docs.sheetjs.com/docz/docs/03-demos/42-engines/03_rhino.md

---
title: Java + Rhino
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---

import current from '/version.js';
import CodeBlock from '@theme/CodeBlock';

Rhino is an ES3+ engine in Java.

The [Standalone scripts](/docs/getting-started/installation/standalone) 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:

```java
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:

```java
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:

```java
/* 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:

```swift
/* 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:

```java
  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:

```java
  /* 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 2023-07-26 using Rhino 1.7.14.

:::

0) Ensure Java is installed.  Create a folder for the project, download the
[JAR](https://repo1.maven.org/maven2/org/mozilla/rhino/1.7.14/rhino-1.7.14.jar)
and rename to `rhino.jar`:

```bash
mkdir sheetjs-java
cd sheetjs-java
curl -L -o rhino.jar https://repo1.maven.org/maven2/org/mozilla/rhino/1.7.14/rhino-1.7.14.jar
```

1) Download the standalone script and the test file:

<ul>
<li><a href={`https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js`}>xlsx.full.min.js</a></li>
<li><a href="https://sheetjs.com/pres.xlsx">pres.xlsx</a></li>
</ul>

<CodeBlock language="bash">{`\
curl -LO https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js
curl -LO https://sheetjs.com/pres.xlsx`}
</CodeBlock>

2) Download [`SheetJSRhino.zip`](pathname:///rhino/SheetJSRhino.zip) and unzip

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

3) Save the following code to `SheetJSRhino.java`:

```java title="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:

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

5) Test the program:

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

If successful, a CSV will be printed to console.