jexl2 执行字符串Java代码

一，引入jar包，

<!-- https://mvnrepository.com/artifact/org.apache.commons/commons-jexl -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-jexl</artifactId>
<version>2.1.1</version>
</dependency>

二：案例：

        //
        JexlContext jc = new MapContext();
        jc.set("a", 1);
        jc.set("b", "0");
        jc.set("ans", new StringBuffer());
        Expression e = new JexlEngine().createExpression("while (a < 10) {a = a + 1; ans.append(a);}");
        e.evaluate(jc);
        System.out.println(jc.get("ans"));

        Expression expr;
        JexlContext ctxt = new MapContext();
        JexlEngine jexl = new JexlEngine();
        // 表达式
        String exps = "if(c1>c2) {c3=0}";
        expr = jexl.createExpression(exps);

        // case 1
        ctxt.set("c1", 1);
        ctxt.set("c2", 2);
        expr.evaluate(ctxt);
        System.out.println((Integer) ctxt.get("c3") == (Integer) (0));

        // case 2
        ctxt.set("c1", 2);
        ctxt.set("c2", 1);
        expr.evaluate(ctxt);
        System.out.println((Integer) ctxt.get("c3") == (Integer) (0));

MapContext 传入和取得变量。