author | ddehaven |
Fri, 16 Dec 2016 11:58:18 -0800 | |
changeset 42836 | 1d55dcc9a118 |
parent 41514 | a75c2b869d8d |
child 43770 | a321bed02000 |
permissions | -rw-r--r-- |
33362 | 1 |
/* |
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* Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. Oracle designates this |
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* particular file as subject to the "Classpath" exception as provided |
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* by Oracle in the LICENSE file that accompanied this code. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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*/ |
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/** |
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* Provides interfaces for creating tools, such as a Read-Eval-Print Loop (REPL), |
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* which interactively evaluate "snippets" of Java programming language code. |
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* Where a "snippet" is a single expression, statement, or declaration. |
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* This functionality can be used to enhance tools such as IDEs or can be |
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* stand-alone. |
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* <p> |
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* {@link jdk.jshell.JShell} is the central class. An instance of |
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* <code>JShell</code> holds the evaluation state, which is both the current |
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* set of source snippets and the execution state they have produced. |
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* <p> |
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* Each source snippet is represented by an instance of a subclass of |
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* {@link jdk.jshell.Snippet}. For example, a statement is represented by an |
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* instance of {@link jdk.jshell.StatementSnippet}, and a method declaration is |
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* represented by an instance of {@link jdk.jshell.MethodSnippet}. |
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* Snippets are created when |
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* {@link jdk.jshell.JShell#eval(java.lang.String) JShell.eval(String)} |
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* is invoked with an input which includes one or more snippets of code. |
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* <p> |
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* Any change to the compilation status of a snippet is reported with a |
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* {@link jdk.jshell.SnippetEvent}. There are three major kinds of |
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* changes to the status of a snippet: it can created with <code>eval</code>, |
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* it can be dropped from the active source state with |
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* {@link jdk.jshell.JShell#drop(jdk.jshell.Snippet)}, and it can have |
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* its status updated as a result of a status change in another snippet. |
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* For |
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* example: given <code>js</code>, an instance of <code>JShell</code>, executing |
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* <code>js.eval("int x = 5;")</code> will add the variable <code>x</code> to |
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* the source state and will generate an event describing the creation of a |
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* {@link jdk.jshell.VarSnippet} for <code>x</code>. Then executing |
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* <code>js.eval("int timesx(int val) { return val * x; }")</code> will add |
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* a method to the source state and will generate an event |
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* describing the creation of a {@link jdk.jshell.MethodSnippet} for |
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* <code>timesx</code>. |
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* Assume that <code>varx</code> holds the snippet created by the first |
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* call to <code>eval</code>, executing <code>js.drop(varx)</code> will |
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* generate two events: one for changing the status of the |
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* variable snippet to <code>DROPPED</code> and one for |
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* updating the method snippet (which now has an unresolved reference to |
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* <code>x</code>). |
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* <p> |
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* Of course, for any general application of the API, the input would not be |
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* fixed strings, but would come from the user. Below is a very simplified |
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* example of how the API might be used to implement a REPL. |
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* <pre> |
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* {@code |
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* import java.io.ByteArrayInputStream; |
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* import java.io.Console; |
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* import java.util.List; |
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* import jdk.jshell.*; |
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* import jdk.jshell.Snippet.Status; |
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* |
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* class ExampleJShell { |
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* public static void main(String[] args) { |
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* Console console = System.console(); |
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* try (JShell js = JShell.create()) { |
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* do { |
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* System.out.print("Enter some Java code: "); |
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* String input = console.readLine(); |
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* if (input == null) { |
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* break; |
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* } |
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* List<SnippetEvent> events = js.eval(input); |
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* for (SnippetEvent e : events) { |
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* StringBuilder sb = new StringBuilder(); |
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* if (e.causeSnippet == null) { |
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* // We have a snippet creation event |
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* switch (e.status) { |
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* case VALID: |
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* sb.append("Successful "); |
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* break; |
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* case RECOVERABLE_DEFINED: |
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* sb.append("With unresolved references "); |
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* break; |
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* case RECOVERABLE_NOT_DEFINED: |
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* sb.append("Possibly reparable, failed "); |
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* break; |
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* case REJECTED: |
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* sb.append("Failed "); |
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* break; |
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* } |
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* if (e.previousStatus == Status.NONEXISTENT) { |
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* sb.append("addition"); |
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* } else { |
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* sb.append("modification"); |
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* } |
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* sb.append(" of "); |
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* sb.append(e.snippet.source()); |
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* System.out.println(sb); |
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* if (e.value != null) { |
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* System.out.printf("Value is: %s\n", e.value); |
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* } |
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* System.out.flush(); |
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* } |
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* } |
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* } while (true); |
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* } |
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* System.out.println("\nGoodbye"); |
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* } |
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* } |
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* } |
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* </pre> |
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* <p> |
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* To register for status change events use |
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* {@link jdk.jshell.JShell#onSnippetEvent(java.util.function.Consumer)}. |
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* These events are only generated by <code>eval</code> and <code>drop</code>, |
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* the return values of these methods are the list of events generated by that |
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* call. So, as in the example above, events can be used without registering |
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* to receive events. |
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* <p> |
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* If you experiment with this example, you will see that failing to terminate |
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* a statement or variable declaration with a semi-colon will simply fail. |
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* An unfinished entry (for example a desired multi-line method) will also just |
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* fail after one line. The utilities in {@link jdk.jshell.SourceCodeAnalysis} |
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* provide source boundary and completeness analysis to address cases like |
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* those. <code>SourceCodeAnalysis</code> also provides suggested completions |
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* of input, as might be used in tab-completion. |
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*/ |
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package jdk.jshell; |
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