javascript脚本怎么运行（js脚本编写教程）

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

1. java 8 中的内置 nashorn javascript 引擎介绍
2. 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

1. new 出 scriptenginemanager 对象
2. 通过 scriptenginemanager 对象中的 getenginebyname 方法获取指定的 javascript 引擎，返回 scriptengine 对象
3. java 8 中的默认的 javascript 引擎包括：[nashorn, nashorn, js, js, javascript, javascript, ecmascript, ecmascript]
4. 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

@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 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

@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();
    }
}

• 输出如下

true
7155
7.0

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

@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 2
print("员工的id 为 1 和 2:\n" + e.employee.(@id == 1 || @id == 2));
// 员工的id 为 1
print("员工的id 为 1: " + e.employee.(@id == 1).name);
print("----------------------------------------");

• 执行如下

@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();
    }
}

• 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

@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();
    }
}

上面的输出结果如下

xml result = true