package com.alibaba.tamper.process.script.jexl;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import org.apache.commons.jexl2.Expression;
import org.apache.commons.jexl2.Interpreter;
import org.apache.commons.jexl2.JexlContext;
import org.apache.commons.jexl2.JexlEngine;
import org.apache.commons.jexl2.MapContext;
import org.apache.commons.jexl2.parser.JexlNode;
import com.alibaba.tamper.process.script.ScriptContext;
import com.alibaba.tamper.process.script.ScriptExecutor;
import com.alibaba.tamper.process.script.lifecyle.DisposableScript;
import com.alibaba.tamper.process.script.lifecyle.InitializingScript;
/**
* Jexl的script实现
*
* @author jianghang 2011-5-25 下午08:08:45
*/
public class JexlScriptExecutor implements ScriptExecutor {
private static final int DEFAULT_CACHE_SIZE = 1000;
private ScriptJexlEngine engine;
private Map<String, Object> functions;
private int cacheSize = DEFAULT_CACHE_SIZE;
public JexlScriptExecutor(){
initialize();
}
/**
* 初始化function
*/
public void initialize() {
if (cacheSize <= 0) {// 不考虑cacheSize为0的情况，强制使用LRU cache机制
cacheSize = DEFAULT_CACHE_SIZE;
}
functions = new HashMap<String, Object>();
engine = new ScriptJexlEngine();
engine.setCache(cacheSize);
engine.setSilent(true);
engine.setFunctions(functions); // 注册functions
}
public ScriptContext genScriptContext(Map<String, Object> context) {
return new JexlScriptContext(context);
}
public Object evaluate(Map<String, Object> context, String script) {
return evaluate(genScriptContext(context), script);
}
/**
* <pre>
* 1. 接受JexlScriptContext上下文
* 2. script针对对应name下的script脚本
* </pre>
*/
public Object evaluate(ScriptContext context, String script) {
Expression expr = engine.createExpression(script);
return expr.evaluate((JexlContext) context);
}
// ============================ setter / getter ============================
public void setCacheSize(int cacheSize) {
this.cacheSize = cacheSize;
}
public void addFunction(String name, Object obj) {
this.functions.put(name, obj);
}
public void disposeFunctions() {
engine.disposeUsedFunctions();
}
}
/**
* 定义为Jexl context
*
* @author jianghang 2011-5-25 下午07:57:59
*/
class JexlScriptContext extends MapContext implements ScriptContext {
public JexlScriptContext(Map map){
super(map);
}
}
/**
* 扩展jexl的实现，提供{@linkplain InitializingScript},{@linkplain DisposableScript}的管理
*/
class ScriptJexlEngine extends JexlEngine {
// 记录script执行过程中使用过的function
private ThreadLocal<Set<Object>> usedFunctions = null;
public ScriptJexlEngine(){
super(null, null, null, null);
usedFunctions = new ThreadLocal<Set<Object>>() {
protected Set<Object> initialValue() {
return new HashSet<Object>(); // 线程安全，不全同步
}
};
}
protected Interpreter createInterpreter(JexlContext context) {
if (context == null) {
context = EMPTY_CONTEXT;
}
return new ScriptInterpreter(this, context);
}
class ScriptInterpreter extends Interpreter {
public ScriptInterpreter(JexlEngine jexl, JexlContext aContext){
super(jexl, aContext);
}
protected Object resolveNamespace(String prefix, JexlNode node) {
Object result = super.resolveNamespace(prefix, node);
if (result != null) {
boolean contains = usedFunctions.get().add(result);// 添加到使用记录中
if (contains && InitializingScript.class.isAssignableFrom(result.getClass())) {// 第一次添加
((InitializingScript) result).initial();// 回调
}
}
return result;
}
}
public void disposeUsedFunctions() {
try {
Set<Object> functions = usedFunctions.get();
for (Object function : functions) {
if (function != null && DisposableScript.class.isAssignableFrom(function.getClass())) {
((DisposableScript) function).dispose();// 回调
}
}
} finally {
usedFunctions.set(new HashSet<Object>());// 清空
}
}
}