理解“TypeElement'和'的declaredType”在Java接口 [英] Understanding 'TypeElement' and 'DeclaredType' interface in java

问题描述

这两个接口的一个用途，就是写注释处理器。

One usage of these two interface, is to write annotation processor.

作为Java初学者，我发现，是由这两个包加间接的水平：
javax.lang.model.element中的＆安培; javax.lang.model.type中来提供关于Java 接口和java 类混乱。

As a java beginner, I find the level of indirection that is added by these two packages: javax.lang.model.element & javax.lang.model.type to provide metadata about java interface and java class confusing.

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Java的文档注释说，

java doc comments say,

TypeElement 重新presents一个类或接口程序元素。提供对有关类型及其成员的信息。请注意，枚举
  类型是一种类和注释类型是一种接口。

TypeElement represents a class or interface program element. Provides access to information about the type and its members. Note that an enum type is a kind of class and an annotation type is a kind of interface.

的declaredType 重新presents一个声明类型，是一个类键入或接口类型。这包括参数化类型，如 java.util.Set中的＆LT;弦乐方式＆gt; 以及原始类型

DeclaredType represents a declared type, either a class type or an interface type. This includes parameterized types such as java.util.Set<String> as well as raw types.

两者之间的区别：

而在 TypeElement 重新presents一个类或接口的元素的一个的declaredType 重新presents一个类或接口的键入的，后者是使用（或调用的）前的。

While a TypeElement represents a class or interface element, a DeclaredType represents a class or interface type, the latter being a use (or invocation) of the former.

我如何区分行话的元素的距离的键入的？例如：如何为类的元素的从类不同的键入？请帮我用一个例子。

How do I differentiate the jargon element from type? For example: How is class element different from class type? Please help me with an example.

推荐答案

的元素的是，你用它来组成一个软件部分，即 ExecutableElement ■哪些，顾名思义，包含可执行code，它描述了一种存储 VariableElement 和 TypeElement ■哪些合计持有这些。这是Java编程语言的一个特殊属性（如面向对象的语言），有没有顶级的功能，也没有全局变量没有 TypeElement ，它们被定义的。

The elements are the parts that you use to compose a software, i.e. ExecutableElements which, as the name suggests, contain executable code, VariableElements which describe a kind of storage and TypeElements which hold these together. It’s a special property of the Java programming language (as an object oriented language) that there are no top-level functions nor global variables without a TypeElement, in which they are defined.

在换句话说，如果你写一个Java程序，你将永远有含有至少一种类型声明至少有一个的.java 源文件。这 TypeElement 将有可能至少包含一个 ExecutableElement 来弥补一个有用的软件。在 TypeElement 可以包含多个 ExecutableElement S， VariableElement 和嵌套 TypeElement 秒。这是你的程序的结构的

In other words, if you write a Java program, you will always have at least one .java source file containing at least one type declaration. That TypeElement will likely contain at least one ExecutableElement to make up a useful software. The TypeElement may contain multiple ExecutableElements, VariableElements and nested TypeElements. That’s the structure of your program.

A 键入的是，只要你声明成员或局部变量，你使用的东西，同时也宣告一个超类或-interface时。但是，让我们关注的变量，以更好地理解：

A type is something which you use whenever you declare a member or local variable, but also when declaring a super class or -interface. But let’s focus on variables, for a better understanding:

一个变量可以有一个原语类型，这是固有的编程语言，它也可以有一个类型，其存在是隐含的，例如当有键入 X ，你也可以使用数组类型 X [] 在一个变量声明，但只在声明类型的是必须有相应的 TypeElement ，再presenting的东西，开发商写（或已生成的类型一个工具）。泛型还允许您撰写的类型，例如声明类型的变量设置 - LT ;?扩展号码＆GT; ，而设置和编号的声明类型的已相应的程序元素...

A variable can have a primitive type, which is intrinsic to the programming language, it can also have a type whose existence is implied, e.g. when there is a type X, you can also use the array type X[] in a variable declaration, but only the declared type is a type which must have a corresponding TypeElement, representing something, a developer has written (or has been generated by a tool). Generics also allow you to compose types, e.g. declare a variable of type Set<? extends Number> whereas Set and Number are declared types which have corresponding program elements…

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