Add @Required annotation with optional validator #1558
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,29 @@ | ||
| package com.slack.api.model.annotation; | ||
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| import com.slack.api.model.predicate.FieldPredicate; | ||
| import com.slack.api.model.predicate.IsNotNullFieldPredicate; | ||
| import com.slack.api.util.json.RequiredPropertyDetectionAdapterFactory; | ||
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| import java.lang.annotation.ElementType; | ||
| import java.lang.annotation.Retention; | ||
| import java.lang.annotation.RetentionPolicy; | ||
| import java.lang.annotation.Target; | ||
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| /** | ||
| * Field-level annotation indicating whether the field is a "required" field or not on the model object. | ||
| * <p> | ||
| * The enforcement of the field's presence in instantiated instances of the model object is accomplished using the | ||
| * {@link RequiredPropertyDetectionAdapterFactory} which ensures all fields marked with {@link Required} are | ||
| * present during the object deserialization (or serialization) process. Note that the enforcement of this annotation | ||
| * is opt-in and defaults to "off". | ||
| */ | ||
| @Retention(RetentionPolicy.RUNTIME) | ||
| @Target(ElementType.FIELD) | ||
| public @interface Required { | ||
| /** | ||
| * Optional predicate to evaluate against the field annotated with {@link Required}. By default, all fields | ||
| * marked with {@link Required} are checked for null. Primitive field types are initialized by the JVM, and thus | ||
| * are never null by default. | ||
| */ | ||
| Class<? extends FieldPredicate> validator() default IsNotNullFieldPredicate.class; | ||
| } |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,11 @@ | ||
| package com.slack.api.model.predicate; | ||
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| /** | ||
| * A functional interface for defining validation predicates against {@link java.lang.reflect.Field}. Used by | ||
| * {@link com.slack.api.model.annotation.Required} during object serialization and deserialization to ensure the | ||
| * field member is "valid" per the defined predicate. | ||
| */ | ||
| @FunctionalInterface | ||
| public interface FieldPredicate { | ||
| boolean validate(Object obj); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,10 @@ | ||
| package com.slack.api.model.predicate; | ||
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| import java.util.Objects; | ||
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| public class IsNotNullFieldPredicate implements FieldPredicate { | ||
| @Override | ||
| public boolean validate(Object obj) { | ||
| return Objects.nonNull(obj); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,111 @@ | ||
| package com.slack.api.util.json; | ||
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| import com.google.gson.JsonParseException; | ||
| import com.google.gson.Gson; | ||
| import com.google.gson.TypeAdapterFactory; | ||
| import com.google.gson.TypeAdapter; | ||
| import com.google.gson.reflect.TypeToken; | ||
| import com.google.gson.stream.JsonReader; | ||
| import com.google.gson.stream.JsonWriter; | ||
| import com.slack.api.model.predicate.FieldPredicate; | ||
| import com.slack.api.model.annotation.Required; | ||
| import lombok.EqualsAndHashCode; | ||
| import lombok.RequiredArgsConstructor; | ||
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| import java.lang.reflect.Field; | ||
| import java.lang.reflect.InvocationTargetException; | ||
| import java.util.ArrayList; | ||
| import java.util.Collections; | ||
| import java.util.List; | ||
| import java.io.IOException; | ||
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| /** | ||
| * Adapter factory for processing objects annotated with {@link Required}. This annotation signals what properties | ||
| * of a model object are required, and thus should be expected to be initialized on instantiated instances. For all | ||
| * fields on the model objected annotated with {@link Required} applies the {@link FieldPredicate#test(Object)} via the | ||
| * specified {@link Required#validator()}. | ||
| * <p> | ||
| * Note that this adapter handles both deserialization (JSON --> POJO) and serialization (POJO --> JSON). | ||
| */ | ||
| public class RequiredPropertyDetectionAdapterFactory implements TypeAdapterFactory { | ||
| @Override | ||
| public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) { | ||
| TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type); | ||
| List<RequiredFieldEntry> entries = buildRequiredFieldEntries(type.getRawType()); | ||
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| if (entries.isEmpty()) { | ||
| return delegate; | ||
| } | ||
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| return new TypeAdapter<T>() { | ||
| @Override | ||
| public void write(JsonWriter out, T value) throws IOException { | ||
| if (value != null) { | ||
| ensureFieldValidity(value, entries); | ||
| } | ||
| delegate.write(out, value); | ||
| } | ||
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| @Override | ||
| public T read(JsonReader in) throws IOException { | ||
| T result = delegate.read(in); | ||
| if (result == null) { | ||
| return null; | ||
| } | ||
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| ensureFieldValidity(result, entries); | ||
| return result; | ||
| } | ||
| }; | ||
| } | ||
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| /** | ||
| * Scans the given class for fields annotated with {@link Required}, pre-resolves each field's | ||
| * accessibility and {@link FieldPredicate} instance, and returns an immutable list of entries. | ||
| * This is called once per type during Gson adapter creation. | ||
| */ | ||
| private List<RequiredFieldEntry> buildRequiredFieldEntries(Class<?> clazz) { | ||
| List<RequiredFieldEntry> entries = new ArrayList<>(); | ||
| for (Field field : clazz.getDeclaredFields()) { | ||
| Required annotation = field.getAnnotation(Required.class); | ||
| if (annotation != null) { | ||
| field.setAccessible(true); | ||
| try { | ||
| FieldPredicate predicate = annotation.validator().getDeclaredConstructor().newInstance(); | ||
| entries.add(new RequiredFieldEntry(field, predicate)); | ||
| } catch (NoSuchMethodException | InstantiationException | | ||
| IllegalAccessException | InvocationTargetException e) { | ||
| throw new JsonParseException( | ||
| "Cannot instantiate validator for field: " + field.getName(), e); | ||
| } | ||
| } | ||
| } | ||
| return Collections.unmodifiableList(entries); | ||
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fst-john marked this conversation as resolved.
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| } | ||
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| private <T> void ensureFieldValidity(T obj, List<RequiredFieldEntry> entries) { | ||
| for (RequiredFieldEntry entry : entries) { | ||
| try { | ||
| Object value = entry.field.get(obj); | ||
| if (!entry.predicate.validate(value)) { | ||
| throw new JsonParseException("Required field '" + entry.field.getName() | ||
| + "' failed validation in " + obj.getClass().getSimpleName() | ||
| + " using predicate " + entry.predicate.getClass().getSimpleName()); | ||
| } | ||
| } catch (IllegalAccessException e) { | ||
| throw new JsonParseException( | ||
| "Cannot access field: " + entry.field.getName(), e); | ||
| } | ||
| } | ||
| } | ||
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| /** | ||
| * Class holding the accessible {@link Field} handle and the cached instance of {@link FieldPredicate}. | ||
| */ | ||
| @RequiredArgsConstructor | ||
| @EqualsAndHashCode | ||
| private static class RequiredFieldEntry { | ||
| final Field field; | ||
| final FieldPredicate predicate; | ||
| } | ||
| } | ||
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