docs.sheetjs.com/docz/docs/03-demos/42-engines/07_nashorn.md

214 lines
5.7 KiB
Markdown
Raw Normal View History

2023-03-28 04:57:47 +00:00
---
title: Java + Nashorn
pagination_prev: demos/bigdata/index
pagination_next: solutions/input
---
2023-04-27 09:12:19 +00:00
import current from '/version.js';
2023-03-28 04:57:47 +00:00
import Tabs from '@theme/Tabs';
import TabItem from '@theme/TabItem';
2023-05-07 13:58:36 +00:00
import CodeBlock from '@theme/CodeBlock';
2023-03-28 04:57:47 +00:00
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](/docs/getting-started/installation/standalone) can be
parsed and evaluated in a Nashorn context.
## Integration Details
_Initialize Nashorn_
`global` must be created from a Nashorn engine:
```java
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:
```java
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:
```java
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:
```js
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:
```java
/* 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);" +
2023-05-22 08:06:09 +00:00
"for(var i = 0; i < out.length; i++) out[i] = b[i] & 0xFF;" +
2023-03-28 04:57:47 +00:00
"return out;" +
"}" +
"var u8a = b2a(bytes)"
);
/* parse workbook */
engine.eval("var wb = XLSX.read(u8a, {type: 'array'})");
```
## Complete Example
:::note
2023-05-22 08:06:09 +00:00
This demo was tested in the following deployments:
2023-03-28 04:57:47 +00:00
2023-05-22 08:06:09 +00:00
| OpenJDK | Nashorn | Date |
|:--------|:----------------|:-----------|
2023-08-28 22:40:53 +00:00
| 21-rc34 | 15.4 standalone | 2023-08-28 |
| 20.0.2 | 15.4 standalone | 2023-08-28 |
| 19.0.2 | 15.4 standalone | 2023-08-28 |
| 17.0.8 | 15.4 standalone | 2023-08-28 |
| 15.0.10 | 15.4 standalone | 2023-08-28 |
| 11.0.20 | Built-in | 2023-08-28 |
| 1.8.0 | Built-in | 2023-08-28 |
2023-03-28 04:57:47 +00:00
:::
<Tabs groupId="java">
<TabItem value="stdlib" label="Java 8 - 14">
Nashorn is available without additional dependencies
</TabItem>
<TabItem value="standalone" label="Java 15+">
0) Download Nashorn and its dependencies:
```bash
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"
```
</TabItem>
</Tabs>
1) Download the standalone script, shim script, and the test file:
<ul>
2023-04-27 09:12:19 +00:00
<li><a href={`https://cdn.sheetjs.com/xlsx-${current}/package/dist/xlsx.full.min.js`}>xlsx.full.min.js</a></li>
<li><a href={`https://cdn.sheetjs.com/xlsx-${current}/package/dist/shim.min.js`}>shim.min.js</a></li>
2023-03-28 04:57:47 +00:00
<li><a href="https://sheetjs.com/pres.xlsx">pres.xlsx</a></li>
</ul>
2023-05-07 13:58:36 +00:00
<CodeBlock language="bash">{`\
2023-04-27 09:12:19 +00:00
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`}
2023-05-07 13:58:36 +00:00
</CodeBlock>
2023-03-28 04:57:47 +00:00
2) Download [`SheetJSNashorn.java`](pathname:///nashorn/SheetJSNashorn.java):
```bash
curl -LO https://docs.sheetjs.com/nashorn/SheetJSNashorn.java
```
3) Build the sample class:
```bash
javac SheetJSNashorn.java
```
This program tries to parse the file specified by the first argument
4) Run the command directly:
<Tabs groupId="java">
<TabItem value="stdlib" label="Java 8 - 14">
```bash
java SheetJSNashorn pres.xlsx
```
</TabItem>
<TabItem value="standalone" label="Java 15+">
```bash
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
```
</TabItem>
</Tabs>
5) Assemble a Java Archive:
```bash
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:
```bash
mkdir -p sheethorn
cp *.jar pres.xlsx sheethorn
cd sheethorn
```
Invoke the command in the archive:
<Tabs groupId="java">
<TabItem value="stdlib" label="Java 8 - 14">
```bash
java -cp .:SheetJSNashorn.jar SheetJSNashorn pres.xlsx
```
</TabItem>
<TabItem value="standalone" label="Java 15+">
```bash
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
```
</TabItem>
</Tabs>