TypeReference.java

TypeReference.java

// Copyright (c) Microsoft Corporation. All rights reserved. // Licensed under the MIT License. package com.azure.core.util.serializer; import com.azure.core.util.logging.ClientLogger; import java.lang.reflect.ParameterizedType; import java.lang.reflect.Type; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; /** * This class represents a generic Java type, retaining information about generics. * * <p><strong>Code sample</strong></p> * * {@codesnippet com.azure.core.util.serializer.constructor} * * {@codesnippet com.azure.core.util.serializer.createInstance#class} * * @param <T> The type being represented. */ public abstract class TypeReference<T> {  private static final ClientLogger LOGGER = new ClientLogger(TypeReference.class); private static final String MISSING_TYPE = "Type constructed without type information.";  private static final Map<Class<?>, TypeReference<?>> CACHE = new ConcurrentHashMap<>(); private final Type javaType; /** * Constructs a new {@link TypeReference} which maintains generic information. * * @throws IllegalArgumentException If the reference is constructed without type information. */  public TypeReference() {  Type superClass = this.getClass().getGenericSuperclass();  if (superClass instanceof Class) {  throw LOGGER.logExceptionAsError(new IllegalArgumentException(MISSING_TYPE)); } else {  this.javaType = ((ParameterizedType) superClass).getActualTypeArguments()[0]; }  }  private TypeReference(Class<T> clazz) {  this.javaType = clazz;  } /** * Returns the {@link Type} representing {@code T}. * * @return The {@link Type} representing {@code T}. */ public Type getJavaType() {  return javaType; } /** * Creates and instance of {@link TypeReference} which maintains the generic {@code T} of the passed {@link Class}. * <p> * This method will cache the instance of {@link TypeReference} using the passed {@link Class} as the key. This is * meant to be used with non-generic types such as primitive object types and POJOs, not {@code Map<String, Object>} * or {@code List<Integer>} parameterized types. * * @param clazz {@link Class} that contains generic information used to create the {@link TypeReference}. * @param <T> The generic type. * @return Either the cached or new instance of {@link TypeReference}. */ @SuppressWarnings("unchecked") public static <T> TypeReference<T> createInstance(Class<T> clazz) { /* * When computing the TypeReference if the key is absent ignore the parameter from the compute function. The * compute function wildcards to T type which causes the type system to breakdown. */  return (TypeReference<T>) CACHE.computeIfAbsent(clazz, c -> new TypeReference<T>(clazz) { }); } } 

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