NashornScriptEngine CompileScript Cache

scratch_16.java

import cn.hutool.core.convert.Convert;
import jdk.nashorn.api.scripting.NashornScriptEngine;
import lombok.NonNull;

import javax.script.Bindings;
import javax.script.Compilable;
import javax.script.CompiledScript;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import javax.script.SimpleBindings;
import java.math.BigDecimal;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;
import java.util.function.Function;

/**
 * 这是一个 {@link NashornScriptEngine } 执行脚本缓存 <p>
 * 说明：使用 {@link NashornScriptEngine } 执行 <code>JavaScript</code> 脚本时，每次会 compile 脚本，影响性能的同时还存在CAS问题<br>
 * 因此，缓存编译后的Script对象非常有必要，尤其在高并发系统中使用 {@link NashornScriptEngine}
 *
 * @author XS <[email protected]>
 * @date 2023/05/10
 */
class Scratch {
    public static void main(String[] args) throws ScriptException {
        String scriptText = "Math.floor(100+13*Math.pow(1.014,data.level)*(data.level-1))";
        Bindings bindings = new SimpleBindings();
        Map<Object, Object> data = new HashMap<>();
        data.put("level", 10);
        bindings.put("data", data);
        BigDecimal eval = ScriptHolder.eval(1000L, scriptText, bindings, Convert::toBigDecimal);
        System.out.println(eval);

        bindings = new SimpleBindings();
        data = new HashMap<>();
        data.put("level", 10);
        bindings.put("data", data);
        eval = ScriptHolder.eval(1000L, scriptText, bindings, Convert::toBigDecimal);
        System.out.println(eval);
    }
}

class ScriptHolder {
    /** 脚本引擎 */
    private static final Compilable SCRIPT_ENGINE = (Compilable) new ScriptEngineManager().getEngineByName("nashorn");
    /** 编译脚本缓存 */
    private static final Map<Long, CompiledScript> COMPILED_SCRIPT_CACHE = new HashMap<>();

    /**
     * 执行脚本 <p>
     *
     * 如果存在脚本编译缓存，直接拿编译后的Script实例来执行脚本，否则缓存
     * @param scriptId 脚本id，缓存Key
     * @param scriptText 脚本文本
     * @param bindings 绑定参数对象，无参数传一个 bindings 实例
     * @param converter 类型转换
     * @return {@link Object}
     * @throws ScriptException 脚本异常
     */
    public static <T> T eval(
            @NonNull Long scriptId,
            @NonNull String scriptText,
            @NonNull Bindings bindings,
            @NonNull Function<Object, T> converter)
            throws ScriptException {
        CompiledScript compiledScript = COMPILED_SCRIPT_CACHE.get(scriptId);
        return converter.apply(Optional.ofNullable(compiledScript)
                .orElseGet(() -> {
                    CompiledScript script;
                    try {
                        script = SCRIPT_ENGINE.compile(scriptText);
                    } catch (ScriptException e) {
                        throw new RuntimeException(e);
                    }
                    COMPILED_SCRIPT_CACHE.put(scriptId, script);
                    return script;
                })
                .eval(bindings));
    }
}