docs.sheetjs.com/docz/docs/03-demos/12-engines/04_nashorn.md

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Nashorn is a JavaScript 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+.

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

Integration Details

Initialize Nashorn

global must be created from a Nashorn engine:

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);");

Load SheetJS Scripts

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());

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

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

Reading Files

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;
}

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] + 256) & 0xFF;" +
    "return out;" +
  "}" +
  "var u8a = b2a(bytes)"
);

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

Complete Example

:::note

This demo was last tested on 2023 March 27 using:

• OpenJDK 19.0.1 + Nashorn 15.4 standalone
• OpenJDK 11.0.18 + Official Nashorn

:::

Nashorn is available without additional dependencies

0. Download Nashorn and its dependencies:

curl -LO "https://search.maven.org/remotecontent?filepath=org/openjdk/nashorn/nashorn-core/15.4/nashorn-core-15.4.jar"
curl -LO "https://search.maven.org/remotecontent?filepath=org/ow2/asm/asm/9.5/asm-9.5.jar"
curl -LO "https://search.maven.org/remotecontent?filepath=org/ow2/asm/asm-tree/9.5/asm-tree-9.5.jar"
curl -LO "https://search.maven.org/remotecontent?filepath=org/ow2/asm/asm-commons/9.5/asm-commons-9.5.jar"
curl -LO "https://search.maven.org/remotecontent?filepath=org/ow2/asm/asm-analysis/9.5/asm-analysis-9.5.jar"
curl -LO "https://search.maven.org/remotecontent?filepath=org/ow2/asm/asm-util/9.5/asm-util-9.5.jar"

1. Download the standalone script, shim script, and the test file:

• xlsx.full.min.js
• shim.min.js
• pres.xlsx

{`\
curl -LO https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js
curl -LO https://cdn.sheetjs.com/xlsx-${current}/package/dist/shim.min.js
curl -LO https://sheetjs.com/pres.xlsx`}

2. Download SheetJSNashorn.java:

curl -LO https://docs.sheetjs.com/nashorn/SheetJSNashorn.java

3. Build the sample class:

javac SheetJSNashorn.java

This program tries to parse the file specified by the first argument

4. Run the command directly:

java SheetJSNashorn pres.xlsx

java -cp .:asm-9.5.jar:asm-tree-9.5.jar:asm-commons-9.5.jar:asm-analysis-9.5.jar:asm-util-9.5.jar:nashorn-core-15.4.jar SheetJSNashorn pres.xlsx

5. Assemble a Java Archive:

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

6. Verify the Java Archive.

Create new directory and copy the archives and test file:

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

Invoke the command in the archive:

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

java -cp .:asm-9.5.jar:asm-tree-9.5.jar:asm-commons-9.5.jar:asm-analysis-9.5.jar:asm-util-9.5.jar:nashorn-core-15.4.jar:SheetJSNashorn.jar SheetJSNashorn pres.xlsx