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

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Rhino is an ES3+ engine in Java.

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

This demo wraps workbooks and sheets into separate Java classes. The final result is a JAR.

:::caution

Rhino does not support Uint8Array, so certain formats like NUMBERS cannot be parsed or written from Rhino JS code!

:::

Integration Details

:::note

Due to code generation errors, optimization must be turned off:

Context context = Context.enter();
context.setOptimizationLevel(-1);

:::

Binary strings can be passed back and forth.

Initialize Rhino

Rhino does not provide a global variable. It can be created:

Context cx = Context.enter();
Scriptable scope = cx.initStandardObjects();

/* Disable optimization */
cx.setOptimizationLevel(-1);

/* Initialize `global` variable */
// highlight-start
String s = "var global = (function(){ return this; }).call(null);";
cx.evaluateString(scope, s, "<cmd>", 1, null);
// highlight-end

Load SheetJS Scripts

The main library can be loaded by reading the scripts from the Java Archive and evaluating in the Rhino context:

/* pull source from JAR */
String s = new Scanner(
  SheetJS.class.getResourceAsStream("/xlsx.full.min.js")
).useDelimiter("\\Z").next();
/* evaluate */
cx.evaluateString(scope, s, "<cmd>", 1, null);

To confirm the library is loaded, XLSX.version can be inspected:

/* get handle to XLSX */
Object XLSX = scope.get("XLSX", scope);
if(XLSX == Scriptable.NOT_FOUND) throw new Exception("XLSX not found");

/* get the version string */
String version = ((NativeObject)XLSX).get("version", scope).toString();
System.out.println("SheetJS version " + version);

Reading Files

A binary string can be generated from a byte array:

  static String read_file(String file) throws IOException {
    /* read file -> array of bytes */
    byte[] b = Files.readAllBytes(Paths.get(file));

    /* construct binary string */
    StringBuilder sb = new StringBuilder();
    for(int i = 0; i < b.length; ++i) sb.append(Character.toString((char)(b[i] < 0 ? b[i] + 256 : b[i])));
    return sb.toString();
  }

This string can be loaded into the JS engine and processed:

  /* options argument */
  String os = "q = {'type':'binary', 'WTF':1};";
  NativeObject o = (NativeObject)cx.evaluateString(scope, os, "<cmd>", 2, null);

  /* set up function arguments */
  String data = read_file(path_to_file);
  Object args[] = {data, o};

  /* call read -> wb workbook */
  NativeObject nXLSX = (NativeObject)XLSX;
  Function readfunc = (Function)XLSX.get("read", scope);
  NativeObject wb = (NativeObject)readfunc.call(cx, scope, nXLSX, args);

wb will be a reference to the JS workbook object.

Complete Example

:::note

This demo was tested on 2023 February 14 using Rhino 1.7.14.

:::

0. Ensure Java is installed. Create a folder for the project, download the JAR and rename to rhino.jar:

mkdir sheetjs-java
cd sheetjs-java
curl -L -o rhino.jar https://github.com/mozilla/rhino/releases/download/Rhino1_7_14_Release/rhino-1.7.14.jar

1. Download the standalone script and the test file:

• xlsx.full.min.js
• pres.xlsx

curl -LO https://cdn.sheetjs.com/xlsx-latest/package/dist/xlsx.full.min.js
curl -LO https://sheetjs.com/pres.xlsx

2. Download SheetJSRhino.zip and unzip

curl -LO https://docs.sheetjs.com/rhino/SheetJSRhino.zip
unzip SheetJSRhino.zip

3. Save the following code to SheetJSRhino.java:

/* sheetjs (C) 2013-present  SheetJS -- https://sheetjs.com */
/* vim: set ts=2: */
import com.sheetjs.SheetJS;
import com.sheetjs.SheetJSFile;
import com.sheetjs.SheetJSSheet;

public class SheetJSRhino {
  public static void main(String args[]) throws Exception {
    try {
      SheetJS sjs = new SheetJS();

      /* open file */
      SheetJSFile xl = sjs.read_file(args[0]);

      /* get sheetnames */
      String[] sheetnames = xl.get_sheet_names();
      System.err.println(sheetnames[0]);

      /* convert to CSV */
      SheetJSSheet sheet = xl.get_sheet(0);
      String csv = sheet.get_csv();
      System.out.println(csv);
    } catch(Exception e) { throw e; } finally { SheetJS.close(); }
  }
}

4. Assemble SheetJS.jar from the demo code:

javac -cp .:rhino.jar SheetJSRhino.java
jar -cf SheetJS.jar SheetJSRhino.class com/sheetjs/*.class xlsx.full.min.js

5. Test the program:

java -cp .:SheetJS.jar:rhino.jar SheetJSRhino pres.xlsx

If successful, a CSV will be printed to console.