Spring Expression Language 简明教程
Spring SpEL - Array
SpEL 表达式支持访问数组并使用对象数组的索引。
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我们也可以在 SpEL 表达式中访问嵌套数组。
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：
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Employee.java − Employee class.
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Dept.java − Department class.
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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 String[] awards;
public String[] getAwards() {
return awards;
}
public void setAwards(String[] awards) {
this.awards = awards;
}
}以下 Dept.java 文件的内容：
package com.tutorialspoint;
public class Dept {
private Employee[] employees;
public Employee[] getEmployees() {
return employees;
}
public void setEmployees(Employee[] employees) {
this.employees = employees;
}
}以下 MainApp.java 文件的内容：
package com.tutorialspoint;
import java.text.ParseException;
import java.text.SimpleDateFormat;
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();
String[] awards = {"Star of the Month", "Champion", "Accelerator"};
employee.setAwards(awards);
Employee[] employees = { employee };
Dept dept = new Dept();
dept.setEmployees(employees);
EvaluationContext employeeContext = new StandardEvaluationContext(employee);
// evaluates to "Accelerator"
String award = parser.parseExpression("awards[2]").getValue(employeeContext, String.class);
System.out.println(award);
EvaluationContext deptContext = new StandardEvaluationContext(dept);
// evaluates to "Champion"
award = parser.parseExpression("employees[0].awards[1]").getValue(deptContext, String.class);
System.out.println(award);
}
}