java -version 2>&1
mvn -v | head -3

openjdk version "17.0.20.1" 2026-08-18
OpenJDK Runtime Environment (build 17.0.20.1+1-1-22.04-Ubuntu)
OpenJDK 64-Bit Server VM (build 17.0.20.1+1-1-22.04-Ubuntu, mixed mode, sharing)
Apache Maven 3.6.3
Maven home: /usr/share/maven
Java version: 17.0.20.1, vendor: Ubuntu, runtime: /usr/lib/jvm/java-17-openjdk-amd64

mkdir -p /opt/jexl-demo/src/main/java/demo

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>demo</groupId>
  <artifactId>jexl-demo</artifactId>
  <version>1.0.0</version>
  <packaging>jar</packaging>
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.release>17</maven.compiler.release>
  </properties>
  <dependencies>
    <dependency>
      <groupId>org.apache.commons</groupId>
      <artifactId>commons-jexl3</artifactId>
      <version>3.7.0</version>
    </dependency>
  </dependencies>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.11.0</version>
        <configuration>
          <release>17</release>
        </configuration>
      </plugin>
    </plugins>
  </build>
</project>

cd /opt/jexl-demo && mvn compile
mvn dependency:build-classpath -Dmdep.outputFile=cp.txt -q && cat cp.txt

[INFO] Compiling 8 source files with javac [debug release 17] to target/classes
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.805 s
[INFO] Finished at: 2026-10-14T10:22:34Z
[INFO] ------------------------------------------------------------------------

/root/.m2/repository/org/apache/commons/commons-jexl3/3.7.0/commons-jexl3-3.7.0.jar:/root/.m2/repository/commons-logging/commons-logging/1.4.0/commons-logging-1.4.0.jar

cd /opt/jexl3-dist && javap -cp commons-jexl3-3.7.0.jar org.apache.commons.jexl3.JexlBuilder | grep -Ei "function|namespace|permission"

  public java.util.Map<java.lang.String, java.lang.Object> namespaces();
  public org.apache.commons.jexl3.JexlBuilder namespaces(java.util.Map<java.lang.String, java.lang.Object>);
  public org.apache.commons.jexl3.introspection.JexlPermissions permissions();
  public org.apache.commons.jexl3.JexlBuilder permissions(org.apache.commons.jexl3.introspection.JexlPermissions);

// 方式一：默认引擎（本文多数示例使用；3.7.0 默认权限收紧，自定义类反射被拒）
JexlEngine jexl = new org.apache.commons.jexl3.JexlBuilder().create();

// 方式二：放开反射权限的引擎（POJO 导航、命名空间函数示例使用）
JexlEngine jexl2 = new org.apache.commons.jexl3.JexlBuilder()
        .permissions(org.apache.commons.jexl3.introspection.JexlPermissions.UNRESTRICTED)
        .create();

package demo;

import org.apache.commons.jexl3.JexlEngine;
import org.apache.commons.jexl3.JexlExpression;
import org.apache.commons.jexl3.MapContext;

/** 算术、字符串、三元表达式求值 */
public class BasicEval {
    public static void main(String[] args) {
        JexlEngine jexl = new org.apache.commons.jexl3.JexlBuilder().create();
        Object r1 = jexl.createExpression("1 + 2 * 3").evaluate(null);
        System.out.println("1 + 2 * 3 = " + r1);

        Object r2 = jexl.createExpression("(1 + 2) * 3").evaluate(null);
        System.out.println("(1 + 2) * 3 = " + r2);

        Object r3 = jexl.createExpression("10 / 4").evaluate(null);
        System.out.println("10 / 4 = " + r3);

        Object r4 = jexl.createExpression("10 % 3").evaluate(null);
        System.out.println("10 % 3 = " + r4);

        // 字符串拼接
        Object r5 = jexl.createExpression("'Hello, ' + 'JEXL' + ' 3.7.0'").evaluate(null);
        System.out.println("concat: " + r5);

        // 三元表达式
        Object r6 = jexl.createExpression("5 > 3 ? 'yes' : 'no'").evaluate(null);
        System.out.println("ternary: " + r6);

        // 逻辑与比较
        Object r7 = jexl.createExpression("!(5 > 3) && (2 == 2)").evaluate(null);
        System.out.println("logic: " + r7);

        // 字符串方法
        Object r8 = jexl.createExpression("'jexl-demo'.toUpperCase()").evaluate(null);
        System.out.println("string method: " + r8);
    }
}

cd /opt/jexl-demo
CP="target/classes:$(cat cp.txt)" && java -Dfile.encoding=UTF-8 -cp "$CP" demo.BasicEval

1 + 2 * 3 = 7
(1 + 2) * 3 = 9
10 / 4 = 2
10 % 3 = 1
concat: Hello, JEXL 3.7.0
ternary: yes
logic: false
string method: JEXL-DEMO

package demo;

import org.apache.commons.jexl3.JexlContext;
import org.apache.commons.jexl3.JexlEngine;
import org.apache.commons.jexl3.JexlScript;
import org.apache.commons.jexl3.MapContext;

/** JexlScript 多语句脚本：var 声明、return */
public class ScriptDemo {
    public static void main(String[] args) {
        JexlEngine jexl = new org.apache.commons.jexl3.JexlBuilder().create();
        JexlContext ctx = new MapContext();
        ctx.set("n", 10);

        // 多语句：var 声明 + 循环 + return
        JexlScript factorial = jexl.createScript(
                "var result = 1;" +
                "for (var i = 2; i <= n; i = i + 1) {" +
                "  result = result * i;" +
                "}" +
                "return result;"
        );
        System.out.println("factorial(10) = " + factorial.execute(ctx));

        // 带参数的脚本
        JexlScript add = jexl.createScript("(a, b) -> { return a + b; }");
        System.out.println("lambda add(3,4) = " + add.execute(null, 3, 4));

        // 函数定义脚本
        JexlScript func = jexl.createScript(
                "function fib(n) {" +
                "  if (n <= 1) return n;" +
                "  return fib(n - 1) + fib(n - 2);" +
                "} fib(15)"
        );
        System.out.println("fib(15) = " + func.execute(new MapContext()));

        // 脚本赋值到 context
        JexlScript assign = jexl.createScript("var half = n / 2; half");
        System.out.println("half = " + assign.execute(ctx));
    }
}

cd /opt/jexl-demo
CP="target/classes:$(cat cp.txt)" && java -Dfile.encoding=UTF-8 -cp "$CP" demo.ScriptDemo

factorial(10) = 3628800
lambda add(3,4) = 7
fib(15) = 610
half = 5

package demo;

import org.apache.commons.jexl3.JexlContext;
import org.apache.commons.jexl3.JexlEngine;
import org.apache.commons.jexl3.JxltEngine;
import org.apache.commons.jexl3.MapContext;

import java.io.StringWriter;

/** JxltEngine 模板功能："Hello ${name}" */
public class TemplateDemo {
    public static void main(String[] args) {
        JexlEngine jexl = new org.apache.commons.jexl3.JexlBuilder()
                .permissions(org.apache.commons.jexl3.introspection.JexlPermissions.UNRESTRICTED)
                .create();
        JxltEngine jxlt = jexl.createJxltEngine();

        JexlContext ctx = new MapContext();
        ctx.set("name", "JEXL 3.7.0");
        ctx.set("user", new PojoNav.Person("李四", 25));

        // 简单插值
        JxltEngine.Template t1 = jxlt.createTemplate("Hello ${name}!");
        StringWriter w1 = new StringWriter();
        t1.evaluate(ctx, w1);
        System.out.println("template1: " + w1);

        // 带表达式的插值
        JxltEngine.Template t2 = jxlt.createTemplate("${user.name} 的年龄是 ${user.age}，${user.age >= 18 ? '已成年' : '未成年'}");
        StringWriter w2 = new StringWriter();
        t2.evaluate(ctx, w2);
        System.out.println("template2: " + w2);

        // if 指令模板：3.7.0 模板指令为 $$ 行前缀（createTemplate 默认 prefix "$$"），不再支持旧式 %{...}
        JxltEngine.Template t3 = jxlt.createTemplate(
                "$$ if (user.age >= 18) {\n" +
                "成年人\n" +
                "$$ } else {\n" +
                "未成年人\n" +
                "$$ }\n" +
                "：${user.name}"
        );
        StringWriter w3 = new StringWriter();
        t3.evaluate(ctx, w3);
        System.out.println("template3: " + w3.toString().replace("\n", "\\n"));

        // for 指令模板
        ctx.set("items", new String[]{"a", "b", "c"});
        JxltEngine.Template t4 = jxlt.createTemplate(
                "$$ for (var it : items) {\n" +
                "[${it}]\n" +
                "$$ }\n"
        );
        StringWriter w4 = new StringWriter();
        t4.evaluate(ctx, w4);
        System.out.println("template4: " + w4.toString().replace("\n", "\\n"));
    }
}

cd /opt/jexl-demo
CP="target/classes:$(cat cp.txt)" && java -Dfile.encoding=UTF-8 -cp "$CP" demo.TemplateDemo

template1: Hello JEXL 3.7.0!
template2: 李四 的年龄是 25，已成年
template3: 成年人\n：李四
template4: [a]\n[b]\n[c]\n

package demo;

import org.apache.commons.jexl3.JexlBuilder;
import org.apache.commons.jexl3.JexlEngine;
import org.apache.commons.jexl3.JexlException;
import org.apache.commons.jexl3.MapContext;
import org.apache.commons.jexl3.introspection.JexlPermissions;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/** JexlPermissions 安全权限：RESTRICTED 与自定义白名单阻断危险类调用 */
public class PermissionDemo {
    public static void main(String[] args) {
        String sysExpr = "System.getProperty('user.dir')";

        // 1. 对照：表达式里直接写类名 System.getProperty(...) 时，System 被当作未定义变量 -> null
        //    （JEXL 访问静态方法须用命名空间 ns:method 形式，不能裸写类名导航）
        JexlEngine open = new JexlBuilder()
                .permissions(JexlPermissions.UNRESTRICTED)
                .create();
        Object r1 = open.createExpression(sysExpr).evaluate(new MapContext());
        System.out.println("UNRESTRICTED 引擎 System.getProperty('user.dir') -> " + r1 + "  (System 是未定义变量)");

        // 2. RESTRICTED 引擎同表达式同样返回 null
        JexlEngine restricted = new JexlBuilder()
                .permissions(JexlPermissions.RESTRICTED)
                .create();
        Object r2 = restricted.createExpression(sysExpr).evaluate(new MapContext());
        System.out.println("RESTRICTED 引擎同表达式 -> " + r2);

        // 3. RESTRICTED 白名单内的类（String/Math 等）正常工作
        Object r3 = restricted.createExpression("'abc'.length()").evaluate(new MapContext());
        System.out.println("RESTRICTED 引擎 'abc'.length() -> " + r3);

        // 4. RESTRICTED 下命名空间调用自定义类方法 -> 被拒抛 JexlException$Method
        Map<String, Object> fns = new HashMap<>();
        fns.put("util", new FunctionNS.Strings());
        JexlEngine restrictedNs = new JexlBuilder()
                .permissions(JexlPermissions.RESTRICTED)
                .namespaces(fns)
                .create();
        try {
            Object r4 = restrictedNs.createExpression("util:reverse('abc')").evaluate(new MapContext());
            System.out.println("RESTRICTED 命名空间调用竟然成功: " + r4);
        } catch (JexlException e) {
            System.out.println("RESTRICTED 拒绝自定义类方法调用 -> " + e.getClass().getName());
            System.out.println("异常消息: " + e.getMessage());
        }

        // 5. 默认引擎（不设 permissions）行为等价 RESTRICTED：自定义 POJO 属性导航报 undefined property
        JexlEngine defaultEngine = new JexlBuilder().create();
        MapContext pctx = new MapContext();
        pctx.set("person", new PojoNav.Person("王五", 30));
        try {
            Object r5 = defaultEngine.createExpression("person.name").evaluate(pctx);
            System.out.println("默认引擎 POJO 竟然成功: " + r5);
        } catch (JexlException e) {
            System.out.println("默认引擎拒绝 POJO 属性导航 -> " + e.getClass().getName());
            System.out.println("异常消息: " + e.getMessage());
        }

        // 6. 自定义白名单 parse("java.util.*")：ArrayList 可用，String 被拒
        JexlEngine custom = new JexlBuilder()
                .permissions(JexlPermissions.parse("java.util.*"))
                .create();
        MapContext ctx = new MapContext();
        List<String> list = new ArrayList<>();
        ctx.set("list", list);
        Object r6 = custom.createExpression("list.add('x') && list.size() == 1").evaluate(ctx);
        System.out.println("自定义白名单(java.util.*) ArrayList -> " + r6);
        Object r7 = custom.createExpression("'abc'.length()").evaluate(ctx);
        System.out.println("自定义白名单 String.length() -> " + r7 + "  (String 不在 java.util.*, 被拒返回 null)");
    }
}

cd /opt/jexl-demo
CP="target/classes:$(cat cp.txt)" && java -Dfile.encoding=UTF-8 -cp "$CP" demo.PermissionDemo

UNRESTRICTED 引擎 System.getProperty('user.dir') -> null  (System 是未定义变量)
RESTRICTED 引擎同表达式 -> null
RESTRICTED 引擎 'abc'.length() -> 3
RESTRICTED 拒绝自定义类方法调用 -> org.apache.commons.jexl3.JexlException$Method
异常消息: demo.PermissionDemo.main:46@1:13 unsolvable function/method 'reverse(String)'
默认引擎拒绝 POJO 属性导航 -> org.apache.commons.jexl3.JexlException$Property
异常消息: demo.PermissionDemo.main:58@1:11 undefined property 'name'
自定义白名单(java.util.*) ArrayList -> true
自定义白名单 String.length() -> null  (String 不在 java.util.*, 被拒返回 null)

package demo;

import org.apache.commons.jexl3.JexlEngine;
import org.apache.commons.jexl3.JexlExpression;
import org.apache.commons.jexl3.MapContext;

import java.util.HashMap;
import java.util.Map;

/** JexlContext 变量注入与读取（MapContext） */
public class ContextVar {
    public static void main(String[] args) {
        JexlEngine jexl = new org.apache.commons.jexl3.JexlBuilder().create();

        Map<String, Object> vars = new HashMap<>();
        vars.put("x", 7);
        vars.put("y", 6);
        MapContext ctx = new MapContext(vars);
        ctx.set("greeting", "你好");

        Object r1 = jexl.createExpression("x * y").evaluate(ctx);
        System.out.println("x * y = " + r1);

        Object r2 = jexl.createExpression("greeting + ', JEXL'").evaluate(ctx);
        System.out.println("greeting = " + r2);

        // 变量读写
        ctx.set("x", 100);
        Object r3 = jexl.createExpression("x + y").evaluate(ctx);
        System.out.println("after set x=100, x + y = " + r3);

        // 注：3.7.0 默认禁止脚本对未声明全局变量赋值（z = x*y 会抛 JexlException$Feature），
        // 使用 var 声明局部变量
        Object r4 = jexl.createScript("var z = x * y; return z * 2;").execute(ctx);
        System.out.println("script var z = x*y, return z*2 = " + r4);

        // Map 变量的成员访问
        Map<String, Object> user = new HashMap<>();
        user.put("name", "Alice");
        user.put("score", 92);
        ctx.set("user", user);
        Object r5 = jexl.createExpression("user.name + ' score=' + user.score").evaluate(ctx);
        System.out.println("map access: " + r5);
    }
}

cd /opt/jexl-demo
CP="target/classes:$(cat cp.txt)" && java -Dfile.encoding=UTF-8 -cp "$CP" demo.ContextVar

x * y = 42
greeting = 你好, JEXL
after set x=100, x + y = 106
script var z = x*y, return z*2 = 1200
map access: Alice score=92

package demo;

import org.apache.commons.jexl3.JexlEngine;
import org.apache.commons.jexl3.JexlExpression;
import org.apache.commons.jexl3.MapContext;

/** 自定义 POJO 属性导航与方法调用 */
public class PojoNav {
    public static class Person {
        private final String name;
        private final int age;

        public Person(String name, int age) {
            this.name = name;
            this.age = age;
        }

        public String getName() { return name; }
        public int getAge() { return age; }
        public String greet() { return "你好, 我是 " + name + ", 今年 " + age + " 岁"; }
        public boolean isAdult() { return age >= 18; }
    }

    public static void main(String[] args) {
        // 实测：3.7.0 默认引擎（未设 permissions）对自定义 POJO 属性导航报 undefined property，
        // 需显式放开为 UNRESTRICTED 才能访问 demo 类的 getter
        JexlEngine jexl = new org.apache.commons.jexl3.JexlBuilder()
                .permissions(org.apache.commons.jexl3.introspection.JexlPermissions.UNRESTRICTED)
                .create();
        MapContext ctx = new MapContext();
        ctx.set("person", new Person("张三", 20));
        ctx.set("child", new Person("小明", 12));

        Object r1 = jexl.createExpression("person.name").evaluate(ctx);
        System.out.println("person.name = " + r1);

        Object r2 = jexl.createExpression("person.age").evaluate(ctx);
        System.out.println("person.age = " + r2);

        Object r3 = jexl.createExpression("person.greet()").evaluate(ctx);
        System.out.println("person.greet() = " + r3);

        Object r4 = jexl.createExpression("person.age > 18 ? '成年' : '未成年'").evaluate(ctx);
        System.out.println("person ternary = " + r4);

        Object r5 = jexl.createExpression("child.age > 18 ? '成年' : '未成年'").evaluate(ctx);
        System.out.println("child ternary = " + r5);

        Object r6 = jexl.createExpression("person.isAdult()").evaluate(ctx);
        System.out.println("person.isAdult() = " + r6);
    }
}

cd /opt/jexl-demo
CP="target/classes:$(cat cp.txt)" && java -Dfile.encoding=UTF-8 -cp "$CP" demo.PojoNav

person.name = 张三
person.age = 20
person.greet() = 你好, 我是 张三, 今年 20 岁
person ternary = 成年
child ternary = 未成年
person.isAdult() = true

Exception in thread "main" org.apache.commons.jexl3.JexlException$Property: demo.PojoNav.main:30@1:11 undefined property 'name'
        at demo.PojoNav.main(PojoNav.java:30)

package demo;

import org.apache.commons.jexl3.JexlEngine;
import org.apache.commons.jexl3.MapContext;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/** 集合：数组/Map 下标访问、size()、for 循环脚本 */
public class CollectionEval {
    public static void main(String[] args) {
        JexlEngine jexl = new org.apache.commons.jexl3.JexlBuilder().create();
        MapContext ctx = new MapContext();

        List<String> list = new ArrayList<>();
        list.add("apple");
        list.add("banana");
        list.add("cherry");
        ctx.set("list", list);

        int[] arr = {10, 20, 30};
        ctx.set("arr", arr);

        Map<String, Integer> prices = new HashMap<>();
        prices.put("apple", 5);
        prices.put("banana", 3);
        ctx.set("prices", prices);

        // 列表下标
        System.out.println("list[0] = " + jexl.createExpression("list[0]").evaluate(ctx));
        System.out.println("list.get(2) = " + jexl.createExpression("list.get(2)").evaluate(ctx));
        System.out.println("list.size() = " + jexl.createExpression("list.size()").evaluate(ctx));

        // 数组下标
        System.out.println("arr[1] = " + jexl.createExpression("arr[1]").evaluate(ctx));

        // Map 下标与属性式访问
        System.out.println("prices['apple'] = " + jexl.createExpression("prices['apple']").evaluate(ctx));
        System.out.println("prices.banana = " + jexl.createExpression("prices.banana").evaluate(ctx));

        // for 循环（脚本块），3.7.0 需用 var 声明局部变量
        Object sum = jexl.createScript(
                "var total = 0; for(var item : arr) { total = total + item; } return total;"
        ).execute(ctx);
        System.out.println("for-sum(arr) = " + sum);

        Object joined = jexl.createScript(
                "var sb = ''; for(var f : list) { sb = sb + f + ','; } return sb;"
        ).execute(ctx);
        System.out.println("for-join(list) = " + joined);

        // 三目 + 集合组合
        Object r = jexl.createExpression("list.size() > 2 ? '列表够大' : '列表太小'").evaluate(ctx);
        System.out.println("size ternary = " + r);
    }
}

cd /opt/jexl-demo
CP="target/classes:$(cat cp.txt)" && java -Dfile.encoding=UTF-8 -cp "$CP" demo.CollectionEval

list[0] = apple
list.get(2) = cherry
list.size() = 3
arr[1] = 20
prices['apple'] = 5
prices.banana = 3
for-sum(arr) = 60
for-join(list) = apple,banana,cherry,
size ternary = 列表够大

Exception in thread "main" org.apache.commons.jexl3.JexlException$Feature: @1:1 global assign/modify error in 'z'
        at org.apache.commons.jexl3.parser.FeatureController.throwFeatureException(FeatureController.java:107)
        at org.apache.commons.jexl3.parser.FeatureController.controlSideEffect(FeatureController.java:54)
        ...
        at org.apache.commons.jexl3.JexlEngine.createScript(JexlEngine.java:423)
        at demo.ContextVar.main(ContextVar.java:33)

Exception in thread "main" org.apache.commons.jexl3.JexlException$Feature: @1:1 global assign/modify error in 'total'
        at org.apache.commons.jexl3.parser.FeatureController.throwFeatureException(FeatureController.java:107)
        ...
        at demo.CollectionEval.main(CollectionEval.java:44)

package demo;

import org.apache.commons.jexl3.JexlContext;
import org.apache.commons.jexl3.JexlEngine;
import org.apache.commons.jexl3.MapContext;

import java.util.HashMap;
import java.util.Map;

/** 自定义函数命名空间：JexlBuilder.namespaces，表达式里用 ns:method(...) 调用 */
public class FunctionNS {
    /** 静态工具类，注册为命名空间 */
    public static class Strings {
        public static String reverse(String s) {
            return new StringBuilder(s).reverse().toString();
        }
        public static int length(String s) {
            return s.length();
        }
    }

    public static class Maths {
        public static int square(int x) {
            return x * x;
        }
    }

    public static void main(String[] args) {
        Map<String, Object> funcs = new HashMap<>();
        funcs.put("str", new FunctionNS.Strings());
        funcs.put("m", new FunctionNS.Maths());

        JexlEngine jexl = new org.apache.commons.jexl3.JexlBuilder()
                .permissions(org.apache.commons.jexl3.introspection.JexlPermissions.UNRESTRICTED)
                .namespaces(funcs)
                .create();

        JexlContext ctx = new MapContext();
        ctx.set("word", "jexl");

        System.out.println("str:reverse(word) = " + jexl.createExpression("str:reverse(word)").evaluate(ctx));
        System.out.println("str:length('apache') = " + jexl.createExpression("str:length('apache')").evaluate(ctx));
        System.out.println("m:square(9) = " + jexl.createExpression("m:square(9)").evaluate(ctx));

        // 组合：命名空间函数 + 原生运算
        System.out.println("组合 = " + jexl.createExpression("m:square(3) + str:length(word)").evaluate(ctx));
    }
}

cd /opt/jexl-demo
CP="target/classes:$(cat cp.txt)" && java -Dfile.encoding=UTF-8 -cp "$CP" demo.FunctionNS

str:reverse(word) = lxej
str:length('apache') = 6
m:square(9) = 81
组合 = 13

[ERROR] /opt/jexl-demo/src/main/java/demo/FunctionNS.java:[34,17] cannot find symbol
[ERROR]   symbol:   method setFunctions(java.util.Map<java.lang.String,java.lang.Object>)
[ERROR]   location: class org.apache.commons.jexl3.JexlBuilder

Exception in thread "main" org.apache.commons.jexl3.JexlException$Method: demo.FunctionNS.main:40@1:12 unsolvable function/method 'reverse(String)'
        at demo.FunctionNS.main(FunctionNS.java:40)

template3: %{if(user.age >= 18)}成年人%{else}未成年人%{end}：李四
Exception in thread "main" org.apache.commons.jexl3.JexlException$Variable: demo.TemplateDemo.main:44@1:1 variable 'it' is undefined
        at demo.TemplateDemo.main(TemplateDemo.java:46)

Exception in thread "main" org.apache.commons.jexl3.JexlException$Parsing: demo.TemplateDemo.main:35@1:1 parsing error in 'if'
        at org.apache.commons.jexl3.JxltEngine.createTemplate(JxltEngine.java:371)
        at org.apache.commons.jexl3.JxltEngine.createTemplate(JxltEngine.java:404)
        at demo.TemplateDemo.main(TemplateDemo.java:35)