ElementKindVisitor6.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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package javax.lang.model.util;

import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.Element;
import javax.lang.model.element.ElementKind;
import javax.lang.model.element.ExecutableElement;
import javax.lang.model.element.PackageElement;
import javax.lang.model.element.TypeElement;
import javax.lang.model.element.TypeParameterElement;
import javax.lang.model.element.VariableElement;

import static javax.lang.model.SourceVersion.RELEASE_6;
import static javax.lang.model.element.ElementKind.PACKAGE;
import static javax.lang.model.element.ElementKind.TYPE_PARAMETER;


/**
 * A visitor of program elements based on their {@linkplain
 * ElementKind kind} with default behavior appropriate for the {@link
 * SourceVersion#RELEASE_6 RELEASE_6} source version.  For {@linkplain
 * Element elements} <code><i>Xyz</i></code> that may have more than one
 * kind, the <code>visit<i>Xyz</i></code> methods in this class delegate
 * to the <code>visit<i>Xyz</i>As<i>Kind</i></code> method corresponding to the
 * first argument's kind.  The <code>visit<i>Xyz</i>As<i>Kind</i></code> methods
 * call {@link #defaultAction defaultAction}, passing their arguments
 * to {@code defaultAction}'s corresponding parameters.
 *
 * <p> Methods in this class may be overridden subject to their
 * general contract.  Note that annotating methods in concrete
 * subclasses with {@link java.lang.Override @Override} will help
 * ensure that methods are overridden as intended.
 *
 * <p> <b>WARNING:</b> The {@code ElementVisitor} interface
 * implemented by this class may have methods added to it or the
 * {@code ElementKind} {@code enum} used in this case may have
 * constants added to it in the future to accommodate new, currently
 * unknown, language structures added to future versions of the
 * Java&trade; programming language.  Therefore, methods whose names
 * begin with {@code "visit"} may be added to this class in the
 * future; to avoid incompatibilities, classes which extend this class
 * should not declare any instance methods with names beginning with
 * {@code "visit"}.
 *
 * <p>When such a new visit method is added, the default
 * implementation in this class will be to call the {@link
 * #visitUnknown visitUnknown} method.  A new abstract element kind
 * visitor class will also be introduced to correspond to the new
 * language level; this visitor will have different default behavior
 * for the visit method in question.  When the new visitor is
 * introduced, all or portions of this visitor may be deprecated.
 *
 * @param <R> the return type of this visitor's methods.  Use {@link
 *            Void} for visitors that do not need to return results.
 * @param <P> the type of the additional parameter to this visitor's
 *            methods.  Use {@code Void} for visitors that do not need an
 *            additional parameter.
 *
 * @author Joseph D. Darcy
 * @author Scott Seligman
 * @author Peter von der Ah&eacute;
 * @see ElementKindVisitor7
 * @see ElementKindVisitor8
 * @see ElementKindVisitor9
 * @since 1.6
 */
// 元素访问器的细化版本，会进行类型校验，以及对某些粗放的类型进行细化后再访问（JDK6）
@SupportedSourceVersion(RELEASE_6)
public class ElementKindVisitor6<R, P> extends SimpleElementVisitor6<R, P> {
    /**
     * Constructor for concrete subclasses; uses {@code null} for the
     * default value.
     *
     * @deprecated Release 6 is obsolete; update to a visitor for a newer
     * release level.
     */
    @Deprecated(since = "9")
    protected ElementKindVisitor6() {
        super(null);
    }
    
    /**
     * Constructor for concrete subclasses; uses the argument for the
     * default value.
     *
     * @param defaultValue the value to assign to {@link #DEFAULT_VALUE}
     *
     * @deprecated Release 6 is obsolete; update to a visitor for a newer
     * release level.
     */
    @Deprecated(since = "9")
    protected ElementKindVisitor6(R defaultValue) {
        super(defaultValue);
    }
    
    /**
     * {@inheritDoc}
     *
     * The element argument has kind {@code PACKAGE}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     *
     * @return {@inheritDoc}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     */
    // 访问包元素
    @Override
    public R visitPackage(PackageElement e, P p) {
        assert e.getKind() == PACKAGE : "Bad kind on PackageElement";
        return defaultAction(e, p);
    }
    
    /**
     * {@inheritDoc}
     *
     * The element argument has kind {@code TYPE_PARAMETER}.
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     *
     * @return {@inheritDoc}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     */
    // 访问类型参数
    @Override
    public R visitTypeParameter(TypeParameterElement e, P p) {
        assert e.getKind() == TYPE_PARAMETER : "Bad kind on TypeParameterElement";
        return defaultAction(e, p);
    }
    
    /**
     * {@inheritDoc}
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     *
     * @return the result of the kind-specific visit method
     *
     * @implSpec This implementation dispatches to the visit method for the
     * specific {@linkplain ElementKind kind} of type, {@code
     * ANNOTATION_TYPE}, {@code CLASS}, {@code ENUM}, or {@code
     * INTERFACE}.
     */
    // - 访问类/接口元素，这里要细化
    @Override
    public R visitType(TypeElement e, P p) {
        ElementKind k = e.getKind();
        switch(k) {
            case ANNOTATION_TYPE:
                return visitTypeAsAnnotationType(e, p);
            
            case CLASS:
                return visitTypeAsClass(e, p);
            
            case INTERFACE:
                return visitTypeAsInterface(e, p);
            
            case ENUM:
                return visitTypeAsEnum(e, p);
            
            default:
                throw new AssertionError("Bad kind " + k + " for TypeElement" + e);
        }
    }
    
    /**
     * Visits an {@code ANNOTATION_TYPE} type element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     */
    // -- 访问注解元素
    public R visitTypeAsAnnotationType(TypeElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits a {@code CLASS} type element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     */
    // -- 访问类元素
    public R visitTypeAsClass(TypeElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits an {@code INTERFACE} type element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     * .
     */
    // -- 访问接口元素
    public R visitTypeAsInterface(TypeElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits an {@code ENUM} type element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     */
    // -- 访问枚举元素
    public R visitTypeAsEnum(TypeElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits a variable element
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     *
     * @return the result of the kind-specific visit method
     *
     * @implSpec This implementation dispatches to the visit method for
     * the specific {@linkplain ElementKind kind} of variable, {@code
     * ENUM_CONSTANT}, {@code EXCEPTION_PARAMETER}, {@code FIELD},
     * {@code LOCAL_VARIABLE}, {@code PARAMETER}, or {@code RESOURCE_VARIABLE}.
     */
    // * 访问变量，这里要细化
    @Override
    public R visitVariable(VariableElement e, P p) {
        ElementKind k = e.getKind();
        switch(k) {
            case FIELD:
                return visitVariableAsField(e, p);
            
            case PARAMETER:
                return visitVariableAsParameter(e, p);
            
            case LOCAL_VARIABLE:
                return visitVariableAsLocalVariable(e, p);
            
            case ENUM_CONSTANT:
                return visitVariableAsEnumConstant(e, p);
            
            case EXCEPTION_PARAMETER:
                return visitVariableAsExceptionParameter(e, p);
            
            case RESOURCE_VARIABLE:
                return visitVariableAsResourceVariable(e, p);
            
            default:
                throw new AssertionError("Bad kind " + k + " for VariableElement" + e);
        }
    }
    
    /**
     * Visits a {@code FIELD} variable element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     * .
     */
    // ** 访问字段
    public R visitVariableAsField(VariableElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits a {@code PARAMETER} variable element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     */
    // ** 访问形参
    public R visitVariableAsParameter(VariableElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits a {@code LOCAL_VARIABLE} variable element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     */
    // ** 访问局部变量
    public R visitVariableAsLocalVariable(VariableElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits an {@code ENUM_CONSTANT} variable element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     * .
     */
    // ** 访问枚举常量
    public R visitVariableAsEnumConstant(VariableElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits an {@code EXCEPTION_PARAMETER} variable element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     * .
     */
    // ** 访问异常参数
    public R visitVariableAsExceptionParameter(VariableElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits a {@code RESOURCE_VARIABLE} variable element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code visitUnknown}
     *
     * @implSpec This implementation calls {@code visitUnknown}.
     * @since 1.7
     */
    // ** 访问资源参数
    public R visitVariableAsResourceVariable(VariableElement e, P p) {
        return visitUnknown(e, p);
    }
    
    /**
     * {@inheritDoc}
     *
     * @param e {@inheritDoc}
     * @param p {@inheritDoc}
     *
     * @return the result of the kind-specific visit method
     *
     * @implSpec This implementation dispatches to the visit method
     * for the specific {@linkplain ElementKind kind} of executable,
     * {@code CONSTRUCTOR}, {@code INSTANCE_INIT}, {@code METHOD}, or
     * {@code STATIC_INIT}.
     */
    // = 访问可执行类型，这里要细化
    @Override
    public R visitExecutable(ExecutableElement e, P p) {
        ElementKind k = e.getKind();
        switch(k) {
            case CONSTRUCTOR:
                return visitExecutableAsConstructor(e, p);
            
            case METHOD:
                return visitExecutableAsMethod(e, p);
            
            case INSTANCE_INIT:
                return visitExecutableAsInstanceInit(e, p);
            
            case STATIC_INIT:
                return visitExecutableAsStaticInit(e, p);
            
            default:
                throw new AssertionError("Bad kind " + k + " for ExecutableElement" + e);
        }
    }
    
    /**
     * Visits a {@code CONSTRUCTOR} executable element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     */
    // == 访问构造器
    public R visitExecutableAsConstructor(ExecutableElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits a {@code METHOD} executable element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     */
    // == 访问方法
    public R visitExecutableAsMethod(ExecutableElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits an {@code INSTANCE_INIT} executable element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     */
    // == 访问初始化块
    public R visitExecutableAsInstanceInit(ExecutableElement e, P p) {
        return defaultAction(e, p);
    }
    
    /**
     * Visits a {@code STATIC_INIT} executable element.
     *
     * @param e the element to visit
     * @param p a visitor-specified parameter
     *
     * @return the result of {@code defaultAction}
     *
     * @implSpec This implementation calls {@code defaultAction}.
     */
    // == 访问静态初始化块
    public R visitExecutableAsStaticInit(ExecutableElement e, P p) {
        return defaultAction(e, p);
    }
    
}