JEXL表达式计算，支持自定义函数

    1. import java.math.BigDecimal;
    2. import java.util.HashMap;
    3. import java.util.Map;
    5. public class JexlTest {
    7.     public static void main(String[] args) {
    8.         {
    9.             String content = "abs(x-y)";
    10.             Map<String, Number> map = new HashMap<>();
    11.             map.put("x", new BigDecimal("0.9"));
    12.             map.put("y", new BigDecimal("1"));
    14.             Object result = JexlTools.evaluate(content, map);
    15.             System.out.println(content + " = " + result);
    16.         }
    17.         {
    18.             String content = "cos(pi)";
    19.             Map<String, Number> map = new HashMap<>();
    20.             map.put("pi", BigDecimal.valueOf(Math.PI));
    22.             Object result = JexlTools.evaluate(content, map);
    23.             System.out.println(content + " = " + result);
    24.         }
    25.         {
    26.             String content = "sum(x, -y)";
    27.             Map<String, Number> map = new HashMap<>();
    28.             map.put("x", new BigDecimal("0.9"));
    29.             map.put("y", new BigDecimal("1"));
    31.             Object result = JexlTools.evaluate(content, map);
    32.             System.out.println(content + " = " + result);
    33.         }
    34.         {
    35.             String content = "sum(x, y, z)";
    36.             Map<String, Number> map = new HashMap<>();
    37.             map.put("x", new BigDecimal("0.9"));
    38.             map.put("y", new BigDecimal("0.8"));
    39.             map.put("z", new BigDecimal("0.7"));
    41.             Object result = JexlTools.evaluate(content, map);
    42.             System.out.println(content + " = " + result);
    43.         }
    44.     }
    45. }

    JexlTools
    在JexlMath增加方法即可扩展自定义函数

    1. import java.math.BigDecimal;
    2. import java.util.HashMap;
    3. import java.util.Map;
    4. import java.util.Map.Entry;
    5. import org.apache.commons.jexl3.JexlBuilder;
    6. import org.apache.commons.jexl3.JexlContext;
    7. import org.apache.commons.jexl3.JexlEngine;
    8. import org.apache.commons.jexl3.JexlExpression;
    9. import org.apache.commons.jexl3.MapContext;
    11. /**
    12.  * JEXL工具类
    13.  *
    14.  * @author zhaohuihua
    15.  * @version 20210414
    16.  */
    17. public class JexlTools {
    19.     /**
    20.      * 自定义数学函数 (在这里增加方法即可扩展自定义函数)
    21.      *
    22.      * @author zhaohuihua
    23.      * @version 20210414
    24.      */
    25.     public static class JexlMath {
    27.         public BigDecimal sin(BigDecimal x) {
    28.             return BigDecimal.valueOf(Math.sin(x.doubleValue()));
    29.         }
    31.         public BigDecimal cos(BigDecimal x) {
    32.             return BigDecimal.valueOf(Math.cos(x.doubleValue()));
    33.         }
    35.         public BigDecimal abs(BigDecimal x) {
    36.             return x.compareTo(BigDecimal.ZERO) >= 0 ? x : BigDecimal.ZERO.subtract(x);
    37.         }
    39.         public BigDecimal sum(BigDecimal x, BigDecimal y) {
    40.             return x.add(y);
    41.         }
    43.         public BigDecimal sum(BigDecimal x, BigDecimal y, BigDecimal z) {
    44.             return x.add(y).add(z);
    45.         }
    46.     }
    48.     /**
    49.      * 计算表达式
    50.      * 
    51.      * @param expression 表达式
    52.      * @param vars 变量值
    53.      * @return 计算结果
    54.      */
    55.     public static Object evaluate(String expression, Map<String, ?> vars) {
    56.         JexlContext context = new MapContext();
    57.         for (Entry<String, ?> entry : vars.entrySet()) {
    58.             Object value = entry.getValue();
    59.             if (value instanceof Number) {
    60.                 context.set(entry.getKey(), BigDecimal.valueOf(((Number) value).doubleValue()));
    61.             } else {
    62.                 context.set(entry.getKey(), value);
    63.             }
    64.         }
    65.         JexlExpression e = jexl.createExpression(expression);
    66.         return e.evaluate(context);
    67.     }
    69.     private static JexlEngine jexl;
    70.     static {
    71.         Map<String, Object> funcs = new HashMap<String, Object>();
    72.         funcs.put(null, new JexlMath());
    73.         jexl = new JexlBuilder().namespaces(funcs).create();
    74.     }
    75. }

    2.1.1版本的写法，JexlExpression要改为Expression

    1.     private static JexlEngine jexl;
    2.     static {
    3.         Map<String, Object> funcs = new HashMap<String, Object>();
    4.         funcs.put(null, new JexlMath());
    5.         jexl = new JexlEngine();
    6.         jexl.setFunctions(funcs);
    7.     }