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js腳本編寫教程「javascript腳本怎麼運行」

投稿專員 • • 投稿

1 概述

本文介紹在 Java 環境中執行 JavaScript 腳本的簡單使用，具體包含以下內容

  1. Java 8 中的內置 Nashorn Javascript 引擎介紹
  2. Rhino JavaScript 引擎介紹以及對 XML 的處理介紹

2 Java 8 中的內置 Nashorn Javascript 引擎介紹

Nashorn 是 Java 8 中內置的 JavaScript 引擎，無需加入任何依賴。

Nashorn 基本使用步驟如下

  1. new 出 ScriptEngineManager 對象
  2. 通過 ScriptEngineManager 對象中的 getEngineByName 方法獲取指定的 JavaScript 引擎，返回 ScriptEngine 對象
  3. Java 8 中的默認的 Javascript 引擎包括：[nashorn, Nashorn, js, JS, JavaScript, javascript, ECMAScript, ecmascript]
  4. 通過 ScriptEngine 對象的 eval 方法來執行 JavaScript 腳本。

2.1 通過 PrintWriter 對象獲取腳本中的 print 輸出

Javascript 腳本中沒有函數，沒有返回值，通過 print 輸出內容，這時需要通過 PrintWriter 獲取讀取腳本中的 print 輸出，具體如下

@Test
    public void test_nashorn() {
        try {
            ScriptEngine engine = new ScriptEngineManager().getEngineByName("Nashorn");
            ScriptContext scriptContext = engine.getContext();
            StringWriter stringWriter = new StringWriter();
            PrintWriter printWriter = new PrintWriter(stringWriter);
            scriptContext.setWriter(printWriter);

            String jsString = "var obj=JSON.parse('{\\\"data\\\":\\\"7155\\\",\\\"sign\\\":\\\"success\\\",\\\"message\\\":null}');print(obj.sign==\"success\");";

            stringWriter = new StringWriter();
            printWriter = new PrintWriter(stringWriter);
            scriptContext.setWriter(printWriter);
            engine.eval(jsString);
            System.out.println(String.format("1 result = %s",stringWriter.toString()));

            jsString = "var obj=JSON.parse('{\\\"data\\\":\\\"7157\\\",\\\"sign\\\":\\\"success\\\",\\\"message\\\":null}');print((function getData() {  return obj.data;})())";
            stringWriter = new StringWriter();
            printWriter = new PrintWriter(stringWriter);
            scriptContext.setWriter(printWriter);
            engine.eval(jsString);
            System.out.println(String.format("2 result = %s",stringWriter.toString()));

            jsString = "var obj=JSON.parse('{\\\"data\\\":\\\"7157\\\",\\\"sign\\\":\\\"success\\\",\\\"message\\\":null}');print((function getData() {  return obj.data;})())";
            stringWriter = new StringWriter();
            printWriter = new PrintWriter(stringWriter);
            scriptContext.setWriter(printWriter);
            engine.eval(jsString);
            System.out.println(String.format("3 result = %s",stringWriter.toString()));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

2.2 獲取匿名函數的返回值

Javascript 腳本是一個匿名函數並且有返回值，通過 eval 函數可以直接

@Test
public void test_js_function_return() {
    try {
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("Nashorn");
        String jsFunction = "(function(){var obj=JSON.parse('{\\\"data\\\":\\\"7155\\\",\\\"sign\\\":\\\"success\\\",\\\"message\\\":null}');return obj.sign==\"success\"})();";
        Boolean result = (Boolean) engine.eval(jsFunction);
        System.out.println(result);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

2.3 調用 Javascript 腳本中指定的函數

Javascript 腳本中有變量，有多個函數，具體如下

@Test
public void test_invoke_js_function() {
    try {
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("Nashorn");
        /*
        var obj = JSON.parse('{\"data\":\"7155\",\"sign\":\"success\",\"message\":null}');
        function checkSign() {
            return obj.sign == 'success'
        }
        function getData() {
            return obj.data
        }
        function calculate(a, b) {
            return a + b
        }
         */
        String jsFunction = "var obj=JSON.parse('{\\\"data\\\":\\\"7155\\\",\\\"sign\\\":\\\"success\\\",\\\"message\\\":null}');function checkSign(){return obj.sign=='success'}function getData(){return obj.data}function calculate(a,b){return a+b}";

        engine.eval(jsFunction);
        Invocable invocable = (Invocable) engine;

        Object result = invocable.invokeFunction("checkSign", null);
        System.out.println(result);

        result = invocable.invokeFunction("getData", null);
        System.out.println(result);

        result = invocable.invokeFunction("calculate", 2, 5);
        System.out.println(result);
    } catch (Exception e) {
        e.printStackTrace();
    }
}
  • 輸出如下
true
7155
7.0

2.4 讀取 Javascript 文件並執行

這種情況是讀取 Javascript 文件，並執行，具體如下

  • src/test/resources/test.js
@Test
public void test_invoke_js_file() {
    try {
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("Nashorn");
        engine.eval(new FileReader(TestJSEngine.class.getResource("/test.js").getPath()));
        Invocable invocable = (Invocable) engine;

        Object result = invocable.invokeFunction("checkSign", null);
        System.out.println(result);

        result = invocable.invokeFunction("getData", null);
        System.out.println(result);

        result = invocable.invokeFunction("calculate", 2, 5);
        System.out.println(result);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

文件內容和上面一樣。

3 Rhino JavaScript 引擎介紹

默認的 Nashorn 引擎是無法解析 xml 的，像 DOMParser 這樣的對象是瀏覽器內置的組件。

這裡可以通過 Maven 依賴 Rhino 引擎來處理 xml。

  • Rhino Maven 依賴如下
<dependency>
  <groupId>cat.inspiracio</groupId>
  <artifactId>rhino-js-engine</artifactId>
  <version>1.7.10</version>
</dependency>

使用的步驟和其他 JavaScript 引擎一樣，引擎的名稱為 Rhino.

3.1 Rhino 對 xml 的解析

這裡通過讀取文件的方式來加載和解析 JavaScript 腳本，腳本中是對一段 xml 的解析的過程。

  • src/test/resources/xml.js 文件內容如下
print("----------------------------------------");
var e = new XML('<employees> <employee id="1"><name>Joe</name><age>20</age></employee> <employee id="2"><name>Sue</name><age>30</age></employee>  </employees>');
// 獲取所有的員工
print("獲取所有的員工:\n" + e..name);
// 名字叫 Joe 的員工
print("名字叫 Joe 的員工:\n" + e.employee.(name == "Joe"));
// 員工的id 為 1 和 2
print("員工的id 為 1 和 2:\n" + e.employee.(@id == 1 || @id == 2));
// 員工的id 為 1
print("員工的id 為 1: " + e.employee.(@id == 1).name);
print("----------------------------------------");
  • 執行如下
@Test
public void test_rhino_file_js() {
    try {
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("rhino");

        ScriptContext scriptContext = engine.getContext();

        StringWriter stringWriter = new StringWriter();
        PrintWriter printWriter = new PrintWriter(stringWriter);
        scriptContext.setWriter(printWriter);
        engine.eval(new FileReader(TestJSEngine.class.getResource("/xml.js").getPath()));

        System.out.println(String.format("xml result = %s",stringWriter.toString() ));

    } catch (Exception e) {
        e.printStackTrace();
    }
}
  • 輸出如下
xml result = ----------------------------------------
All the employee names are:
<name>Joe</name>
<name>Sue</name>
The employee named Joe is:
<employee id="1">
  <name>Joe</name>
  <age>20</age>
</employee>
Employees with ids 1 & 2:
<employee id="1">
  <name>Joe</name>
  <age>20</age>
</employee>
<employee id="2">
  <name>Sue</name>
  <age>30</age>
</employee>
Name of the the employee with ID=1: Joe
----------------------------------------

3.2 測試

  • xml 內容如下
<CCardProcessSyncResponse>
    <RetCode>0</RetCode>
    <Message>操作成功！</Message>
    <RefundCycle />
    <EpayRefundCycleMin>1</EpayRefundCycleMin>
    <EpayRefundCycleMax>7</EpayRefundCycleMax>
    <EpayRefundCycleUnitF />
</CCardProcessSyncResponse>
  • 具體測試如下
@Test
public void test_rhino() {
    try {
        ScriptEngine engine = new ScriptEngineManager().getEngineByName("rhino");

        String jsString = jsString = "var obj=new XML('<CCardProcessSyncResponse>    <RetCode>0</RetCode>    <Message>操作成功！</Message>    <RefundCycle />    <EpayRefundCycleMin>1</EpayRefundCycleMin>    <EpayRefundCycleMax>7</EpayRefundCycleMax>    <EpayRefundCycleUnitF />  </CCardProcessSyncResponse>');print(obj.Message == '操作成功！');";
        ScriptContext scriptContext = engine.getContext();

        StringWriter stringWriter = new StringWriter();
        PrintWriter printWriter = new PrintWriter(stringWriter);
        scriptContext.setWriter(printWriter);
        engine.eval(jsString);

        System.out.println(String.format("xml result = %s",stringWriter.toString() ));

    } catch (Exception e) {
        e.printStackTrace();
    }
}

上面的輸出結果如下

xml result = true

原創文章，作者：投稿專員，如若轉載，請註明出處：https://www.506064.com/zh-hant/n/269567.html

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