JSR 223 lets you use the power and flexibility of scripting languages like Ruby, Groovy, and Python on the Java Platform.
Camel supports a number of scripting languages which can be used to create an Expression or Predicate via the standard JSR 223 which is a standard part of Java 6.
Dependencies
使用脚本语言需要添加依赖包 org.apache.camel:camel-script
<dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-script</artifactId>
</dependency>
Scripting
在 Camel 中使用脚本语言有两种情况，作为表达式或者作为脚本文件。两种脚本都可以使用为 ScriptContext 预设置的全局属性，下列
| Attribute | Type | Value |
|---|---|---|
| camelContext | org.apache.camel.CamelContext | The Camel Context. |
| context | org.apache.camel.CamelContext | The Camel Context (cannot be used in groovy). |
| exchange | org.apache.camel.Exchange | The current Exchange. |
| properties | org.apache.camel.builder.script.PropertiesFunction | Camel 2.9: Function with a resolve method to make it easier to use Camels Properties component from scripts. See further below for example. |
| request | org.apache.camel.Message | The IN message. |
| response | org.apache.camel.Message | Deprecated: The OUT message. The OUT message is null by default. Use the IN message instead. |
更详细的脚本引擎创建过程和属性设置参考代码类
org.apache.camel.builder.script.ScriptBuilder
Expression
表达式是指在 Route 里用脚本语言书写一种结果为 true 或 false 的语句，来作为某种判断的依据，例如：
from("direct:books")
.choice()
.when().javaScript("request.headers.get('user') == 'admin'")
.bean("bookRepository", "getByRole(\"admin\")")
.otherwise()
.bean("bookRepository", "getByRole(\"visitor\")");
Script File
如果想要使用脚本文件，可以使用这样的URI
language://languageName:resource:scheme:[location][?options]
.otherwise()
.to("language://javascript:resource:classpath:test-javascript.js?transform=false");
详细请参考 Camel Language component
Load Another Script File
有些情况下需要在主JavaScript文件中加载另外的JavaScript文件，这就可以使用 Nashorn extensions 中的 load function:
load("classpath:WechatClient.js");
importClass
在JavaScript脚本文件中引入Java类可以使用 Nashorn extensions 中的 Java.type function，当然也可以直接使用Java类全名如java.lang.System.out.println():
var System = Java.type("java.lang.System");
System.out.println(request.getHeaders().toString());
如果使用了旧版的Rhino引擎中的importClass可以先加载 nashorn:mozilla_compat.js，然后才能使用
load("nashorn:mozilla_compat.js");
importClass(java.lang.System);
System.out.println(request.getHeaders().toString());
如果并不确定的话可以捕获异常或者先进行判断
// if you want the script run both on rhino and nashorn
try {
load("nashorn:mozilla_compat.js");
} catch (e) {}
// Or you can check for importClass function and then load if missing ...
if (typeof importClass != "function") {
load("nashorn:mozilla_compat.js");
}
jdk8 replaces Rhino based jsr-223 script engine with nashorn based jsr-223 script engine. You can check out the Rhino Migration Guide
Groovy Script
Groovy Json
http://groovy-lang.org/json.html
Groovy XML
http://groovy-lang.org/processing-xml.html
本文完整代码 Github
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