//通過id查詢女生的方法
@GetMapping(value?=?"/girls/{id}")
public?Girl?getGirl(@PathVariable("id")?Integer?id?){
????return?girlRepository.findOne(id);
}

//定義的接口
public?interface?GirlRepository?extends?JpaRepository<Girl,Integer>?{
????//通過年齡來查詢
????public?List<Girl>?findByAge(Integer?age);
}
findOne方法應該是默認使用注入的bean的主鍵來查詢，可以看一下實體類那個@id是不是加上了，下面是我的bean
package?com.imooc.demo.bean;

import?javax.persistence.Entity;
import?javax.persistence.GeneratedValue;
import?javax.persistence.Id;

@Entity
public?class?Girl?{

????@Id
????@GeneratedValue
????private?Integer?id;

????private?String?cupSize;

????private?Integer?age;

????public?Girl(){

????}

????public?Integer?getId()?{
????????return?id;
????}

????public?void?setId(Integer?id)?{
????????this.id?=?id;
????}

????public?String?getCupSize()?{
????????return?cupSize;
????}

????public?void?setCupSize(String?cupSize)?{
????????this.cupSize?=?cupSize;
????}

????public?Integer?getAge()?{
????????return?age;
????}

????public?void?setAge(Integer?age)?{
????????this.age?=?age;
????}
}