Skip to main content

使用 Nashorn 进行数据处理

Nashorn 是 Java 的 JS 引擎。它从 Java 8 开始随 Java 发行版一起提供，最终在 Java 15 中被删除。该项目已分拆出来，并提供了适用于 Java 15+ 的兼容独立版本。

¥Nashorn is a JS engine for Java. It shipped with Java distributions starting with Java 8 and was eventually removed in Java 15. The project was spun off and a compatible standalone release is available for Java 15+.

SheetJS 是一个用于从电子表格读取和写入数据的 JavaScript 库。

¥SheetJS is a JavaScript library for reading and writing data from spreadsheets.

"完整示例" 部分包括一个完整的 Java 命令行工具，用于从电子表格读取数据和打印 CSV 行。

¥The "Complete Example" section includes a complete Java command-line tool for reading data from spreadsheets and printing CSV rows.

集成详情​

¥Integration Details

初始化 Nashorn​

¥Initialize Nashorn

Nashorn 不提供 global 变量。必须创建它：

¥Nashorn does not provide a global variable. It must be created:

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Scanner;

/* initialize nashorn engine */
ScriptEngine engine = (new ScriptEngineManager()).getEngineByName("javascript");

/* create global */
engine.eval("var global = (function(){ return this; }).call(null);");

加载 SheetJS 脚本​

¥Load SheetJS Scripts

SheetJS 独立脚本 可以在 Nashorn 上下文中进行解析和评估。

¥The SheetJS Standalone scripts can be parsed and evaluated in a Nashorn context.

可以通过从文件系统读取脚本并在 Nashorn 上下文中进行评估来加载主库：

¥The main library can be loaded by reading the script from the file system and evaluating in the Nashorn context:

engine.eval(new Scanner(
  SheetJS.class.getResourceAsStream("/xlsx.full.min.js")
).useDelimiter("\\Z").next());

要确认库已加载，可以使用 Nashorn print 内置功能打印 XLSX.version：

¥To confirm the library is loaded, XLSX.version can be printed using the Nashorn print built-in:

engine.eval("print('SheetJS Version ' + XLSX.version);");

读取文件​

¥Reading Files

Nashorn 无法正确地将 byte[] 投影到 JS 数组或 Int8Array 中。推荐的解决方法是使用 JS 代码复制 JS 上下文中的数据：

¥Nashorn does not properly project byte[] into a JS array or Int8Array. The recommended workaround is to copy the data in the JS context using the JS code:

function b2a(b) {
  var out = typeof Uint8Array == 'function' ? new Uint8Array(b.length) : new Array(b.length);
  /* `b` is similar to Int8Array (values in the range -128 .. 127 ) */
  for(var i = 0; i < out.length; i++) out[i] = (b[i] + 256) & 0xFF;
  return out;
}

这个函数应该嵌入到 Java 代码中：

¥This function should be embedded in the Java code:

/* read spreadsheet bytes */
engine.put("bytes", Files.readAllBytes(Paths.get(args[0])));

/* convert signed byte array to JS Uint8Array or unsigned byte array */
engine.eval(
  "function b2a(b) {" +
    "var out = typeof Uint8Array == 'function' ? new Uint8Array(b.length) : new Array(b.length);" +
    "for(var i = 0; i < out.length; i++) out[i] = b[i] & 0xFF;" +
    "return out;" +
  "}" +
  "var u8a = b2a(bytes)"
);

/* parse workbook */
engine.eval("var wb = XLSX.read(u8a, {type: 'array'})");

完整示例​

¥Complete Example

测试部署

该演示在以下部署中进行了测试：

¥This demo was tested in the following deployments:

OpenJDKNashorn日期
22.0.115.4 独立版2024-06-24
21.0.315.4 独立版2024-06-24
20.0.215.4 独立版2024-06-24
19.0.215.4 独立版2024-06-24
18.0.215.4 独立版2024-06-24
17.0.1115.4 独立版2024-06-24
16.0.115.4 独立版2024-06-24
15.0.1015.4 独立版2024-06-24
14.0.2内置2024-06-24
13.0.14内置2024-06-24
12.0.2内置2024-06-24
11.0.23内置2024-06-24
10.0.2内置2024-06-24
9内置2024-06-24
1.8.0内置2024-06-24

汇编​

¥Compilation

Nashorn 无需额外依赖即可使用

¥Nashorn is available without additional dependencies

  1. 下载 SheetJS Standalone 脚本、shim 脚本和测试文件。将所有三个文件移动到项目目录：

    ¥Download the SheetJS Standalone script, shim script and test file. Move all three files to the project directory:

curl -LO https://cdn.sheetjs.com/xlsx-0.20.3/package/dist/xlsx.full.min.js
curl -LO https://cdn.sheetjs.com/xlsx-0.20.3/package/dist/shim.min.js
curl -LO https://xlsx.nodejs.cn/pres.xlsx

  1. 下载 SheetJSNashorn.java：

    ¥Download SheetJSNashorn.java:

curl -LO https://xlsx.nodejs.cn/nashorn/SheetJSNashorn.java

  1. 构建示例类：

    ¥Build the sample class:

javac SheetJSNashorn.java

该程序尝试解析第一个参数指定的文件并打印第一个工作表中的 CSV 行。

¥This program tries to parse the file specified by the first argument and prints CSV rows from the first worksheet.

独立测试​

¥Standalone Test

  1. 直接运行命令：

    ¥Run the command directly:

java SheetJSNashorn pres.xlsx

如果成功，将显示第一个工作表中的 CSV 行。

¥If successful, CSV rows from the first worksheet will be displayed.

Java 存档测试​

¥Java Archive Test

  1. 组装 Java 存档：

    ¥Assemble a Java Archive:

jar -cf SheetJSNashorn.jar SheetJSNashorn.class xlsx.full.min.js shim.min.js

  1. 创建新目录并复制存档和测试文件：

    ¥Create new directory and copy the archives and test file:

mkdir -p sheethorn
cp *.jar pres.xlsx sheethorn
cd sheethorn

  1. 使用 Java Archive 运行程序：

    ¥Run the program using the Java Archive:

由于 Java 路径不一致，命令取决于操作系统：

¥Due to Java path inconsistencies, the command depends on the operating system:

java -cp ".:SheetJSNashorn.jar" SheetJSNashorn pres.xlsx

这应该打印与步骤 4 相同的 CSV 行。

¥This should print the same CSV rows from Step 4.