表达式计算的浮点数精度问题

结论

注(1)：ognl 版本问题
计算 “a<=-0.1”，当 a = new BigDecimal(“-0.1”) 时，本应返回true，但是 ognl <= 2.7.1 版本返回false

测试代码

import java.io.Serializable;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import org.apache.commons.jexl3.JexlContext;
import org.apache.commons.jexl3.JexlEngine;
import org.apache.commons.jexl3.JexlExpression;
import org.apache.commons.jexl3.MapContext;
import org.apache.commons.jexl3.internal.Engine;
import org.cheffo.jeplite.JEP;
import org.codehaus.janino.ExpressionEvaluator;
import org.mvel2.MVEL;
import com.gitee.qdbp.tools.utils.OgnlTools;
import net.sourceforge.jeval.Evaluator;
public class ExpressionTest {
    public static void main(String[] args) throws Exception {
        String content = "x-y";
        Map<String, BigDecimal> map = new HashMap<>();
        map.put("x", new BigDecimal("0.9"));
        map.put("y", new BigDecimal("1"));
        { // Java精度问题: 0.9-1=-0.09999999999999998
            double result = 0.9 - 1;
            System.out.printf("%-10s %s%n", "Java:", result);
        }
        { // Ognl支持BigDecimal: 0.9-1=-0.1
            Object result = OgnlTools.getValue(map, content);
            System.out.printf("%-10s %s%n", "Ognl:", result);
        }
        { // Jexl支持BigDecimal: 0.9-1=-0.1
            JexlContext context = new MapContext();
            for (Entry<String, BigDecimal> entry : map.entrySet()) {
                context.set(entry.getKey(), entry.getValue());
            }
            JexlEngine engine = new Engine();
            JexlExpression expression = engine.createExpression(content);
            Object result = expression.evaluate(context);
            System.out.printf("%-10s %s%n", "Jexl:", result);
        }
        { // MVEL支持BigDecimal: 0.9-1=-0.1
            Serializable expression = MVEL.compileExpression(content);
            Object result = MVEL.executeExpression(expression, map);
            System.out.printf("%-10s %s%n", "MVEL:", result);
        }
        { // JEPLite只支持double: 0.9-1=-0.09999999999999998
            JEP jep = new JEP();
            for (Entry<String, BigDecimal> entry : map.entrySet()) {
                jep.addVariable(entry.getKey(), entry.getValue().doubleValue());
            }
            jep.parseExpression(content);
            Object result = jep.getValue();
            System.out.printf("%-10s %s%n", "JEPLite:", result);
        }
        { // JEval表达式中的变量要用#{x}, 变量值只支持string, 会转换为double计算, 导致精度误差
            String string = "#{x}-#{y}";
            Evaluator evaluator = new Evaluator();
            for (Entry<String, BigDecimal> entry : map.entrySet()) {
                if (entry.getValue() != null) {
                    evaluator.putVariable(entry.getKey(), String.valueOf(entry.getValue()));
                }
            }
            Object result = evaluator.evaluate(string);
            System.out.printf("%-10s %s%n", "JEval:", result);
        }
        { // Janino不支持BigDecimal计算: 0.9-1=-0.09999999999999998
            List<String> keys = new ArrayList<>();
            List<Object> values = new ArrayList<>();
            List<Class<?>> types = new ArrayList<>();
            for (Entry<String, BigDecimal> entry : map.entrySet()) {
                if (entry.getValue() != null) {
                    keys.add(entry.getKey());
                    values.add(entry.getValue().doubleValue());
                    types.add(double.class);
                }
            }
            ExpressionEvaluator evaluator = new ExpressionEvaluator();
            evaluator.setParameters(keys.toArray(new String[0]), types.toArray(new Class<?>[0]));
            evaluator.cook(content);
            Object result = evaluator.evaluate(values.toArray());
            System.out.printf("%-10s %s%n", "Janino:", result);
        }
    }
}

涉及到的jar包

        <dependency>
            <groupId>ognl</groupId>
            <artifactId>ognl</artifactId>
            <version>3.2.18</version>
        </dependency>
        <dependency>
            <groupId>net.sourceforge.jeval</groupId>
            <artifactId>jeval</artifactId>
            <version>0.9.4</version>
        </dependency>
        <dependency>
            <groupId>org.cheffo</groupId>
            <artifactId>jeplite</artifactId>
            <version>0.8.7a</version>
        </dependency>
        <dependency>
            <groupId>janino</groupId>
            <artifactId>janino</artifactId>
            <version>2.5.10</version>
        </dependency>
        <dependency>
            <groupId>org.mvel</groupId>
            <artifactId>mvel2</artifactId>
            <version>2.4.12.Final</version>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-jexl3</artifactId>
            <version>3.1</version>
        </dependency>