我正在使用现有实体和存储库创建Spring批处理项目。我需要使用自定义ItemReader
作为使用现有jpa存储库读取数据的作业。
自定义阅读器
public class InMemoryReader implements ItemReader<Product> {
@Autowired
private ProductService productService;
private int nextStudentIndex;
private List<Product> studentData;
public InMemoryReader() {
initialize();
}
private void initialize() {
studentData = new ArrayList<Product>();
studentData.add(new Product("hi"));
for (Product p : productService.get())
studentData.add(p);
nextStudentIndex = 0;
}
@Override
public Product read() throws Exception {
Product nextStudent = null;
if (nextStudentIndex < studentData.size()) {
nextStudent = studentData.get(nextStudentIndex);
nextStudentIndex++;
}
return nextStudent;
}
}
但我无法在ProductService
中自动加itemreader
。它抛出错误如下:
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'reader' defined in class path resource [wariyum/sb/emailNotifier/BatchConfiguration.class]: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.batch.item.ItemReader]: Factory method 'reader' threw exception; nested exception is java.lang.NullPointerException
at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:599)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1123)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1018)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:510)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:305)
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:301)
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:196)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772)
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:834)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:537)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:689)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:321)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:969)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:958)
at wariyum.sb.emailNotifier.Application.main(Application.java:15)
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.springframework.batch.item.ItemReader]: Factory method 'reader' threw exception; nested exception is java.lang.NullPointerException
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:189)
at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:588)
... 16 common frames omitted
Caused by: java.lang.NullPointerException: null
at wariyum.sb.emailNotifier.service.InMemoryReader.initialize(InMemoryReader.java:31)
at wariyum.sb.emailNotifier.service.InMemoryReader.<init>(InMemoryReader.java:24)
at wariyum.sb.emailNotifier.BatchConfiguration.reader(BatchConfiguration.java:41)
at wariyum.sb.emailNotifier.BatchConfiguration$$EnhancerBySpringCGLIB$$df186b4e.CGLIB$reader$0(<generated>)
at wariyum.sb.emailNotifier.BatchConfiguration$$EnhancerBySpringCGLIB$$df186b4e$$FastClassBySpringCGLIB$$724d6a16.invoke(<generated>)
at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:228)
at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:318)
at wariyum.sb.emailNotifier.BatchConfiguration$$EnhancerBySpringCGLIB$$df186b4e.reader(<generated>)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:162)
... 17 common frames omitted
批量配置文件
@Configuration
@EnableBatchProcessing
public class BatchConfiguration {
@Autowired
public JobBuilderFactory jobBuilderFactory;
@Autowired
private DataSource dataSource;
@Autowired
public StepBuilderFactory stepBuilderFactory;
@Bean
public ItemReader<Product> reader() throws Exception {
return new InMemoryReader();
}
@Bean
public ProductItemProcessor processor() {
return new ProductItemProcessor();
}
@Bean
public ItemWriter<Product> writer() {
return new ItemWriter<Product>() {
@Override
public void write(List<? extends Product> items) throws Exception {
}
};
}
// end::readerwriterprocessor[]
// tag::listener[]
@Bean
public JobExecutionListener listener() {
return null;
}
// end::listener[]
// tag::jobstep[]
@Bean
public Job importPerson(JobBuilderFactory jobs, Step s1) {
return jobs.get("import")
.incrementer(new RunIdIncrementer()) // because a spring config bug, this incrementer is not really useful
.flow(s1)
.end()
.build();
}
@Bean
public Step step1() throws Exception {
return stepBuilderFactory.get("step1")
.<Product, Product>chunk(10)
.reader(reader())
.processor(processor())
.writer(writer())
.build();
}
}
产品服务实施
@Service("productService")
public class ProductServiceImpl implements ProductService {
private ProductRepository repository;
@Autowired
public ProductServiceImpl(ProductRepository repository) {
this.repository = repository;
}
@Override
public List<Product> get() {
List<Product> list = new ArrayList<Product>();
for (Product p : repository.findAll())
list.add(p);
return list;
}
}
答案 0 :(得分:6)
您正在从构造函数调用initialize()
,即在连接ProductService
依赖项之前。
从构造函数中删除对initialize()
的调用,然后让Spring通过使用@PostConstruct
或使用此处概述的其他方法之一来连接依赖项之后调用它: