如何解决Springboot：扫描bean时失败
我试图理解springboot中的一个概念。
我的项目结构如下所述。有两个软件包，每个软件包都有一个类。
src/main/java
> com.emerald.paymentengine
ApplicationRun.java
> com.emerald.paymentengine.config
DataSourceDbConfig.java
当我尝试按照上述结构运行ApplicationRun.java时，出现以下错误：
错误：
2020-08-19 01:33:08.673 INFO 30128 --- [ restartedMain] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2020-08-19 01:33:08.673 INFO 30128 --- [ restartedMain] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.37]
2020-08-19 01:33:08.749 INFO 30128 --- [ restartedMain] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2020-08-19 01:33:08.750 INFO 30128 --- [ restartedMain] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 657 ms
2020-08-19 01:33:08.779 WARN 30128 --- [ restartedMain] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'applicationRun': Unsatisfied dependency expressed through constructor parameter 0; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'com.emerlad.paymentengine.config.DataSourceDbConfig' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}
2020-08-19 01:33:08.781 INFO 30128 --- [ restartedMain] o.apache.catalina.core.StandardService : Stopping service [Tomcat]
2020-08-19 01:33:08.791 INFO 30128 --- [ restartedMain] ConditionEvaluationReportLoggingListener :
Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2020-08-19 01:33:08.883 ERROR 30128 --- [ restartedMain] o.s.b.d.LoggingFailureAnalysisReporter :
***************************
APPLICATION FAILED TO START
***************************
Description:
Parameter 0 of constructor in com.emerald.paymentengine.ApplicationRun required a bean of type 'com.emerlad.paymentengine.config.DataSourceDbConfig' that could not be found.
Action:
Consider defining a bean of type 'com.emerlad.paymentengine.config.DataSourceDbConfig' in your configuration.
但是当我将DataSourceDbConfig.java移到与下面提到的相同的程序包中时，它正在运行，并且输出如下：
src/main/java
> com.emerald.paymentengine
ApplicationRun.java
DataSourceDbConfig.java
输出：
2020-08-19 01:37:24.726 INFO 34364 --- [ restartedMain] o.apache.catalina.core.StandardService : Starting service [Tomcat]
2020-08-19 01:37:24.726 INFO 34364 --- [ restartedMain] org.apache.catalina.core.StandardEngine : Starting Servlet engine: [Apache Tomcat/9.0.37]
2020-08-19 01:37:24.810 INFO 34364 --- [ restartedMain] o.a.c.c.C.[Tomcat].[localhost].[/] : Initializing Spring embedded WebApplicationContext
2020-08-19 01:37:24.810 INFO 34364 --- [ restartedMain] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 722 ms
2020-08-19 01:37:24.849 INFO 34364 --- [ restartedMain] f.a.AutowiredAnnotationBeanPostProcessor : Autowired annotation is not supported on static fields: static com.emerald.paymentengine.DataSourceDbConfig com.emerald.paymentengine.ApplicationRun.dbConfig
Connection established !!
2020-08-19 01:37:24.981 INFO 34364 --- [ restartedMain] o.s.s.concurrent.ThreadPoolTaskExecutor : Initializing ExecutorService 'applicationTaskExecutor'
2020-08-19 01:37:25.116 INFO 34364 --- [ restartedMain] o.s.b.d.a.OptionalLiveReloadServer : LiveReload server is running on port 35729
2020-08-19 01:37:25.140 INFO 34364 --- [ restartedMain] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8082 (http) with context path ''
2020-08-19 01:37:25.148 INFO 34364 --- [ restartedMain] c.emerald.paymentengine.ApplicationRun : Started ApplicationRun in 1.335 seconds (JVM running for 2.406)
我当时认为@SpringBootApplication将自动扫描主包和子包，并能够选择所需的bean。如第一种情况所述，如何通过将Config.java文件放在不同的包中来使其工作？
代码：
ApplicationRun.java
package com.emerald.paymentengine;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class ApplicationRun {
@Autowired
static
DataSourceDbConfig dbConfig;
public ApplicationRun(DataSourceDbConfig dbConfig){
ApplicationRun.dbConfig = dbConfig ;
}
public static void main(String[] args) {
SpringApplication.run(ApplicationRun.class,args);
dbConfig.dataSource();
}
}
DataSourceDbConfig.java
package com.emerlad.paymentengine.config;;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;
import oracle.jdbc.pool.OracleDataSource;
import java.sql.SQLException;
import javax.sql.DataSource;
@Component
@Configuration
@ConfigurationProperties("spring.datasource")
public class DataSourceDbConfig {
@Value("${spring.datasource.url}")
private String dbUrl;
@Value("${spring.datasource.username}")
private String dbUser;
@Value("${spring.datasource.secure}")
private String dbPasswrd;
@Bean
public DataSource dataSource() {
OracleDataSource dataSource = null;
try {
dataSource = new OracleDataSource();
dataSource.setUser(dbUser);
dataSource.setPassword(dbPasswrd);
dataSource.setURL(dbUrl);
System.out.println("Connection established !!");
} catch (SQLException e) {
System.out.println("An issue occured while establishing connection !!");
e.printStackTrace();
}
return dataSource;
}
}
解决方法
老实说，我不明白您要完成什么，但这是如何在您的主要方法中获取DataSource bean的方法：
ApplicationRun.java：
package com.emerald.paymentengine;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import com.emerlad.paymentengine.config.DataSourceDbConfig;
import org.springframework.context.annotation.Import;
import javax.sql.DataSource;
@SpringBootApplication
@Import(DataSourceDbConfig.class)
public class ApplicationRun {
public static void main(String[] args) {
ApplicationContext context = SpringApplication.run(ApplicationRun.class,args);
DataSource dataSource = context.getBean(DataSource.class)
}
}
DataSourceDbConfig.java：
package com.emerlad.paymentengine.config;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.stereotype.Component;
import oracle.jdbc.pool.OracleDataSource;
import java.sql.SQLException;
import javax.sql.DataSource;
@Configuration
@ConfigurationProperties("spring.datasource")
public class DataSourceDbConfig {
@Value("${spring.datasource.url}")
private String dbUrl;
@Value("${spring.datasource.username}")
private String dbUser;
@Value("${spring.datasource.secure}")
private String dbPasswrd;
@Bean
public DataSource dataSource() {
OracleDataSource dataSource = null;
try {
dataSource = new OracleDataSource();
dataSource.setUser(dbUser);
dataSource.setPassword(dbPasswrd);
dataSource.setURL(dbUrl);
System.out.println("Connection established !!");
} catch (SQLException e) {
System.out.println("An issue occured while establishing connection !!");
e.printStackTrace();
}
return dataSource;
}
}
- 类
DataSourceDbConfig-使用@Configuration包含@Component，因此您可以摆脱它 - 类
ApplicationRun-我将使其保持简单并删除DataSourceDbConfig
@SpringBootApplication
public class ApplicationRun {
public static void main(String[] args) {
ApplicationContext appContext = SpringApplication.run(ApplicationRun.class,args);
// Getting datasource from application context.
DataSource dataSource = appContext.getBean(DataSource.class);
}
}
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