条件字符串解析器在Java API中？ [英] Condition String Resolver in java API?

问题描述

我想解决以下条件字符串。因为我想在我的项目中支持动态条件。

I would like to resolve the following condtion string. Because I would like to support dynamic condtion in my project.

a != 0 && b > 5

我的预期计划是

public boolean resolve() {
    String condition = "a != 0 && b > 5";
    Map<String, Object> paramMap = new HashMap<String, Object>;
    paramMap.put("a", 2);
    paramMap.put("b", 6);
    boolean result = ConditionResolver.resolve(condition, paramMap);
    if(result) {
        //do something
    }
} 

更新：

我不是要解决数学公式，如下所示

I am not trying to resolve the math equation, like below

((a + b) * y) /x

推荐答案

从java 1.6开始，您可以使用 ScriptEngine 并评估 javascript 对你来说已经足够了和/或如果你不想引入另一个库。

As of java 1.6 you can use the ScriptEngine and evaluate javascript if this is enough for you and/or if you don't want to introduce another library.

ScriptEngine scriptEngine = new ScriptEngineManager().getEngineByName("javascript");
SimpleBindings bindings = new SimpleBindings();

bindings.put("a", 0);
bindings.put("b", 6);

boolean firstEval =  (Boolean) scriptEngine.eval("a != 0 && b > 5", bindings);
System.out.println(firstEval);

bindings.put("a", 2);
bindings.put("b", 6);

boolean secondEval =  (Boolean) scriptEngine.eval("a != 0 && b > 5", bindings);
System.out.println(secondEval);

输出

false
true

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