java构造器复用方式

 public class Hello {
     public static void main(String[] args) {
         
     }
 }
 class EMployee{
     String name;
     char gender;
     int age;
     String job;
     double sal;
     // 职位 薪水
     public EMployee(String job,double sal) {
         this.job = job;
         this.sal = sal;
     }
     // 姓名 性别 年龄
     public EMployee(String name,char gender,int age) {
         this.name = name;
         this.gender = gender;
         this.age = age;
     }
     // 名字 性别 年龄 职位 薪水
     public EMployee(String job,double sal,String name,char gender,int age) {
         this(name,gender,age);
         this.job = job;
         this.sal = sal;
     }
 }

@Controller
public class FooController {
  @Autowired
  //@Inject
  private FooService fooService;
  
  //简单的使用例子，下同
  public List<Foo> listFoo() {
      return fooService.list();
  }
}

@Controller
public class FooController {
  
  private final FooService fooService;
  
  @Autowired
  public FooController(FooService fooService) {
      this.fooService = fooService;
  }
  
  //使用方式上同，略
}

@Controller
public class FooController {
  
  private FooService fooService;
  
  //使用方式上同，略
  @Autowired
  public void setFooService(FooService fooService) {
      this.fooService = fooService;
  }
}

//承接上面field注入的代码，假如客户端代码使用下面的调用(或者再Junit测试中使用)
//这里只是模拟一下，正常来说我们只会暴露接口给客户端，不会暴露实现。
FooController fooController = new FooController();
fooController.listFoo(); // -> NullPointerException

public class A {
    @Autowired
    private B b;
}
 
public class B {
    @Autowired
    private A a;
}