1 概述

本文介绍在 Java 环境中执行 JavaScript 脚本的简单使用，具体包含以下内容

Java 8 中的内置 Nashorn Javascript 引擎介绍

Rhino JavaScript 引擎介绍以及对 XML 的处理介绍

2 Java 8 中的内置 Nashorn Javascript 引擎介绍

Nashorn 是 Java 8 中内置的 JavaScript 引擎，无需加入任何依赖。

Nashorn 基本使用步骤如下

new 出 ScriptEngineManager 对象

通过 ScriptEngineManager 对象中的 getEngineByName 方法获取指定的 JavaScript 引擎，返回 ScriptEngine 对象

Java 8 中的默认的 Javascript 引擎包括：[nashorn, Nashorn, js, JS, JavaScript, javascript, ECMAScript, ecmascript]

通过 ScriptEngine 对象的 eval 方法来执行 JavaScript 脚本。

2.1 通过 PrintWriter 对象获取脚本中的 print 输出

Javascript 脚本中没有函数，没有返回值，通过 print 输出内容，这时需要通过 PrintWriter 获取读取脚本中的 print 输出，具体如下

@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 获取匿名函数的返回值

Javascript 脚本是一个匿名函数并且有返回值，通过 eval 函数可以直接

@Testpublic 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 调用 Javascript 脚本中指定的函数

Javascript 脚本中有变量，有多个函数，具体如下

@Testpublic 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(); }}

• 输出如下

true71557.0

2.4 读取 Javascript 文件并执行

这种情况是读取 Javascript 文件，并执行，具体如下

• src/test/resources/test.js

@Testpublic 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(); }}

文件内容和上面一样。

3 Rhino JavaScript 引擎介绍

默认的 Nashorn 引擎是无法解析 xml 的，像 DOMParser 这样的对象是浏览器内置的组件。

这里可以通过 Maven 依赖 Rhino 引擎来处理 xml。

• Rhino Maven 依赖如下

<dependency> <groupId>cat.inspiracio</groupId> <artifactId>rhino-js-engine</artifactId> <version>1.7.10</version></dependency>

使用的步骤和其他 JavaScript 引擎一样，引擎的名称为 Rhino.

3.1 Rhino 对 xml 的解析

这里通过读取文件的方式来加载和解析 JavaScript 脚本，脚本中是对一段 xml 的解析的过程。

• src/test/resources/xml.js 文件内容如下

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>');// 获取所有的员工print("获取所有的员工:n" + e..name);// 名字叫 Joe 的员工print("名字叫 Joe 的员工:n" + e.employee.(name == "Joe"));// 员工的id 为 1 和 2print("员工的id 为 1 和 2:n" + e.employee.(@id == 1 || @id == 2));// 员工的id 为 1print("员工的id 为 1: " + e.employee.(@id == 1).name);print("----------------------------------------");

• 执行如下

@Testpublic 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(); }}

• 输出如下

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 测试

• xml 内容如下

<CCardProcessSyncResponse> <RetCode>0</RetCode> <Message>操作成功！</Message> <RefundCycle /> <EpayRefundCycleMin>1</EpayRefundCycleMin> <EpayRefundCycleMax>7</EpayRefundCycleMax> <EpayRefundCycleUnitF /></CCardProcessSyncResponse>

• 具体测试如下

@Testpublic 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(); }}

上面的输出结果如下

xml result = true