Spring Expression Language 简明教程

Spring SpEL - Methods

SpEL 表达式支持访问某个对象的函数。

以下示例显示了各种使用案例。

Example

让我们更新在 Spring SpEL - Create Project 章节创建的项目。我们添加/更新了以下文件:

  1. Employee.java − Employee class.

  2. MainApp.java - 要运行和测试的主应用。

以下 Employee.java 文件的内容:

package com.tutorialspoint;

public class Employee {
   private List<String> awards;
   public List<String> getAwards() {
      return awards;
   }
   public void setAwards(List<String> awards) {
      this.awards = awards;
   }
   public boolean isAwardee() {
      return awards != null && awards.size() > 0;
   }
}

以下 MainApp.java 文件的内容:

package com.tutorialspoint;

import java.text.ParseException;
import java.util.Arrays;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.ExpressionParser;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;

public class MainApp {
   public static void main(String[] args) throws ParseException {
      ExpressionParser parser = new SpelExpressionParser();
      Employee employee = new Employee();
      employee.setAwards(Arrays.asList("Star of the Month", "Champion", "Accelerator"));
      EvaluationContext employeeContext = new StandardEvaluationContext(employee);

      // string literal, evaluates to "t"
      String t = parser.parseExpression("'Tutorials'.substring(2, 3)").getValue(String.class);
      System.out.println(t);

      // evaluates to true
      boolean isAwardee = parser.parseExpression("isAwardee()").getValue(employeeContext, Boolean.class);
      System.out.println(isAwardee);
   }
}

Output

t
true