Spring Expression Language 简明教程
Spring SpEL - Map
SpEL 表达式支持访问映射。
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:
-
Employee.java − Employee class.
-
MainApp.java - 要运行和测试的主应用。
以下 Employee.java 文件的内容:
package com.tutorialspoint;
import java.util.Map;
public class Employee {
private Map<String, String> offices;
public Map<String, String> getOffices() {
return offices;
}
public void setOffices(Map<String, String> offices) {
this.offices = offices;
}
}
以下 MainApp.java 文件的内容:
package com.tutorialspoint;
import java.text.ParseException;
import java.util.HashMap;
import java.util.Map;
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();
Map<String, String> officeMap = new HashMap();
officeMap.put("IN", "Hyderabad");
officeMap.put("UK", "London");
employee.setOffices(officeMap);
EvaluationContext employeeContext = new StandardEvaluationContext(employee);
// evaluates to "Hyderabad"
String city = parser.parseExpression("offices['IN']").getValue(employeeContext, String.class);
System.out.println(city);
}
}