java - 构造函数的参数 0 需要一个类型为 'java.lang.String' 的 bean，但找不到

Question

我正在使用 spring boot 2.X 应用程序开发 spring batch，实际上它的现有代码是我从 git 中 check out 的。运行应用程序时，由于以下错误仅对我失败，而相同的代码对其他人也有效。

s.c.a.AnnotationConfigApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'inputItemReader' defined in file [C:\Users\XYZ\git\main\batch\CBatchProcessing\target\classes\com\main\batchprocessing\batch\reader\InputItemReader.class]: Unsatisfied dependency expressed through **constructor parameter 0; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'java.lang.String' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations**: {}


Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2018-10-16 23:23:37.411 ERROR 2384 --- [           main] o.s.b.d.LoggingFailureAnalysisReporter   : 

***************************
APPLICATION FAILED TO START
***************************

Description:

**Parameter 0 of constructor in com.main.batchprocessing.batch.reader.InputItemReader required a bean of type 'java.lang.String' that could not be found.**


Action:

Consider defining a bean of type 'java.lang.String' in your configuration.

我已经检查了下面

1. 所有 Spring 组件都正确地使用了@Component、@Service、@Controller、@Repository 等注释...
2. 还提供了@ComponentScan 和@EnableAutoCOnfiguration。
3. 尝试在声明中给出“java.lang.String”。

代码:

    import java.util.Map;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.batch.core.ExitStatus;
    import org.springframework.batch.core.StepExecution;
    import org.springframework.batch.core.StepExecutionListener;
    import org.springframework.batch.item.file.FlatFileItemReader;
    import org.springframework.batch.item.file.mapping.JsonLineMapper;
    import 
    org.springframework.batch.item.file.separator.JsonRecordSeparatorPolicy;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.context.annotation.Bean;
    import org.springframework.core.io.FileSystemResource;
    import org.springframework.stereotype.Component;

    @Component
    public class InputItemReader extends  FlatFileItemReader<Map<String, 
     Object>> implements StepExecutionListener {

    @Autowired
    private InputFileHeaderValidator inputFileHeaderValidator; 

    @Autowired
    private FileAuditService fileAuditService;

    private final Logger log = 
    LoggerFactory.getLogger(InputItemReader.class);

    private java.lang.String inputFilePath;

    public InputItemReader(String inputFilePath) {
        setLineMapper(new JsonLineMapper());
        setRecordSeparatorPolicy(new JsonRecordSeparatorPolicy());
        setResource(new FileSystemResource(inputFilePath));
        this.inputFilePath = inputFilePath;
    }
   }

Answer 1

由于您没有提供公共(public)默认构造函数并且您添加了自己的非默认构造函数，因此实例化将失败。我建议您将输入文件路径定义为 @Value("${inputFilePath}") 之类的属性。如果您需要在 bean 中进一步初始化，请定义一个 void 方法并使用 @PostConstruct 对其进行注释，然后在其中进行初始化。