JDK1.6版添加了新的ScriptEngine類，允許用戶直接執行js代碼。

在Java中直接調用js代碼

不能調用瀏覽器中定義的js函數，會拋出異常提示ReferenceError:?“alert”?is?not?defined。

[java]?view plain?copy
package?com.sinaapp.manjushri;???
import?javax.script.ScriptEngine;???
import?javax.script.ScriptEngineManager;??
import?javax.script.ScriptException;???/**??*?直接調用js代碼??*/??
??????????
??public?class?ScriptEngineTest?{??????
????public?static?void?main(String[]?args)?{???
????????ScriptEngineManager?manager?=?new?ScriptEngineManager();??
????????ScriptEngine?engine?=?manager.getEngineByName("javascript");??
??????????try?{??????
????????????engine.eval("var?a=3;?var?b=4;print?(a+b);");??????
????????????//?不能調用瀏覽器中定義的js函數??????
????????????//?engine.eval("alert(\"js?alert\");");?????
????????????//?錯誤，會拋出alert引用不存在的異常?????
??????????}?catch?(ScriptException?e)?{??
??????????????e.printStackTrace();?????
??????????}????
??????}?????
}??

輸出結果：7

在Java中綁定js變量

在調用engine.get(key);時，如果key沒有定義，則返回null

[java]?view plain?copy
package?com.sinaapp.manjushri;?????
import?javax.script.Bindings;???
import?javax.script.ScriptContext;???
import?javax.script.ScriptEngine;???
import?javax.script.ScriptEngineManager;???
import?javax.script.ScriptException;?????
????????????
public?class?ScriptEngineTest2?{???
????public?static?void?main(String[]?args)?{?????
????????ScriptEngineManager?manager?=?new?ScriptEngineManager();?????
??????????ScriptEngine?engine?=?manager.getEngineByName("javascript");?????
??????????engine.put("a",?4);???engine.put("b",?3);?????
??????????Bindings?bindings?=?engine.getBindings(ScriptContext.ENGINE_SCOPE);??
??????????try?{??
??????????????//?只能為Double，使用Float和Integer會拋出異常??
??????????????Double?result?=?(Double)?engine.eval("a+b");??
??????????????System.out.println("result?=?"?+?result);??
??????????????engine.eval("c=a+b");??
??????????????Double?c?=?(Double)engine.get("c");??
??????????????System.out.println("c?=?"?+?c);??
??????????}?catch?(ScriptException?e)?{??
??????????????e.printStackTrace();?????
??????????}????
??????}???
??}??

輸出：
result?=?7.0
c?=?7.0

在Java中調用js文件中的function，傳入調用參數，并獲取返回值

js文件中的merge函數將兩個參數a，b相加，并返回c。

[javascript]?view plain?copy
//?expression.js???
function?merge(a,?b)?{???
?????c?=?a?*?b;???
?????return?c;???
}??

在Java代碼中讀取js文件，并參數兩個參數，然后回去返回值

[java]?view plain?copy
package?com.sinaapp.manjushri;????
?import?java.io.FileReader;????
?import?javax.script.Invocable;??
?import?javax.script.ScriptEngine;??
?import?javax.script.ScriptEngineManager;????
?/**??*?Java調用并執行js文件，傳遞參數，并活動返回值??*???*?@author?manjushri??*/??
?public?class?ScriptEngineTest?{?????
?????public?static?void?main(String[]?args)?throws?Exception?{?????
????????ScriptEngineManager?manager?=?new?ScriptEngineManager();?????
????????ScriptEngine?engine?=?manager.getEngineByName("javascript");??????
?????????String?jsFileName?=?"expression.js";????
?????????//?讀取js文件?????
????????FileReader?reader?=?new?FileReader(jsFileName);?????
????????//?執行指定腳本????
?????????engine.eval(reader);?????
????????if(engine?instanceof?Invocable)?{?????
?????????????Invocable?invoke?=?(Invocable)engine;??????
????????????//?調用merge方法，并傳入兩個參數?????
?????????????//?c?=?merge(2,?3);?????
?????????????Double?c?=?(Double)invoke.invokeFunction("merge",?2,?3);?????
?????????????System.out.println("c?=?"?+?c);?????
????????}?????
????reader.close();???
?}???
}??

輸出結果：
c?=?5.0

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