阿里巴巴开源项目SimpleEL发布0.1版本

Simple EL是一个表达式解析引擎。它将表达式解析分成四个部分：预处理、编译、缓存和执行。这四个步骤任意一部分都可以替换，类似设计模式中的Template Method。 SimpleEL将表达式处理成Java Source，调用Tools.jar的Javac API动态编译，缓存编译后反射得到的实例，使得表达式的解析速度和Java静态编译的速度接近。

这是一个性能极致、扩展性良好的表达式解析引擎。图示 http://code.alibabatech.com/wiki/download/attachments/1966084/simple_el.png?version=2&modificationDate=1302249958000
目前SimpleEL有三种实现，缺省实现，TinyEL，QL，其中TinyEL在下一个版本中将会替换为缺省实现，QL是一种类SQL的表达式语言，它试图创造一种对象查询语言。

Slider : http://code.alibabatech.com/svn/SimpleEL/trunk/doc/SimpleEL.pptx
SVN: http://code.alibabatech.com/svn/simpleel
JIRA: http://code.alibabatech.com/jira/browse/simpleel
WIKI: http://code.alibabatech.com/wiki/display/simpleel/Home

Download: http://code.alibabatech.com/wiki/display/SimpleEL/Download

Maven Repository:

<repository>
	<id>opensesame</id>
	<name>Alibaba OpenSource Repsoitory</name>
	<url>http://code.alibabatech.com/mvn/releases/</url>
	<snapshots>
		<enabled>false</enabled>
	</snapshots>
</repository>

<dependency>
	<groupId>com.alibaba</groupId>
	<artifactId>SimpleEL</artifactId>
	<version>0.1</version>
</dependency>

import com.alibaba.simpleEL.eval.DefaultExpressEvalService;
import com.alibaba.simpleEL.preprocess.DefaultVariantResolver.Type;

DefaultExpressEvalService service = new DefaultExpressEvalService();
service.regsiterVariant(int.class, "a", "b");

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", 3);
ctx.put("b", 4);

Assert.assertEquals(7, service.eval(ctx, "@a + @b"));

DefaultExpressEvalService service = new DefaultExpressEvalService();
service.regsiterVariant(int.class, "a", "b");
service.setAllowMultiStatement(true); //support multi-statement

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", 3);
ctx.put("b", 4);

Assert.assertEquals(1, service.eval(ctx, "if (@a > @b) { return @a - @b; } else {return @b - @a; }"));

TinyEL是SimpleEL中的一种实现，和SimpleEL的缺省实现不同的是，它的预处理不是简单的替换变量，而是经过语法分析之后生成Java Source。变量名称不需要使用@标识。 TinyEL在下一个版本中，可能会升级为SimpleEL的缺省实现。
使用示例：
调用方法

import com.alibaba.simpleEL.dialect.tiny.TinyELEvalService;

TinyELEvalService service = new TinyELEvalService();

service.regsiterVariant(String.class, "name");

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("name", "abc");

Assert.assertEquals(5, service.eval(ctx, "('aa' + name).length()"));

* 调用静态方法

TinyELEvalService service = new TinyELEvalService();

service.regsiterVariant(int.class, "a", "b"); //注册a和b两个变量为int类型

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", 3);
ctx.put("b", 4);

Assert.assertEquals(4, service.eval(ctx, "java.lang.Math.max(a, b)"));

* 构造对象

TinyELEvalService service = new TinyELEvalService();

service.regsiterVariant(long.class, "millis");

long millis = System.currentTimeMillis();
Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("millis", millis);

Assert.assertEquals(new java.util.Date(millis), service.eval(ctx, "new java.util.Date(millis)"));

* 三元表达式

TinyELEvalService service = new TinyELEvalService();

service.regsiterVariant(int.class, "a", "b");

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", 3);
ctx.put("b", 4);

Assert.assertEquals(4, service.eval(ctx, "a > b ? a : b"));
Assert.assertEquals(true, service.eval(ctx, "a instanceof Number"));

* 数组访问

TinyELEvalService service = new TinyELEvalService();

service.regsiterVariant(int.class, "a", "b");
service.regsiterVariant(int[].class, "c");

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", 3);
ctx.put("b", 4);
ctx.put("c", new int[] { 1, 2 });

Assert.assertEquals(4, service.eval(ctx, "Math.max(c[0], c[1]) + 2"));

* 注册函数

TinyELEvalService service = new TinyELEvalService();

service.regsiterVariant(int.class, "a", "b");
service.registerFunction("max", Math.class.getMethod("max", new Class<?>[] { int.class, int.class }));

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", 3);
ctx.put("b", 4);

Assert.assertEquals(7, service.eval(ctx, "a + b"));
Assert.assertEquals(true, service.eval(ctx, "a < b"));
Assert.assertEquals(4, service.eval(ctx, "max(a, b)"));

* 各种运算符

TinyELEvalService service = new TinyELEvalService();

service.regsiterVariant(int.class, "a", "b");

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", 3);
ctx.put("b", 4);

Assert.assertEquals(3, service.eval(ctx, "a++"));
Assert.assertEquals(4, ctx.get("a"));
Assert.assertEquals(5, service.eval(ctx, "++a"));
Assert.assertEquals(5, ctx.get("a"));
Assert.assertEquals(4, service.eval(ctx, "--a"));
Assert.assertEquals(4, ctx.get("a"));
Assert.assertEquals(true, service.eval(ctx, "a > b || b > a || a == b"));
Assert.assertEquals(false, service.eval(ctx, "a > b && b > a && a == b"));
Assert.assertEquals(false, service.eval(ctx, "a != b"));

* 使用if语句 

TinyELEvalService service = new TinyELEvalService();
service.setAllowMultiStatement(true);
service.regsiterVariant(int.class, "a", "b");

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", 3);
ctx.put("b", 4);

Assert.assertEquals(1, service.eval(ctx, "if (a > b) { return a - b; } else {return b - a; }"));

* 声明本地变量

TinyELEvalService service = new TinyELEvalService();
service.setAllowMultiStatement(true);
service.regsiterVariant(int.class, "a", "b");

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", 3);
ctx.put("b", 4);

Assert.assertEquals(70, service.eval(ctx, "int i = 10; return a * i + b * i;"));

* 使用While

TinyELEvalService service = new TinyELEvalService();
service.setAllowMultiStatement(true);
service.regsiterVariant(int.class, "a", "b");

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", 3);
ctx.put("b", 4);

Assert.assertEquals(48, service.eval(ctx, "int i = 0; while (i < 10) { a += i++; } return a;"));

Assert.assertEquals(48, ctx.get("a"));
Assert.assertEquals(4, ctx.get("b"));

* 使用For

TinyELEvalService service = new TinyELEvalService();
service.setAllowMultiStatement(true);
service.regsiterVariant(int.class, "a", "b");

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", 3);
ctx.put("b", 4);

Assert.assertEquals(52, service.eval(ctx, "for (int i = 0; i < 10; ++i) { a += i; } return a + b;"));

Assert.assertEquals(48, ctx.get("a"));
Assert.assertEquals(4, ctx.get("b"));

* 使用ForEach

TinyELEvalService service = new TinyELEvalService();
service.setAllowMultiStatement(true);
service.regsiterVariant(int[].class, "a");

Map<String, Object> ctx = new HashMap<String, Object>();
ctx.put("a", new int[] {1, 2, 3, 4, 5});

Assert.assertEquals(15, service.eval(ctx, "int sum = 0; for (int i : a) { sum += i; } return sum;"));