Spring Expression Language 简明教程
Spring SpEL - Constructor
SpEL 表达式支持使用 new 运算符在表达式中创建对象。我们需要传递类的完全限定名称。
Syntax
Employee robert = parser.parseExpression("new com.tutorialspoint.Employee('Robert','USA')").getValue(Employee.class);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.
-
Dept.java − Department 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;
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 Dept.java 文件的内容：
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 MainApp.java 文件的内容：
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);
}
}