此位置错误不允许使用注释@Bean

Question

我在一本书中读到，每当我们想要基于Java的配置并想要定义bean时，我们都会使用@Bean注释。但是当我这样做时，我得到了错误：The annotation @Bean is disallowed for this location。我的豆是：

package com.mj.cchp.bean;

import javax.validation.constraints.Digits;
import javax.validation.constraints.NotNull;

import org.springframework.context.annotation.Bean;

import com.mj.cchp.annotation.Email;

@Bean
public class UserBean {

    @NotNull
    @Email
    private String email;
    @NotNull
    private String firstName;
    @NotNull
    private String lastName;
    @Digits(fraction = 0, integer = 10)
    private String phoneNo;
    @NotNull
    private String role;

    public String getEmail() {
    return email;
    }

    public String getFirstName() {
    return firstName;
    }

    public String getLastName() {
    return lastName;
    }

    public String getPhoneNo() {
    return phoneNo;
    }

    public String getRole() {
    return role;
    }

    public void setEmail(String email) {
    this.email = email;
    }

    public void setFirstName(String firstName) {
    this.firstName = firstName;
    }

    public void setLastName(String lastName) {
    this.lastName = lastName;
    }

    public void setPhoneNo(String phoneNo) {
    this.phoneNo = phoneNo;
    }

    public void setRole(String role) {
    this.role = role;
    }
}

Answer 1

该@Bean注释是定义一个Bean在Spring容器被加载。它类似于指定的xml配置

<bean id="myId" class="..."/>

应该在Configuration文件（java）中使用。这与你的相似applicationContext.xml

@Configuration
@ComponentScan("...")
public class AppConfig{

   @Bean 
   public MyBean  myBean(){
      return new MyBean();
   }
}

在@Bean, @Configuration和其他新引入的注解会做的正是你在一个XML配置做什么。