Mastering Aviator: Advanced Java Expression Engine Examples

Environment: Java 8 + Aviator 5.2.5. Please read the previous article "Java Expression Evaluation Engine Aviator (Part 1)" first.

Example 8: Ternary Operator

<code>public class TernaryOperatorExample {
  public static void main(String[] args) {
    Map<String, Object> env = new HashMap<String, Object>();
    env.put("num", 100);
    String result = (String) AviatorEvaluator.execute("num > 998 ? 'yes':'no'", env);
    System.out.println(result);
  }
}</code>

Aviator's ternary expression does not require the two branches to have the same result type; they can be of any type, unlike Java.

Example 9: Regular Expression Matching

<code>public class RegularExpressionExample {
  public static void main(String[] args) {
    String email = "3487929**@qq.com";
    Map<String, Object> env = new HashMap<String, Object>();
    env.put("email", email);
    String username = (String) AviatorEvaluator.execute("email=~/([\\w0-8]+)@\\w+[\\.\\w+]+/ ? $1:'unknow'", env);
    System.out.println(username);
  }
}</code>

The =~ operator matches the string against the regex; the result is Boolean, which can be used in a ternary expression. If the match succeeds, $1 returns the first capture group (the username), otherwise "unknown" is returned. This example prints the username part of the email.

Aviator supports regex literals enclosed in //, which can be used for matching, comparison, and only work with strings. Successful matches populate $0 with the whole match, $1 with the first group, and so on. Internally Aviator uses java.util.regex.Pattern, so the syntax is identical to Java.

Example 10: Variable Sugar

Aviator provides a convenient syntax sugar for accessing object properties:

a.b

accesses property

b

of variable

a

, and

a.b.c

accesses nested properties.

<code>public class Person {
  private String name;
  private Integer age;
  public Person(String name, Integer age) {
    this.name = name;
    this.age = age;
  }
  public String getName() { return name; }
  public void setName(String name) { this.name = name; }
  public Integer getAge() { return age; }
  public void setAge(Integer age) { this.age = age; }
}

public class VariableExample {
  public static void main(String[] args) {
    Person person = new Person("张三", 20);
    Map<string, object=""> env = new HashMap<string, object="">();
    env.put("person", person);
    String result = (String) AviatorEvaluator.execute("'[Person name = ' + person.name + ' age = ' + person.age + ']'",</string,></string,></code>