【发布时间】：2021-11-13 09:15:31
【问题描述】：
我的配置类：
@Configuration
public class TimeOutConfig {
@Value("${value1}")
private int value1;
@Value("${value2}")
private int value2;
@Bean()
User boTimeOut() {
System.out.println("In BOTimeOutConfig");
BeanTest b1 = new BeanTest(value1, value2);
User u1 = new User(b1);
return u1;
}
@Value("${value3}")
private int value3;
@Value("${value4}")
private int value4;
@Bean(name = "BSETimeout")
User getBSEUser() {
System.out.println("In BSETimeOutConfig");
User u2 = new User( new BeanTest(value3, value4));
return u2;
}
}
BeanTest 类：
@Component
public class BeanTest {
private int v1;
private int v2;
BeanWebClient b1;
public BeanTest(){}
public BeanTest(int v1, int v2){
this.v1=v1;
this.v2=v2;
beanWebClient();
}
public BeanWebClient beanWebClient() {
//System.out.println("In BeanTest class beanWebClient() method execution v1 and v2: "+v1+v2);
b1 = new BeanWebClient(v1,v2);
System.out.println("In BeanTest class beanWebClient() method execution v1 and v2: "+b1.getV1()+" "+b1.getV2());
return b1;
}
public void message()
{
b1.webClientMessage();
//System.out.println("V1= "+v1+" V2= "+v2);
}
}
BeanWebClient 类：
@Component
public class BeanWebClient {
private int v1;
private int v2;
public BeanWebClient(int v1, int v2){
this.v1=v1;
this.v2=v2;
System.out.println("Received from BeanTest "+v1+" "+v2);
}
public BeanWebClient(){
}
public int getV1() {
return v1;
}
public int getV2() {
return v2;
}
public void webClientMessage(){
System.out.println("In BeanWebClient class, printing from autowired dependency "+v1+" "+v2);
}
}
我的用户类：
@Component
public class User {
@Autowired
private BeanTest beanTest;
public User(BeanTest beanTest){
this.beanTest=beanTest;
}
public void message()
{
beanTest.message();
}
public User() {
//System.out.println("user create... hashCode :" + this.hashCode());
}
}
最后，我的服务类：
@Service
public class BeanService {
@Autowired
@Qualifier("boTimeOut")
private User boUser;
@Autowired
@Qualifier("BSETimeout")
private User bseUser;
public void printBO()
{
boUser.message();
}
public void printBSE()
{
bseUser.message();
}
}
我试图了解组件和自动装配依赖项在 Spring Boot 中是如何工作的。在我的 User 类中，自动装配的 BeanTest 类在配置期间被初始化——所有必要的打印语句都被执行。但是当我调用 Service 类的函数时，自动装配的 User 依赖项对于 beanTest 及其成员为 null。与此相反，当我在我的 User 类中创建 BeanTest 对象时，一切都按预期工作。这就是我的意思：
@Component
public class User {
BeanTest beanTest;
public User(BeanTest beanTest){
this.beanTest=beanTest;
}
public void message()
{
beanTest.message();
}
public User() {
//System.out.println("user create... hashCode :" + this.hashCode());
}
}
我有点理解在 User 类中自动装配的 bean 是从容器中获取的，它是 null。由于我在我的服务类中自动装配特定的用户依赖项，我不明白为什么它不起作用。 有人可以解释一下是否以及如何正确地将 BeanTest 类自动连接到 User 类中。 抱歉，有这么多代码文件。
输出 这是我在没有@Autowire 的情况下手动创建 BeanTest 对象时得到的输出
In BOTimeOutConfig
Received from BeanTest 10 20
In BeanTest class beanWebClient() method execution v1 and v2: 10 20
In BSETimeOutConfig
Received from BeanTest 30 40
In BeanTest class beanWebClient() method execution v1 and v2: 30 40
2021-11-13 14:37:58.161 WARN 404383 --- [ main] JpaBaseConfiguration$JpaWebConfiguration : spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning
2021-11-13 14:37:58.613 INFO 404383 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2021-11-13 14:37:58.622 INFO 404383 --- [ main] c.paytmmoney.errordb.ErrordbApplication : Started ErrordbApplication in 4.04 seconds (JVM running for 4.379)
2021-11-13 14:38:07.768 INFO 404383 --- [nio-8080-exec-1] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'
2021-11-13 14:38:07.768 INFO 404383 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2021-11-13 14:38:07.769 INFO 404383 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet : Completed initialization in 1 ms
In /test method
In BeanWebClient class, printing from autowired dependency 10 20
In /test method
In BeanWebClient class, printing from autowired dependency 30 40
当我自动装配 BeanTest 类时，这是输出：
In BOTimeOutConfig
Received from BeanTest 10 20
In BeanTest class beanWebClient() method execution v1 and v2: 10 20
In BSETimeOutConfig
Received from BeanTest 30 40
In BeanTest class beanWebClient() method execution v1 and v2: 30 40
2021-11-13 14:40:36.072 WARN 404724 --- [ main] JpaBaseConfiguration$JpaWebConfiguration : spring.jpa.open-in-view is enabled by default. Therefore, database queries may be performed during view rendering. Explicitly configure spring.jpa.open-in-view to disable this warning
2021-11-13 14:40:36.585 INFO 404724 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2021-11-13 14:40:36.596 INFO 404724 --- [ main] c.paytmmoney.errordb.ErrordbApplication : Started ErrordbApplication in 4.353 seconds (JVM running for 4.75)
2021-11-13 14:40:45.081 INFO 404724 --- [nio-8080-exec-2] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring DispatcherServlet 'dispatcherServlet'
2021-11-13 14:40:45.081 INFO 404724 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Initializing Servlet 'dispatcherServlet'
2021-11-13 14:40:45.082 INFO 404724 --- [nio-8080-exec-2] o.s.web.servlet.DispatcherServlet : Completed initialization in 1 ms
In /test method
2021-11-13 14:40:45.204 ERROR 404724 --- [nio-8080-exec-2] o.a.c.c.C.[.[.[/].[dispatcherServlet] : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause
java.lang.NullPointerException: null
at com.paytmmoney.errordb.repository.BeanTest.message(BeanTest.java:42) ~[main/:na]
at com.paytmmoney.errordb.repository.User.message(User.java:22) ~[main/:na]
at com.paytmmoney.errordb.service.BeanService.printBO(BeanService.java:21) ~[main/:na]
我正在使用休息控制器来调用服务类中的函数。
谢谢！！！
【问题讨论】：
-
您正在混合字段注入 (@Autowired) 和构造函数注入。你的项目看起来很乱。您能否在 Github 上提供一个可重现的最小示例？
-
@SimonMartinelli 我在这里添加了代码 - github.com/Aditya149349/StackOverflow 非常感谢您的帮助！
-
有很多问题。为什么要在服务中使用限定符？
-
我必须同意@SimonMartinelli，您的代码很难遵循。您在
TimeOutConfig文件中创建Userbean，但随后您还使用@Component注释User类（实际上是“创建”一个bean）。此外，问题似乎并不在于您的beanTest在您的User对象中为空。问题似乎出在BeanTest.message()方法中。b1很可能为空。您是否尝试过从BeanTest、BeanWebClient和User类中删除@Component注释，因为它们似乎与您正在尝试做的事情无关。 -
抱歉，没有，因为我不知道预期会发生什么，因为您没有提供有关代码的上下文。
标签： java spring-boot javabeans autowired