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43 package net.java.html.js;
45 import java.lang.annotation.ElementType;
46 import java.lang.annotation.Retention;
47 import java.lang.annotation.RetentionPolicy;
48 import java.lang.annotation.Target;
50 /** Put this annotation on a method to provide its special implementation
51 * in JavaScript. This is a way to define <em>native</em> methods that
52 * interact with the surrounding JavaScript environment. Check the list
53 * <a href="package-summary.html">use-cases</a> to see real world
54 * use of this annotation.
56 * Visit an <a target="_blank" href="http://dew.apidesign.org/dew/#7102188">on-line demo</a>
57 * to play with {@link JavaScriptBody} annotation for real.
59 * @author Jaroslav Tulach
61 @Retention(RetentionPolicy.CLASS)
62 @Target({ ElementType.METHOD, ElementType.CONSTRUCTOR })
63 public @interface JavaScriptBody {
64 /** Names of parameters for the method generated method that can
65 * be referenced from {@link #body()}.
67 * @return array of the names of parameters for the method
70 public String[] args();
72 /** The actual body of the method in JavaScript. This string will be
73 * put into generated header (last character is '{') and footer (e.g. '}').
74 * The body can reference provided arguments. In case of non-static
75 * instance method it may reference <code>this</code>.
77 * @return JavaScript body of a function which can access {@link #args()} and possibly
82 /** Should a special syntax for calling back into Java object be turned on?
83 * The syntax begins with <b>{@code @}</b> followed by fully qualified
84 * package name of the class. Now followed by <b>::</b> and a method in
85 * the class followed by its parameters enclosed inside <b>(...)</b>.
86 * This is the syntax one can use to call <code>run()</code>
87 * method of {@link Runnable}:
88 * <pre>r.@java.lang.Runnable::run()()</pre>.
89 * One can also call static methods. Just use:
90 * <pre>var ten = @java.lang.Integer::parseInt(Ljava/lang/String;)("10")</pre>
92 * @return true, if the script should be scanned for special callback
95 public boolean javacall() default false;
97 /** Should we wait before the JavaScript snippet execution finishes?
100 * Some implementations that recognize the {@link JavaScriptBody} annotation
101 * need to reschedule the JavaScript execution into different thread and
102 * then it is easier for them to perform the execution asynchronously
103 * and not wait for the result of the execution. This may however be
104 * unexpected (for example when one awaits a callback into Java)
105 * and as such it has to be explicitly allowed by specifying
106 * <code>wait4js = false</code>. Such methods need to return <code>void</code>.
108 * Implementations that execute the JavaScript synchronously may ignore
111 * Implementations that delay execution of JavaScript need to guarantee
112 * the order of snippets. Those that were submitted sooner, need to be
113 * executed sooner. Each snippet need to be executed in a timely manner
114 * (e.g. by a second, or so) even if there are no other calls made
115 * in the main program.
119 * @return <code>false</code> in case one allows asynchronous execution
120 * of the JavaScript snippet
122 public boolean wait4js() default true;
124 /** Controls garbage collection behavior of method parameters.
125 * In general JavaScript garbage
126 * collection system makes it close to impossible to find out whether
127 * an object is supposed to be still used or not. Some systems have
128 * an external hooks to find that out (like <em>JavaFX</em> <code>WebView</code>),
129 * in some systems this information is not important (like the
130 * <a href="http://bck2brwsr.apidesign.org">Bck2Brwsr</a> VM running
131 * all in JavaScript), but other execution systems just can't find that
132 * out. To prevent memory leaks on such systems and help them manage
133 * memory more effectively, those who define JavaScript interfacing
134 * methods may indicate whether the non-primitive parameters passed
135 * in should be hold only for the time of method invocation or
136 * for the whole application lifetime.
138 * The default value is <code>true</code> as that is compatible with
139 * previous behavior and also prevents unwanted surprises when something
140 * garbage collects pre-maturaly. Framework developers are however
141 * encouraged to use <code>keepAlive=false</code> as much as possible.
143 * @return whether Java objects passed as parameters of the method
144 * should be made guaranteed to be available JavaScript
145 * even after the method invocation is over (e.g. prevent them to be
146 * garbage collected in Java until it is known they are not needed
147 * from JavaScript at all).
151 public boolean keepAlive() default true;