自定义表达式解析器

解析器：

import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.util.ArrayList;
import java.util.List;
import java.util.regex.Pattern;

import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;

import com.tf.arithmetic.bean.Exterior;

/**
 * 自定义计算表达式解析器和计算器
 * 表达式的写法：@{占位变量}
 * @author yzl
 *
 */
public class ExpressionResolver {
    private ExpressionResolver(){}
    private static ExpressionResolver resolver = null;
    public static ExpressionResolver getInstance(){
        if(null==resolver){
            resolver = new ExpressionResolver();
        }
        return resolver;
    }

    /**
     * 计算表达式的结果
     * @param expression  解析包含@{}的表达式
     * @param bean
     * @param precision
     * @return
     * @throws ScriptException
     * @throws NoSuchMethodException
     * @throws SecurityException
     * @throws IllegalAccessException
     * @throws IllegalArgumentException
     * @throws InvocationTargetException
     */
    public double getExecuteResult(String expression, Object bean, int precision) throws ScriptException, NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
        expression = this.parse(expression, bean);
        ScriptEngine se = new ScriptEngineManager().getEngineByName("JavaScript");
        double result = (Double) se.eval(expression);
        return MathUtils.multiply(result, 1d, precision);
    }

    /**
     * 解析自定义的@{}表达式
     * (@{ys}*[email protected]{csd}*[email protected]{jg}*[email protected]{sf}*[email protected]{yf}*[email protected]{sd}*0.08)*10
     * @param expression
     * @param bean
     * @return
     * @throws SecurityException
     * @throws NoSuchMethodException
     * @throws InvocationTargetException
     * @throws IllegalArgumentException
     * @throws IllegalAccessException
     */
    private String parse(String expression, Object bean) throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException{
        //保存表达式中的所有变量
        List<String> variableList = new ArrayList<String>();

        String reg = "@\\{";
        String reg2 = "\\}";
        Pattern pattern = Pattern.compile(reg);
        Pattern pattern2 = Pattern.compile(reg2);
        String[] arr = pattern.split(expression);
        for(int i=0; i<arr.length; i++){
            if(!"(".equals(arr[i]) && !")".equals(arr[i])){
                variableList.add(pattern2.split(arr[i])[0]);
            }
        }

        String fieldName = null;
        String methodName = null;
        Object result = null;

        //用值替换表达式中的变量
        if(variableList.size()>0){
            Field[] field = bean.getClass().getDeclaredFields();
            for(int i=0; i<field.length; i++){
                fieldName = field[i].getName();
                methodName = "get"+fieldName.substring(0,1).toUpperCase()+fieldName.substring(1);
                result = bean.getClass().getMethod(methodName, null).invoke(bean);
                expression = expression.replace("@{"+fieldName+"}", result.toString());
            }
        }

        return expression;
    }

    public static void main(String[] args) throws Exception {
        String input = "(@{ys}*[email protected]{csd}*[email protected]{jg}*[email protected]{sf}*[email protected]{yf}*[email protected]{sd}*0.08)*10";
        String reg = "@\\{";
        String reg2 = "\\}";
        Pattern pattern = Pattern.compile(reg);
        Pattern pattern2 = Pattern.compile(reg2);
        String[] arr = pattern.split(input);
        for(int i=0; i<arr.length; i++){
            if(!"(".equals(arr[i]) && !")".equals(arr[i])){
                System.out.println("得到变量:"+pattern2.split(arr[i])[0]);
            }
        }

        Exterior bean = new Exterior(8,8,8,8,8,8);
        double val = ExpressionResolver.getInstance().getExecuteResult(input, bean, 2);
        System.out.println(val);
    }
}

需要的实体bean(例子)：

/**
 * 某模型的pojo对象
 * @author yzl
 *
 */
public class Exterior {
    private int ys;
    private int csd;
    private int jg;
    private int sf;
    private int yf;
    private int sd;

    public int getYs() {
        return ys;
    }
    public void setYs(int ys) {
        this.ys = ys;
    }
    public int getCsd() {
        return csd;
    }
    public void setCsd(int csd) {
        this.csd = csd;
    }
    public int getJg() {
        return jg;
    }
    public void setJg(int jg) {
        this.jg = jg;
    }
    public int getSf() {
        return sf;
    }
    public void setSf(int sf) {
        this.sf = sf;
    }
    public int getYf() {
        return yf;
    }
    public void setYf(int yf) {
        this.yf = yf;
    }
    public int getSd() {
        return sd;
    }
    public void setSd(int sd) {
        this.sd = sd;
    }

    public Exterior(int ys, int csd, int jg, int sf, int yf, int sd) {
        super();
        this.ys = ys;
        this.csd = csd;
        this.jg = jg;
        this.sf = sf;
        this.yf = yf;
        this.sd = sd;
    }

    public Exterior() {
        super();
    }
}