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| */ | |
| /** | |
| * Types and hierarchies of packages comprising a {@index "Java language | |
| * model"}, a reflective API that models the declarations and types of the Java | |
| * programming language. | |
| * | |
| * The members of this package and its subpackages are for use in | |
| * language modeling and language processing tasks and APIs including, | |
| * but not limited to, the {@linkplain javax.annotation.processing | |
| * annotation processing} framework. | |
| * | |
| * <p> This language model follows a <i>mirror</i>-based design; see | |
| * | |
| * <blockquote> | |
| * Gilad Bracha and David Ungar. <cite>Mirrors: Design Principles for | |
| * Meta-level Facilities of Object-Oriented Programming Languages</cite>. | |
| * In Proc. of the ACM Conf. on Object-Oriented Programming, Systems, | |
| * Languages and Applications, October 2004. | |
| * </blockquote> | |
| * | |
| * In particular, the model makes a distinction between declared | |
| * language constructs, like the {@linkplain javax.lang.model.element | |
| * element} representing {@code java.util.Set}, and the family of | |
| * {@linkplain javax.lang.model.type types} that may be associated | |
| * with an element, like the raw type {@code java.util.Set}, {@code | |
| * java.util.Set<String>}, and {@code java.util.Set<T>}. | |
| * | |
| * <p>Unless otherwise specified, methods in this package will throw | |
| * a {@code NullPointerException} if given a {@code null} argument. | |
| * | |
| * <h2><a id=elementsAndTypes>Elements and Types</a></h2> | |
| * | |
| * <h3><a id=DefUse>Definitions and Uses</a></h3> | |
| * | |
| * In broad terms the {@link javax.lang.model.element element} package | |
| * models the declarations, that is the <em>definitions</em>, of elements while | |
| * the {@link javax.lang.model.type type} package models <em>uses</em> | |
| * of types. In general, distinct uses can have individualized | |
| * information separate from the information associated with the | |
| * definition. In some sense, the information in the definition is | |
| * shared by all the uses. | |
| * <p>For example, consider the uses of {@code | |
| * java.lang.String} in the string processing method {@code | |
| * identityOrEmpty} below: | |
| * | |
| * {@snippet lang=java : | |
| * // Return the argument if it is non-null and the empty string otherwise. | |
| * public static @DefinitelyNotNull String identityOrEmpty(@MightBeNull String argument) { | |
| * ... | |
| * } | |
| * } | |
| * | |
| * The return type of the method is a {@code String} annotated with | |
| * a {@code @DefinitelyNotNull} type annotation while the type of | |
| * the parameter is a {@code String} annotated with a {@code | |
| * @MightBeNull} type annotation. In a reflective API, since the set | |
| * of annotations is different for the two <em>uses</em> of {@code | |
| * String} as a type, the return type and argument type would need to | |
| * be represented by different objects to distinguish between these two | |
| * cases. The <em>definition</em> of {@code java.lang.String} itself | |
| * is annotated with neither of the type annotations in question. | |
| * | |
| * <p>Another example, consider the declaration of the generic | |
| * interface (JLS {@jls 9.1.2}) {@code java.util.Set} which has one | |
| * type parameter. This declaration captures commonality between the | |
| * many parameterized types (JLS {@jls 4.5}) derived from that | |
| * declaration such as {@code java.util.Set<String>}, {@code | |
| * java.util.Set<E>}, {@code java.util.Set<?>}, and also the raw type | |
| * (JLS {@jls 4.8}) {@code java.util.Set}. | |
| * | |
| * <h3><a id=elementTypeMapping>Mapping between Elements and Types</a></h3> | |
| * | |
| * While distinct concepts, there are bidirectional (partial) mappings | |
| * between elements and types, between definitions and uses. For | |
| * example, roughly speaking, information that would be invariant for | |
| * all uses of a type can be retrieved from the element defining a | |
| * type. For example, consider a {@link | |
| * javax.lang.model.type.DeclaredType DeclaredType} type mirror | |
| * modeling a use of {@code java.lang.String}. Calling {@link | |
| * javax.lang.model.type.DeclaredType#asElement()} would return the | |
| * {@link javax.lang.model.element.TypeElement} for {@code | |
| * java.lang.String}. From the {@code TypeElement}, common information | |
| * such as {@linkplain | |
| * javax.lang.model.element.TypeElement#getSimpleName() name} and | |
| * {@linkplain javax.lang.model.element.TypeElement#getModifiers() | |
| * modifiers} can be retrieved. | |
| * | |
| * <p>All elements can be {@linkplain | |
| * javax.lang.model.element.Element#asType() mapped to} some type. | |
| * The elements for classes and interfaces get {@linkplain | |
| * javax.lang.model.element.TypeElement#asType() mapped to} a | |
| * {@linkplain javax.lang.model.element.TypeElement#asType() prototypical type}. | |
| * Conversely, in general, many types can map to the same | |
| * {@linkplain javax.lang.model.element.TypeElement type element}. For | |
| * example, the type mirror for the raw type {@code java.util.Set}, | |
| * the prototypical type {@code java.util.Set<E>}, and the type {@code | |
| * java.util.Set<String>} would all {@linkplain | |
| * javax.lang.model.type.DeclaredType#asElement() map to} the type | |
| * element for {@code java.util.Set}. Several kinds of types can be | |
| * mapped to elements, but other kinds of types do <em>not</em> have | |
| * an {@linkplain javax.lang.model.util.Types#asElement(TypeMirror) | |
| * element mapping}. For example, the type mirror of an {@linkplain | |
| * javax.lang.model.type.ExecutableType executable type} does | |
| * <em>not</em> have an element mapping while a {@linkplain | |
| * javax.lang.model.type.DeclaredType declared type} would map to a | |
| * {@linkplain javax.lang.model.element.TypeElement type element}, as | |
| * discussed above. | |
| * | |
| * @since 1.6 | |
| * | |
| * @see <a href="https://jcp.org/en/jsr/detail?id=269"> | |
| * JSR 269: Pluggable Annotation Processing API</a> | |
| */ | |
| package javax.lang.model; |