Spring SpEL - 建構函式

SpEL 表示式支援使用 new 運算子在表示式中建立物件。我們需要傳遞類的全限定名。

語法

Employee robert = parser.parseExpression("new com.tutorialspoint.Employee('Robert','USA')").getValue(Employee.class);

以下示例展示了各種用例。

示例

讓我們更新在 Spring SpEL - 建立專案 章節中建立的專案。我們正在新增/更新以下檔案 -

• Employee.java - 員工類。

• Dept.java - 部門類。

• MainApp.java - 執行和測試的主應用程式。

以下是 Employee.java 檔案的內容 -

package com.tutorialspoint;

public class Employee {
   private String name;
   private String country;

   public Employee(String name, String country) {
      this.name = name;
      this.country = country;
   }
   public String getName() {
      return name;
   }
   public void setName(String name) {
      this.name = name;
   }
   public String getCountry() {
      return country;
   }
   public void setCountry(String country) {
      this.country = country;
   }
   public String toString() {
      return "[" +name+ ", "+country + "]";
   }
}

以下是 Dept.java 檔案的內容 -

package com.tutorialspoint;

import java.util.List;

public class Dept {
   private List<Employee> employees;

   public List<Employee> getEmployees() {
      return employees;
   }
   public void setEmployees(List<Employee> employees) {
      this.employees = employees;
   }
   public String toString() {
      return "[" + employees.toString() + "]";
   }
}

以下是 MainApp.java 檔案的內容 -

package com.tutorialspoint;

import java.text.ParseException;
import java.util.ArrayList;
import java.util.List;
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();

      List<Employee> employees = new ArrayList<Employee>();	   
      Employee robert = parser.parseExpression("new com.tutorialspoint.Employee('Robert','USA')")
         .getValue(Employee.class);
      employees.add(robert);

      Dept dept = new Dept();
      dept.setEmployees(employees);
      System.out.println(dept);

      EvaluationContext deptContext = new StandardEvaluationContext(dept);
      parser.parseExpression("employees.add(new com.tutorialspoint.Employee('Julie','USA'))")
         .getValue(deptContext);
      System.out.println(dept);
   }
}

輸出

[[[Robert, USA]]]
[[[Robert, USA], [Julie, USA]]]