关于java:从0到1编写一个脚本引擎

应用 Java 实现 JS 脚本引擎

我的项目地址

https://github.com/GitHub-Laz…

• 反对解析 js 脚本生成语法树
• 反对运行残缺 js 脚本
• 反对平安模式运行单行表达式
• 反对设置超时工夫

打包后命令行运行

git clone https://github.com/GitHub-Laziji/js-engine.git
cd js-engine
mvn package
cd target

java -jar ./js-engine-1.0-SNAPSHOT-jar-with-dependencies.jar ./test.js

或者装置后间接引入依赖

git clone https://github.com/GitHub-Laziji/js-engine.git
cd js-engine
mvn install

<dependency>
    <groupId>org.laziji.commons</groupId>
    <artifactId>js-engine</artifactId>
    <version>1.0-SNAPSHOT</version>
</dependency>

1. 生成语法树 并输入格式化代码

示例代码

class Test{public static void main(String[] args){Top.init();
        DocNode doc = Top.compile("let      a=1+2,b=3,c=\"string\",d=a*(b+c/2),func=function(){};");
        System.out.println(doc);
    }
}

输入

let a = 1 + 2, b = 3, c = "string", d = a * (b + c / 2), func = function () {}

2. 运行残缺脚本

以下示例为运行快排算法（运行环境线程隔离）

示例代码

class Test{
    /**
     * function sort(arr, i, j) {*   if (i >= j) {
     *     return;
     *   }
     *   let p = i, q = j;
     *   let temp = arr[p];
     *   while (p < q) {*     while (p < q && arr[q] >= temp) {
     *       q-=1;
     *     }
     *     arr[p] = arr[q];
     *     while (p < q && arr[p] <= temp) {
     *       p+=1;
     *     }
     *     arr[q] = arr[p];
     *   }
     *   arr[q] = temp;
     *   sort(arr, i, q - 1);
     *   sort(arr, q + 1, j);
     * }
     *
     * let arr = [234, 57, 12, 123, 346, 1234, 2];
     *
     * sort(arr, 0, arr.length - 1);
     */
    public static void main(String[] args){Top.init();
        Top.eval("function sort(arr, i, j) {\n" +
                "if (i >= j) {\n" +
                "return;\n" +
                "}\n" +
                "let p = i, q = j;\n" +
                "let temp = arr[p];\n" +
                "while (p < q) {\n" +
                "while (p < q && arr[q] >= temp) {\n" +
                "q-=1;\n" +
                "}\n" +
                "arr[p] = arr[q];\n" +
                "while (p < q && arr[p] <= temp) {\n" +
                "p+=1;\n" +
                "}\n" +
                "arr[q] = arr[p];\n" +
                "}\n" +
                "arr[q] = temp;\n" +
                "sort(arr, i, q - 1);\n" +
                "sort(arr, q + 1, j);\n" +
                "}\n" +
                "\n" +
                "let arr = [234, 57, 12, 123, 346, 1234, 2];\n" +
                "\n" +
                "sort(arr, 0, arr.length - 1);");
        Top.loop();
        System.out.println(Top.getThreadLocalTop().getMainContexts().getContexts().peek().toSimpleString());
    }
}

输入

arr: [2, 12, 57, 123, 234, 346, 1234]
sort: [object Object]

3. 运行单行表达式

该模式下只反对单行表达式 并且无奈应用 for、while、function、lambda、import 关键字

示例代码

class Test{public static void main(String[] args){Top.init();
        System.out.println(Top.exprEval("'hello'+(1*2*3*4)"));
    }
}

输入

hello 24

4. 设置超时工夫

通过 Top.getThreadLocalTop().setOvertime(100L); 设置超时工夫，单位毫秒

示例代码

class Test{public static void main(String[] args){Top.init();
        Top.getThreadLocalTop().setOvertime(100L);
        Top.addInternalModules("sys", new SystemModuleValue());
        Top.eval("import { print} from \"sys\";\n" +
                "\n" +
                "let i=1;\n" +
                "while(true){\n" +
                "print(i++);\n" +
                "}");
        Top.loop();}
}

输入

1
2
3
...

org.laziji.commons.js.exception.RunException: Run timeout.
...