1 /*
2 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package jdk.jshell.spi;
27
28 import java.util.Collection;
29 import jdk.jshell.JShellException;
30
31 /**
32 * This interface specifies the functionality that must provided to implement
33 * a pluggable JShell execution engine.
34 * <p>
35 * The audience for this Service Provider Interface is engineers
36 * wishing to implement their own version of the execution engine in support
37 * of the JShell API. This is NOT a part of the JShell API.
38 * <p>
39 * A Snippet is compiled into code wrapped in a 'wrapper class'. The execution
40 * engine is used by the core JShell implementation to load and, for
41 * executable Snippets, execute the Snippet.
42 * <p>
43 * Methods defined in this interface should only be called by the core JShell
44 * implementation.
45 * <p>
46 * To install an instance of ExecutionControl, it is passed to
47 * {@link jdk.jshell.JShell.Builder#executionEngine(jdk.jshell.spi.ExecutionControl) }.
48 */
49 public interface ExecutionControl {
50
51 /**
52 * Represents the current status of a class in the execution engine.
53 */
54 public enum ClassStatus {
55 /**
56 * Class is not known to the execution engine (not loaded).
57 */
58 UNKNOWN,
59
60 /**
61 * Class is loaded, but the loaded/redefined bytes do not match those
62 * returned by {@link ExecutionEnv#getClassBytes(java.lang.String) }.
63 */
64 NOT_CURRENT,
65
66 /**
67 * Class is loaded and loaded/redefined bytes match those
68 * returned by {@link ExecutionEnv#getClassBytes(java.lang.String) }.
69 */
70 CURRENT
71 };
72
73 /**
74 * Initializes the instance. No methods in this interface can be called
75 * before this.
76 *
77 * @param env the execution environment information provided by JShell
78 * @throws Exception if the instance is unable to initialize
79 */
80 void start(ExecutionEnv env) throws Exception;
81
82 /**
83 * Shuts down this execution engine. Implementation should free all
84 * resources held by this execution engine.
85 * <p>
86 * No calls to methods on this interface should be made after close.
87 */
88 void close();
89
90 /**
91 * Adds the path to the execution class path.
92 *
93 * @param path the path to add
94 * @return true if successful
95 */
96 boolean addToClasspath(String path);
97
98 /**
99 * Invokes an executable Snippet by calling a method on the specified
100 * wrapper class. The method must have no arguments and return String.
101 *
102 * @param classname the class whose method should be invoked
103 * @param methodname the name of method to invoke
104 * @return the result of the execution or null if no result
105 * @throws JShellException if a user exception if thrown,
106 * {@link jdk.jshell.EvalException EvalException} will be thrown; if an
107 * unresolved reference is encountered,
108 * {@link jdk.jshell.UnresolvedReferenceException UnresolvedReferenceException}
109 * will be thrown
110 */
111 String invoke(String classname, String methodname) throws JShellException;
112
113 /**
114 * Attempts to load new classes. Class bytes are retrieved from
115 * {@link ExecutionEnv#getClassBytes(java.lang.String) }
116 *
117 * @param classes list of class names to load
118 * @return true if load succeeded
119 */
120 boolean load(Collection<String> classes);
121
122 /**
123 * Attempts to redefine previously loaded classes. Class bytes are retrieved
124 * from {@link ExecutionEnv#getClassBytes(java.lang.String) }
125 *
126 * @param classes list of class names to redefine
127 * @return true if redefine succeeded
128 */
129 boolean redefine(Collection<String> classes);
130
131 /**
132 * Queries if the class is loaded and the class bytes are current.
133 *
134 * @param classname name of the wrapper class to query
135 * @return {@code UNKNOWN} if the class is not loaded; {@code CURRENT} if
136 * the loaded/redefined bytes are equal to the most recent bytes for this
137 * wrapper class; otherwise {@code NOT_CURRENT}
138 */
139 ClassStatus getClassStatus(String classname);
140
141 /**
142 * Interrupt a running invoke.
143 */
144 void stop();
145
146 /**
147 * Returns the value of a variable.
148 *
149 * @param classname the name of the wrapper class of the variable
150 * @param varname the name of the variable
151 * @return the value of the variable
152 */
153 String varValue(String classname, String varname);
154 }