已阅读 次

Java Script Engine

文章目录

  1. 1. Java Script Engine

Java Script Engine

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
public static void main(String[] agrs) throws ScriptException {
    final ScriptEngine javascriptEngine = new ScriptEngineManager().getEngineByName("javascript");
    final Bindings globalBindings = javascriptEngine.getBindings(ScriptContext.GLOBAL_SCOPE);
    globalBindings.put("a", 5);
    System.out.println("-------Engine bindings scope--------------");
    final Bindings javascriptEngineBindings = javascriptEngine.getBindings(ScriptContext.ENGINE_SCOPE);
    javascriptEngineBindings.put("x", 20);
    javascriptEngineBindings.put("y", 20.4);
    javascriptEngineBindings.put("z", 1);
    final String[] scriptArray = {"x*y+z", "x*(y+z)", "a+x*(y+z)"};
    eval(scriptArray, javascriptEngine);

    System.out.println("-------Local bindings scope--------------");
    final Bindings localBinding = javascriptEngine.createBindings();
    localBinding.put("x", 2);
    localBinding.put("y", 3);
    localBinding.put("z", 1);
    eval(scriptArray, javascriptEngine, localBinding);
}

private static void eval(String[] scriptArray, ScriptEngine javascriptEngine) throws ScriptException {
    Bindings aBindings = javascriptEngine.getBindings(ScriptContext.GLOBAL_SCOPE);
    for (String key : aBindings.keySet()) {
        System.out.println("Args (Global bindings scope) > " + key + "=" + aBindings.get(key));
    }
    aBindings = javascriptEngine.getBindings(ScriptContext.ENGINE_SCOPE);
    for (String key : aBindings.keySet()) {
        System.out.println("Args (Engine bindings scope) > " + key + "=" + aBindings.get(key));
    }
    for (String script : scriptArray) {
        System.out.println("script > " + script + " = " + javascriptEngine.eval(script));
    }
}

private static void eval(String[] scriptArray, ScriptEngine javascriptEngine, Bindings localBinding) throws ScriptException {
    Bindings aBindings = javascriptEngine.getBindings(ScriptContext.GLOBAL_SCOPE);
    for (String key : aBindings.keySet()) {
        System.out.println("Args (Global bindings scope) > " + key + "=" + aBindings.get(key));
    }
    aBindings = javascriptEngine.getBindings(ScriptContext.ENGINE_SCOPE);
    for (String key : aBindings.keySet()) {
        System.out.println("Args (Engine bindings scope) > " + key + "=" + aBindings.get(key));
    }
    for (String s : localBinding.keySet()) {
        System.out.println("Args (Local bindings scope) > " + s + "=" + aBindings.get(s));
    }
    for (String script : scriptArray) {
        System.out.println("script > " + script + " = " + javascriptEngine.eval(script, localBinding));
    }
}

输出结果：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
-------Engine bindings scope--------------
Args (Global bindings scope) > a=5
Args (Engine bindings scope) > z=1
Args (Engine bindings scope) > y=20.4
Args (Engine bindings scope) > x=20
script > x*y+z = 409.0
script > x*(y+z) = 428.0
script > a+x*(y+z) = 433.0
-------Local bindings scope--------------
Args (Global bindings scope) > a=5
Args (Engine bindings scope) > println=sun.org.mozilla.javascript.internal.InterpretedFunction@45a23f67
Args (Engine bindings scope) > context=javax.script.SimpleScriptContext@1ef0a6e8
Args (Engine bindings scope) > z=1
Args (Engine bindings scope) > print=sun.org.mozilla.javascript.internal.InterpretedFunction@495dd936
Args (Engine bindings scope) > y=20.4
Args (Engine bindings scope) > x=20
Args (Local bindings scope) > z=1
Args (Local bindings scope) > y=20.4
Args (Local bindings scope) > x=20
script > x*y+z = 7.0
script > x*(y+z) = 8.0
script > a+x*(y+z) = 13.0

Process finished with exit code 0

Bindings变量的有效范围

  1. Global对应到ScriptEngineFactory，通过scriptEngine.getBindings(ScriptContext.GLOBAL_SCOPE)获得。
  2. Engine对应到ScriptEngine，通过scriptEngine.getBindings(ScriptContext.ENGINE_SCOPE)获得。
  3. Local Binding每一次执行script，通过scriptEngine.createBindings()获得。

使用场景适用于

  1. 规则引擎
  2. 流程流转条件判定

观点仅代表自己，期待你的留言。