an interceptor or decorator class leads to a deployment problem. + *

+ * Multiple managed beans may inherit a method from a common supertype. In that case, each bean + * conceptually has its own method and an invoker obtained for one bean may not be used to invoke + * the method on the other bean. + *

+ * Using the {@link InvokerBuilder} is the only way to obtain an invoker. An {@code InvokerBuilder} + * can only be obtained in CDI portable extensions and build compatible extensions. + * + *

Example

+ * + * To illustrate how invokers work, let's take a look at an example. Say that the following bean + * exists and has a method that you want to invoke indirectly: + * + * 
+ * @Dependent
+ * class MyService {
+ *     String hello(String name) {
+ *         return "Hello " + name + "!";
+ *     }
+ * }
+ *
+ * + * When you obtain an {@code InvokerBuilder} for the {@code hello()} method, you can + * immediately build a direct invoker. In a portable extension, this results in an invoker: + * + * 
+ * InvokerBuilder<Invoker<MyService, String>> builder = ...;
+ * Invoker<MyService, String> invoker = builder.build();
+ *
+ * + * In a build compatible extension, this results in an opaque token that later + * materializes as an invoker: + * + * 
+ * InvokerBuilder<InvokerInfo> builder = ...;
+ * InvokerInfo invoker = builder.build();
+ *
+ * + * To call the {@code hello()} method through this invoker, call + * {@code invoker.invoke(myService, new Object[] {"world"})}. + * The return value is {@code "Hello world!"}. + *

+ * An implementation of the direct invoker above is equivalent to the following class: + * + * 

+ * class TheInvoker implements Invoker<MyService, String> {
+ *     String invoke(MyService instance, Object[] arguments) {
+ *         return instance.hello((String) arguments[0]);
+ *     }
+ * }
+ *
+ * + * @param type of the target instance + * @param return type of the method + * @since 4.1 + * @see #invoke(Object, Object[]) + */ +public interface Invoker { + /** + * Invokes the target method of this invoker on given {@code instance}, passing given + * {@code arguments}. If the target method is {@code static}, the {@code instance} is ignored; + * by convention, it should be {@code null}. If the target method returns normally, this + * method returns its return value, unless the target method is declared {@code void}, + * in which case this method returns {@code null}. If the target method throws an exception, + * this method rethrows it directly. + *

+ * If some parameter of the target method declares a primitive type, the corresponding element of + * the {@code arguments} array must be of the corresponding wrapper type. No type conversions are + * performed, so if the parameter is declared {@code int}, the argument must be an {@code Integer} + * and may not be {@code Short} or {@code Long}. If the argument is {@code null}, the default value + * of the primitive type is used. Note that this does not apply to arrays of primitive types; + * if a parameter is declared {@code int[]}, the argument must be {@code int[]} and may not be + * {@code Integer[]}. + *

+ * If the target method is not {@code static} and {@code instance} is {@code null}, + * a {@link NullPointerException} is thrown. If the target method is not {@code static} and + * the {@code instance} is not assignable to the class of the bean to which the method belongs, + * a {@link ClassCastException} is thrown. + *

+ * If the target method declares no parameter, {@code arguments} are ignored. If the target method + * declares any parameter and {@code arguments} is {@code null}, {@link NullPointerException} is + * thrown. If the {@code arguments} array has fewer elements than the number of parameters of + * the target method, {@link ArrayIndexOutOfBoundsException} is thrown. If the {@code arguments} + * array has more elements than the number of parameters of the target method, the excess elements + * are ignored. If some of the {@code arguments} is not assignable to the declared type of + * the corresponding parameter of the target method, {@link ClassCastException} is thrown. + * + * TODO the previous 2 paragraphs refer to "assignability", which needs to be defined somewhere! + * + * TODO when the `InvokerBuilder` applies transformations, some of the requirements above + * are no longer strictly necessary, should reflect that in this text somehow (it is already + * mentioned in `InvokerBuilder`, but that likely isn't enough) + * + * @param instance the instance on which the target method is to be invoked, may only be {@code null} + * if the method is {@code static} + * @param arguments arguments to be supplied to the target method, may only be {@code null} + * if the method declares no parameter + * @return return value of the target method, or {@code null} if the method is declared {@code void} + */ + R invoke(T instance, Object[] arguments); // TODO throws Exception ? +} diff --git a/api/src/main/java/jakarta/enterprise/invoke/InvokerBuilder.java b/api/src/main/java/jakarta/enterprise/invoke/InvokerBuilder.java new file mode 100644 index 00000000..97342ef7 --- /dev/null +++ b/api/src/main/java/jakarta/enterprise/invoke/InvokerBuilder.java @@ -0,0 +1,369 @@ +/* + * Copyright (c) 2022 Red Hat and others + * + * This program and the accompanying materials are made available under the + * Apache Software License 2.0 which is available at: + * https://www.apache.org/licenses/LICENSE-2.0. + * + * SPDX-License-Identifier: Apache-2.0 + */ + +package jakarta.enterprise.invoke; + +/** + * Builder of {@link Invoker}s that allows configuring input lookups, input and output + * transformations, and invoker wrapping. The method for which the invoker is built is + * called the target method. If a lookup is configured, the corresponding input + * of the invoker is ignored and an instance is looked up from the CDI container before + * the target method is invoked. If a transformation is configured, the corresponding input + * or output of the invoker is modified in certain way before or after the target method + * is invoked. If a wrapper is configured, the invoker is passed to custom code for getting + * invoked. As a result, the built {@code Invoker} instance may have more complex behavior + * than just directly calling the target method. + *

+ * Transformations and wrapping are expressed by ordinary methods that must have + * a pre-defined signature, as described below. Such methods are called + * transformers and wrappers. + *

+ * Invokers may only be built during deployment. It is not possible to build new invokers + * at application runtime. + * + *

Example

+ * + * Before describing in detail how lookups, transformers and wrappers work, let's take + * a look at an example. Say we have the following bean with a method: + * + * 
+ * class MyService {
+ *     String hello(String name) {
+ *         return "Hello " + name + "!";
+ *     }
+ * }
+ *
+ * + * And we want to build an invoker that looks up {@code MyService} from the CDI container, + * always passes the argument to {@code hello()} as all upper-case, and repeats the return + * value twice. To transform the argument, we can use the zero-parameter method + * {@code String.toUpperCase()}, and to transform the return value, we write a transformer + * as a simple {@code static} method: + * + * 
+ * class Transformations {
+ *     static String repeatTwice(String str) {
+ *         return str + " " + str;
+ *     }
+ * }
+ *
+ * + * Then, assuming we have obtained the {@code InvokerBuilder} for {@code MyService.hello()}, + * we can set up the lookup and transformations and build an invoker like so: + * + * 
+ * builder.setInstanceLookup()
+ *        .setArgumentTransformer(0, String.class, "toUpperCase")
+ *        .setReturnValueTransformer(Transformations.class, "repeatTwice")
+ *        .build();
+ *
+ * + * The resulting invoker will be equivalent to the following class: + * 
+ * class TheInvoker implements Invoker<MyService, String> {
+ *     String invoke(MyService ignored, Object[] arguments) {
+ *         MyService instance = CDI.current().select(MyService.class).get();
+ *         String argument = (String) arguments[0];
+ *         String transformedArgument = argument.toUpperCase();
+ *         String result = instance.hello(transformedArgument);
+ *         String transformedResult = Transformations.repeatTwice(result);
+ *         return transformedResult;
+ *     }
+ * }
+ *
+ * + * The caller of this invoker may pass {@code null} as the target instance, because + * the invoker will lookup the target instance on its own. Therefore, calling + * {@code invoker.invoke(null, new Object[] {"world"})} will return + * {@code "Hello WORLD! Hello WORLD!"}. + * + *

General requirements

+ * + * To refer to a transformer or a wrapper, all methods in this builder accept: + * 1. the {@code Class} that that declares the method, and 2. the {@code String} name + * of the method. + *

+ * Transformers may be {@code static}, in which case they must be declared directly + * on the given class, or they may be instance methods, in which case they may be declared + * on the given class or inherited from any of its supertypes. + *

+ * It is possible to register only one transformer of each kind, or for each argument + * position in case of argument transformers. Attempting to register a second transformer + * of the same kind, or for the same argument position, leads to an exception. + *

+ * Wrappers must be {@code static} and must be declared directly on the given class. + * It is possible to register only one wrapper. Attempting to register a second wrapper + * leads to an exception. + *

+ * It is a deployment problem if no method with given name and valid signature is found, + * or if multiple methods with given name and different valid signatures are found. It is + * a deployment problem if a registered transformer or wrapper is not {@code public}. + *

+ * Transformers and wrappers may declare the {@code throws} clause. The declared exception + * types are ignored when searching for the method. + *

+ * For the purpose of the specification of transformers and wrappers below, the term + * any-type is recursively defined as: the {@code java.lang.Object} class type, + * or a type variable that has no bound, or a type variable whose first bound is + * any-type. + * + *

Input lookups

+ * + * For the target instance and for each argument, it is possible to specify that the value + * passed to {@code Invoker.invoke()} should be ignored and a value should be looked up + * from the CDI container instead. + *

+ * For the target instance, a CDI lookup is performed with the required type equal to the bean + * class of the bean to which the target method belongs, and required qualifiers equal to the set + * of all qualifier annotations present on the bean class of the bean to which the target method + * belongs. When the target method is {@code static}, the target instance lookup is skipped. + *

+ * For an argument, a CDI lookup is performed with the required type equal to the type of + * the corresponding parameter of the target method, and required qualifiers equal to the set + * of all qualifier annotations present on the corresponding parameter of the target method. + *

+ * Implementations are required to resolve all lookups during deployment. It is a deployment + * problem if the lookup ends up unresolved or ambiguous. + *

+ * If the looked up bean is {@code @Dependent}, it is guaranteed that the instance will be + * destroyed after the target method is invoked but before the the invoker returns. The order + * in which the looked up {@code @Dependent} beans are destroyed is not specified. + *

+ * The order in which input lookups are performed in not specified and must not be relied upon. + * + *

Input transformations

+ * + * The target method has 2 kinds of inputs: the target instance (unless the target method is + * {@code static}, in which case the target instance is ignored and should be {@code null} + * by convention) and arguments. These inputs correspond to the parameters of + * {@link Invoker#invoke(Object, Object[]) Invoker.invoke()}. + *

+ * Each input can be transformed by a transformer that has one of the following signatures, + * where {@code X} and {@code Y} are types: + * + *

    + *
  • {@code static X transform(Y value)}
    • + *
  • {@code static X transform(Y value, Consumer cleanup)}
    • + *
  • {@code X transform()} – in this case, {@code Y} is the type of the class that + * declares the transformer
    • + *
+ * + * An input transformer must produce a type that can be consumed by the target method. + * Specifically: when {@code X} is any-type, it is not type checked during deployment. + * Otherwise, it is a deployment problem if {@code X} is not assignable to the corresponding type + * in the declaration of the target method (that is the bean class in case of target instance + * transformers, or the corresponding parameter type in case of argument transformers). {@code Y} + * is not type checked during deployment, so that input transformers may consume arbitrary types. + * TODO this paragraph refers to "assignability", which needs to be defined somewhere! + *

+ * When a transformer is registered for given input, it is called before the target method is + * invoked, and the outcome of the transformer is used in the invocation instead of the original + * value passed to the invoker by its caller. + *

+ * If the transformer declares the {@code Consumer} parameter, and the execution + * of the transformer calls {@code Consumer.accept()} with some {@code Runnable}, it is + * guaranteed that the {@code Runnable} will be called after the target method is invoked but + * before the invoker returns. These {@code Runnable}s are called cleanup tasks. + * The order of cleanup task execution is not specified. Passing a {@code null} cleanup task + * to the {@code Consumer} is permitted, but has no effect. + *

+ * If an input transformation is configured for an input for which a lookup is also configured, + * the lookup is performed first and the transformation is applied to the looked up value. + * If the looked up bean for some input is {@code @Dependent}, it is guaranteed that all + * cleanup tasks registered by a transformer for that input are called before that looked up + * {@code @Dependent} bean is destroyed. + *

+ * The order in which input transformations are performed in not specified and must not + * be relied upon. + * + *

Output transformations

+ * + * The target method has 2 kinds of outputs: the return value and the thrown exception. These + * outputs correspond to the return value of {@link Invoker#invoke(Object, Object[]) Invoker.invoke()} + * or its thrown exception, respectively. + *

+ * Each output can be transformed by a transformer that has one of the following signatures, + * where {@code X} and {@code Y} are types: + * + *

    + *
  • {@code static X transform(Y value)}
    • + *
  • {@code X transform()} – in this case, {@code Y} is the type of the class that + * declares the transformer
    • + *
+ * + * An output transformer must consume a type that can be produced by the target method. + * Specifically: when {@code Y} is any-type, it is not type checked during deployment. + * Otherwise, it is a deployment problem if {@code Y} is not assignable from the return type of + * the target method in case of return value transformers, or from {@code java.lang.Throwable} + * in case of exception transformers. {@code X} is not type checked during deployment, so that + * output transformers may produce arbitrary types. + * TODO this paragraph refers to "assignability", which needs to be defined somewhere! + *

+ * When a transformer is registered for given output, it is called after the target method + * is invoked, and the outcome of the transformer is passed back to the caller of the invoker + * instead of the original output produced by the target method. + *

+ * If the target method returns normally, any registered exception transformer is ignored; only + * the return value transformer is called. The return value transformer may throw, in which case + * the invoker will rethrow the exception. If the invoker is supposed to return normally, + * the return value transformer must return normally. + *

+ * Similarly, if the target method throws, any registered return value transformer is ignored; + * only the exception transformer is called. The exception transformer may return normally, + * in which case the invoker will return the return value of the exception transformer. If + * the invoker is supposed to throw an exception, the exception transformer must throw. + * TODO this requires that implementations catch java.lang.Throwable, which is perhaps a bit too much? + * maybe stick with java.lang.Exception? + * + *

Invoker wrapping

+ * + * An invoker, possibly utilizing input lookups and input/output transformations, may be wrapped + * by a custom piece of code for maximum flexibility. A wrapper must have the following signature, + * where {@code X}, {@code Y} and {@code Z} are types: + * + *
    + *
  • {@code static Z wrap(X instance, Object[] arguments, Invoker invoker)}
    • + *
+ * + * A wrapper must operate on a matching instance type. Specifically: when {@code X} is + * any-type, it is not type checked during deployment. Otherwise, it is a deployment + * problem if {@code X} is not assignable from the class type of the bean class to which + * the target method belongs. {@code Y} and {@code Z} are not type checked during deployment. + *

+ * When a wrapper is registered, 2 invokers for the same method are created. The inner + * invoker applies all lookups and transformations, as described in previous sections, and + * invokes the target method. The outer invoker calls the wrapper with the passed + * instance and arguments and an instance of the inner invoker. The outer invoker is returned + * by this invoker builder. + *

+ * In other words, the outer invoker is equivalent to the following class: + * + * 

+ * class InvokerWrapper implements Invoker<X, Z> {
+ *     Z invoke(X instance, Object[] arguments) {
+ *         // obtain the invoker as if no wrapper existed
+ *         Invoker<X, Y> invoker = obtainInvoker();
+ *         return SomeClass.wrap(instance, arguments, invoker);
+ *     }
+ * }
+ *
+ * + * If the wrapper returns normally, the outer invoker returns its return value, unless the wrapper + * is declared {@code void}, in which case the outer invoker returns {@code null}. If the wrapper + * throws an exception, the outer invoker rethrows it directly. + *

+ * The wrapper is supposed to call the invoker it is passed, but does not necessarily have to. + * The wrapper may call the invoker multiple times. The wrapper must not use the invoker + * in any other way; specifically, it is forbidden to store the invoker instance anywhere + * or pass it to other methods that do not follow these rules. Doing so leads to non-portable + * behavior. + * + *

Type checking

+ * + * An invoker created by this builder has relaxed type checking rules, when compared to + * the description in {@link Invoker#invoke(Object, Object[]) Invoker.invoke()}, depending + * on configured lookups, transformers and wrapper. Some types are checked during + * deployment, as described in previous sections. Other types are checked during invocation, + * at the very least due to the type checks performed implicitly by the JVM. The lookups, + * transformers and the wrapper must arrange the inputs and outputs so that when the method + * is eventually invoked, the rules described in + * {@link Invoker#invoke(Object, Object[]) Invoker.invoke()} all hold. + *

+ * TODO specify what happens when a transformer/wrapper declares a parameter of a primitive type + * but the actual value passed to the invoker is `null` (the transformer should get a zero value?) + * TODO specify what happens when a transformer/wrapper declares a parameter of some type + * but the actual value passed to the invoker is not assignable to it (CCE?) + * + * @param type of outcome of this builder; always represents an {@code Invoker}, + * but does not necessarily have to be an {@code Invoker} instance directly + * @since 4.1 + */ +// TODO more kinds of transformations could be defined, expecially for argument handling +// TODO it would be possible to specify a sequence of transformations for each input/output, instead of just one +public interface InvokerBuilder { + /** + * Enables lookup of the target instance. + * + * @return this builder + */ + InvokerBuilder setInstanceLookup(); + + /** + * Enables lookup of the argument on given {@code position}. + * + * @param position zero-based argument position for which lookup is enabled + * @return this builder + * @throws IllegalArgumentException if {@code position} is greather than or equal to + * the number of parameters declared by the target method + */ + InvokerBuilder setArgumentLookup(int position); + + /** + * Configures an input transformer for the target instance. + * + * @param clazz class that declares the transformer + * @param methodName transformer method name + * @return this builder + * @throws IllegalStateException if this method is called more than once + */ + InvokerBuilder setInstanceTransformer(Class clazz, String methodName); + + /** + * Configures an input transformer for the argument on given {@code position}. + * + * @param position zero-based argument position for which the input transformer is configured + * @param clazz class that declares the transformer + * @param methodName transformer method name + * @return this builder + * @throws IllegalArgumentException if {@code position} is greather than or equal to + * the number of parameters declared by the target method + * @throws IllegalStateException if this method is called more than once with the same {@code position} + */ + InvokerBuilder setArgumentTransformer(int position, Class clazz, String methodName); + + /** + * Configures an output transformer for the return value. + * + * @param clazz class that declares the transformer + * @param methodName transformer method name + * @return this builder + * @throws IllegalStateException if this method is called more than once + */ + InvokerBuilder setReturnValueTransformer(Class clazz, String methodName); + + /** + * Configures an output transformer for the thrown exception. + * + * @param clazz class that declares the transformer + * @param methodName transformer method name + * @return this builder + * @throws IllegalStateException if this method is called more than once + */ + InvokerBuilder setExceptionTransformer(Class clazz, String methodName); + + /** + * Configures an invoker wrapper. + * + * @param clazz class that declares the invoker wrapper + * @param methodName invoker wrapper method name + * @return this builder + * @throws IllegalStateException if this method is called more than once + */ + InvokerBuilder setInvocationWrapper(Class clazz, String methodName); + + /** + * Returns the built {@link Invoker} or some represention of it. Implementations are allowed + * but not required to reuse already built invokers for the same target method with the same + * configuration. + * + * @return the built invoker + */ + T build(); +} diff --git a/api/src/main/java/module-info.java b/api/src/main/java/module-info.java index 1aa23218..4239d4d3 100644 --- a/api/src/main/java/module-info.java +++ b/api/src/main/java/module-info.java @@ -10,6 +10,7 @@ exports jakarta.enterprise.inject.se; exports jakarta.enterprise.inject.spi; exports jakarta.enterprise.inject.spi.configurator; + exports jakarta.enterprise.invoke; exports jakarta.enterprise.util; requires transitive jakarta.annotation;