@Autowired依赖项的成员为null

Question

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 Class：

@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);
}
}

我的用户类别：

@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，我的服务类别：

@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布线依赖关系在spring-boot中是如何工作的。在我的User类中，自动连接的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，beanTest及其成员的autowired User依赖项为null。与此相反，当我在User类中创建BeanTest对象时，一切都按预期进行。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，User类中的bean autowired是从容器中获取的，它是null。由于我在服务类中自动布线特定的用户依赖项，我不明白为什么它不起作用。有人能解释一下我是否以及如何正确地将BeanTest类自动连接到User类中吗。很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

当我自动连线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rest控制器来调用Service类中的函数
谢谢！！！

Answer 1

假设您在TimeOutConfig中自己创建BeanTest和User实例，请从BeanTest、BeanWebClient和User中删除所有@Component和@Autowired注释，如下所示：

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);
}
}

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);
}
}

public class User {
private BeanTest beanTest;
public User(BeanTest beanTest) {
this.beanTest=beanTest;
}

public User() {
//System.out.println("user create... hashCode :" + this.hashCode());
}
public void message() {
beanTest.message();
}
}