安卓(Android)或者Java使用rhino实现任意字符串表达式计算
安卓(Android)或者Java使用rhino实现任意字符串表达式计算
本文连接：https://www.cnblogs.com/muphy/p/15253488.html
Java使用rhino
引入依赖包
<!-- https://mvnrepository.com/artifact/org.mozilla/rhino --><dependency>
<groupId>org.mozilla</groupId>
<artifactId>rhino</artifactId>
<version>1.7.13</version>
</dependency>
初始rhino的Context
Context.enter();
安卓系统使用rhino不太一样，安卓使用参考：https://github.com/F43nd1r/rhino-android
引入依赖包
implementation 'com.faendir.rhino:rhino-android:1.6.0'//implementation group: 'org.mozilla', name: 'rhino', version: '1.7.13'
初始化rhino的Context
//这里参数context使用Android的Contextnew RhinoAndroidHelper(context).enterContext()
AndroidContextHolder.java
import android.content.Context;public class AndroidContextHolder {
private static Context context;
public static Context getContext() {
return context;
}
public static void setContext(Context context) {
AndroidContextHolder.context = context;
}
}
CalculateUtils.java
//package com.moefon.power.spring.util;import org.mozilla.javascript.Context;
import org.mozilla.javascript.Function;
import org.mozilla.javascript.Scriptable;
import org.mozilla.javascript.Undefined;
import java.util.Stack;
/**
* 将字符串转计算公式
* Object r1 = evaluate("function f(){var x = 5; y = 455; var m = {'x':x,'y':y}; return x}; var i = f();"); // Undefined
* Object r2 = evaluate("function f(){var x = 5; y = 455; var m = {'x':x,'y':y}; return x}; var i = f(); i;"); // Integer:5
* Object r3 = evaluate("var f = function(){var x = 5; var m = {'x':x,'y':55}; return m}; var i = f();", "i"); // NativeObject:{'x':x,'y':y}
* Object r4 = evaluate("var f = function(v){var x = 5; var m = {'x':x,'y':v}; return m;};", "f", 1); // NativeObject:{'x':x,'y':y}
* Object r5 = evaluate("var f = function(v){var x = 5; var m = {'x':x,'y':v}; return x + v;};", "f", 1); // Double:5
*
* AndroidContextHolder.getContext() 表示安卓启动的时候记得设置activity或者application
*
* @author: 若非
* @date: 2021/9/9 20:43
*/
public class CalculateUtils {
/**
* 将字符串转计算公式 {@code evaluate(7+ +55 + +5 * (2-5)) }
*
* @param js
* @return: 计算结果
* @author: 若非
* @date: 2021/9/9 20:43
*/
public static <T> T evaluate(String js) {
Context ctx = new RhinoAndroidHelper(AndroidContextHolder.getContext).enterContext();
Scriptable scope = ctx.initStandardObjects(); //初始化本地对象
T result = null;
try {
Object o = ctx.evaluateString(scope, js, "", 1, null);
if (o != Scriptable.NOT_FOUND && !(o instanceof Undefined)) {
result = (T) o;//执行
}
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
/**
* 执行JS代码
*
* @param js
* @param resultName scope中获取返回参数名称
* @return: js对象 计算结果
* @author: 若非
* @date: 2021/9/9 20:43
*/
public static <T> T evaluate(String js, String resultName) {
Context ctx = new RhinoAndroidHelper(AndroidContextHolder.getContext()).enterContext();
Scriptable scope = ctx.initStandardObjects(); //初始化本地对象
T result = null;
try {
ctx.evaluateString(scope, js, "", 1, null);//执行
} catch (Exception e) {
e.printStackTrace();
}
Object o = scope.get(resultName, scope);
if (o != Scriptable.NOT_FOUND && !(o instanceof Undefined)) {
result = (T) o;//执行
}
return result;
}
/**
* 执行JS代码
*
* @param js js代码
* @param functionName js方法名称
* @param functionParams js方法参数
* @return js对象
* @author: 若非
* @date: 2021/9/9 20:43
*/
public static <T> T evaluate(String js, String functionName, Object... functionParams) {
Context ctx = new RhinoAndroidHelper(AndroidContextHolder.getContext()).enterContext();
ctx.setOptimizationLevel(-1);
T result = null;
try {
Scriptable scope = ctx.initStandardObjects();
ctx.evaluateString(scope, js, null, 1, null);
Function function = (Function) scope.get(functionName, scope);
Object o = function.call(ctx, scope, scope, functionParams);
if (o != Scriptable.NOT_FOUND && !(o instanceof Undefined)) {
result = (T) o;//执行
}
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
/**
* 加减乘除计算 使用包装类方便取值
*
* @param expression
* @return
* @author: 若非
* @date: 2021/9/9 20:43
* @see this#evaluate
* @deprecated {@code this.evaluate}
*/
@Remind(deprecated = true, notice = "请使用evaluate方法来进行表达式计算，这里只支持+-*/")
public static Double calculationResult(String expression) {
char[] chars = expression.toCharArray();
Stack<String> stack = new Stack<>();
StringBuilder stringBuilder = new StringBuilder();
for (int i = 0; i < chars.length; i++) {
switch (chars[i]) {
case '+':
case '-':
stack.push(stringBuilder.toString());
stack.push(String.valueOf(calculationResult(stack)));
stack.push(chars[i] + "");
stringBuilder = new StringBuilder();
break;
case '*':
case '/':
stack.push(stringBuilder.toString());
stack.push(chars[i] + "");
stringBuilder = new StringBuilder();
break;
default:
stringBuilder.append(chars[i]);
}
}
stack.push(stringBuilder.toString());
Double v = calculationResult(stack);
return v;
}
/**
* 加减乘除计算 使用包装类方便取值
*
* @param stack
* @return 执行结果
* @author: 若非
* @date: 2021/9/9 20:43
* @see this#evaluate
* @deprecated {@code this.evaluate}
*/
private static Double calculationResult(Stack<String> stack) {
double res = Double.parseDouble(stack.pop());
while (!stack.empty()) {
String opt = stack.pop();
double second = Double.parseDouble(stack.pop());
res = calculation(res, second, opt.charAt(0));
}
return res;
}
/**
* 加减乘除计算 使用包装类方便取值
*
* @param res
* @param x
* @param opt
* @return 执行结果
* @author: 若非
* @date: 2021/9/9 20:43
* @see this#evaluate
* @deprecated {@code this.evaluate}
*/
private static Double calculation(double res, double x, char opt) {
switch (opt) {
case '+':
return res + x;
case '-':
return x - res;
case '*':
return res * x;
case '/':
if (x < 0.0000000001f) {
return Double.MAX_VALUE;
}
return x / res;
default:
return res;
}
}
}
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