Repository: incubator-beam Updated Branches: refs/heads/master f6ad58d60 -> 7e0cfe5b9
Added a where method on TypeDescriptor to allow substituting a type parameter with a TypeDescriptor. In the process introduced a TypeParameter class which represents the parameter type. This is useful when having a type such as Set<T> to be able to specify what T is as part of the TypeDescriptor information. Project: http://git-wip-us.apache.org/repos/asf/incubator-beam/repo Commit: http://git-wip-us.apache.org/repos/asf/incubator-beam/commit/699075e2 Tree: http://git-wip-us.apache.org/repos/asf/incubator-beam/tree/699075e2 Diff: http://git-wip-us.apache.org/repos/asf/incubator-beam/diff/699075e2 Branch: refs/heads/master Commit: 699075e250973447a9cdce1eb9c52d3406788212 Parents: f6ad58d Author: Jeremie Lenfant-Engelmann <jeremi...@google.com> Authored: Thu Oct 20 19:29:39 2016 -0700 Committer: Kenneth Knowles <k...@google.com> Committed: Tue Nov 1 15:14:24 2016 -0700 ---------------------------------------------------------------------- .../apache/beam/sdk/values/TypeDescriptor.java | 35 +++++++++++---- .../apache/beam/sdk/values/TypeDescriptors.java | 1 - .../apache/beam/sdk/values/TypeParameter.java | 45 ++++++++++++++++++++ .../beam/sdk/values/TypeDescriptorTest.java | 12 ++++++ 4 files changed, 83 insertions(+), 10 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/incubator-beam/blob/699075e2/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeDescriptor.java ---------------------------------------------------------------------- diff --git a/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeDescriptor.java b/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeDescriptor.java index 724b8b6..6eabf42 100644 --- a/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeDescriptor.java +++ b/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeDescriptor.java @@ -20,7 +20,7 @@ package org.apache.beam.sdk.values; import com.google.common.collect.Lists; import com.google.common.reflect.Invokable; import com.google.common.reflect.Parameter; -import com.google.common.reflect.TypeParameter; +import com.google.common.reflect.TypeResolver; import com.google.common.reflect.TypeToken; import java.io.Serializable; import java.lang.reflect.Field; @@ -171,14 +171,6 @@ public abstract class TypeDescriptor<T> implements Serializable { } /** - * Creates a new {@link SimpleTypeDescriptor} using the {@link #token}. - * Package visible so this isn't abused. - */ - <X> TypeDescriptor<T> where(TypeParameter<X> typeParam, TypeDescriptor<X> typeDescriptor) { - return new SimpleTypeDescriptor<>(token.where(typeParam, typeDescriptor.token)); - } - - /** * Returns the {@link Type} represented by this {@link TypeDescriptor}. */ public Type getType() { @@ -322,6 +314,31 @@ public abstract class TypeDescriptor<T> implements Serializable { return classes; } + /** + * Returns a new {@code TypeDescriptor} where type variables represented by + * {@code typeParameter} are substituted by {@code typeDescriptor}. For example, it can be used to + * construct {@code Map<K, V>} for any {@code K} and {@code V} type: <pre> {@code + * static <K, V> TypeDescriptor<Map<K, V>> mapOf( + * TypeDescriptor<K> keyType, TypeDescriptor<V> valueType) { + * return new TypeDescriptor<Map<K, V>>() {} + * .where(new TypeParameter<K>() {}, keyType) + * .where(new TypeParameter<V>() {}, valueType); + * }}</pre> + * + * @param <X> The parameter type + * @param typeParameter the parameter type variable + * @param typeDescriptor the actual type to substitute + */ + @SuppressWarnings("unchecked") + public <X> TypeDescriptor<T> where(TypeParameter<X> typeParameter, + TypeDescriptor<X> typeDescriptor) { + TypeResolver resolver = + new TypeResolver() + .where( + typeParameter.typeVariable, typeDescriptor.getType()); + return (TypeDescriptor<T>) TypeDescriptor.of(resolver.resolveType(token.getType())); + } + @Override public String toString() { return token.toString(); http://git-wip-us.apache.org/repos/asf/incubator-beam/blob/699075e2/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeDescriptors.java ---------------------------------------------------------------------- diff --git a/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeDescriptors.java b/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeDescriptors.java index 7a78131..b6b1a1a 100644 --- a/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeDescriptors.java +++ b/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeDescriptors.java @@ -17,7 +17,6 @@ */ package org.apache.beam.sdk.values; -import com.google.common.reflect.TypeParameter; import java.math.BigDecimal; import java.math.BigInteger; import java.util.List; http://git-wip-us.apache.org/repos/asf/incubator-beam/blob/699075e2/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeParameter.java ---------------------------------------------------------------------- diff --git a/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeParameter.java b/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeParameter.java new file mode 100644 index 0000000..a9a658e --- /dev/null +++ b/sdks/java/core/src/main/java/org/apache/beam/sdk/values/TypeParameter.java @@ -0,0 +1,45 @@ +package org.apache.beam.sdk.values; + +import static com.google.common.base.Preconditions.checkArgument; + +import java.lang.reflect.ParameterizedType; +import java.lang.reflect.Type; +import java.lang.reflect.TypeVariable; + +/** + * Captures a free type variable that can be used in {@link TypeDescriptor#where}. For example: + * + * <pre> {@code + * static <T> TypeDescriptor<List<T>> listOf(Class<T> elementType) { + * return new TypeDescriptor<List<T>>() {} + * .where(new TypeParameter<T>() {}, elementType); + * }}</pre> + */ +public abstract class TypeParameter<T> { + final TypeVariable<?> typeVariable; + + public TypeParameter() { + Type superclass = getClass().getGenericSuperclass(); + checkArgument(superclass instanceof ParameterizedType, "%s isn't parameterized", superclass); + typeVariable = (TypeVariable<?>) ((ParameterizedType) superclass).getActualTypeArguments()[0]; + } + + @Override + public int hashCode() { + return typeVariable.hashCode(); + } + + @Override + public boolean equals(Object obj) { + if (!(obj instanceof TypeParameter)) { + return false; + } + TypeParameter<?> that = (TypeParameter<?>) obj; + return typeVariable.equals(that.typeVariable); + } + + @Override + public String toString() { + return typeVariable.toString(); + } +} http://git-wip-us.apache.org/repos/asf/incubator-beam/blob/699075e2/sdks/java/core/src/test/java/org/apache/beam/sdk/values/TypeDescriptorTest.java ---------------------------------------------------------------------- diff --git a/sdks/java/core/src/test/java/org/apache/beam/sdk/values/TypeDescriptorTest.java b/sdks/java/core/src/test/java/org/apache/beam/sdk/values/TypeDescriptorTest.java index 39472f9..a9b44b7 100644 --- a/sdks/java/core/src/test/java/org/apache/beam/sdk/values/TypeDescriptorTest.java +++ b/sdks/java/core/src/test/java/org/apache/beam/sdk/values/TypeDescriptorTest.java @@ -194,4 +194,16 @@ public class TypeDescriptorTest { new TypeToken<List<Set<String>>>() {}.getType(), rememberer.descriptorByInstance.getType()); } + + @Test + public void testWhere() throws Exception { + useWhereMethodToDefineTypeParam(new TypeDescriptor<String>() {}); + } + + private <T> void useWhereMethodToDefineTypeParam(TypeDescriptor<T> parameterType) { + TypeDescriptor<Set<T>> typeDescriptor = new TypeDescriptor<Set<T>>() {}.where( + new TypeParameter<T>() {}, parameterType); + assertEquals(new TypeToken<Set<String>>() {}.getType(), + typeDescriptor.getType()); + } }
