Taming Data with Rhino

Rhino is an ES3+ engine in Java.

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

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

Rhino does not support Uint8Array, so NUMBERS files cannot be read or written.

Tested Deployments

This demo was tested in the following deployments:

OpenJDK	Rhino	Date
22	1.7.14	2024-04-04
21.0.3	1.7.15	2024-05-24
20.0.2	1.7.15	2024-05-25
19.0.2	1.7.15	2024-05-25
18.0.2	1.7.15	2024-05-25
17.0.11	1.7.15	2024-05-25
16.0.1	1.7.15	2024-05-25
15.0.10	1.7.15	2024-05-25
14.0.2	1.7.15	2024-05-25
13.0.14	1.7.15	2024-05-25
12.0.2	1.7.15	2024-05-25
11.0.22	1.7.15	2024-05-25
10.0.2	1.7.15	2024-05-25
9	1.7.15	2024-05-25
1.8.0	1.7.14	2024-04-25

Integration Details

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

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

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

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 */
String s = "var global = (function(){ return this; }).call(null);";
cx.evaluateString(scope, s, "<cmd>", 1, null);

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

0. Ensure Java is installed.

1. Create a folder for the project:

mkdir sheetjs-java
cd sheetjs-java

2. Download the Rhino JAR and rename to rhino.jar:

curl -L -o rhino.jar https://repo1.maven.org/maven2/org/mozilla/rhino/1.7.15/rhino-1.7.15.jar

3. Download the SheetJS Standalone script and the test file. Save both files in the project directory:

• xlsx.full.min.js
• pres.xlsx

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

4. Download SheetJSRhino.zip and unzip

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

5. Save the following code to SheetJSRhino.java:

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(); }
  }
}

6. Assemble SheetJS.jar from the demo code:

Linux/MacOS

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

Windows

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

7. Test the program:

Linux/MacOS

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

Windows

java -cp ".;SheetJS.jar;rhino.jar" SheetJSRhino pres.xlsx

If successful, a CSV will be printed to console.