Java jaxb从xml解码到java对象返回空值

Question

你好，我是 Jaxb 的新手，已经花了 3 个多小时用这个解码的东西搜索这个 NullPointerException ，但没有发现任何对我有用的东西。我尝试使用 inputStream、StringReader 和 Buffered reader，但是当我尝试将 XML 文件解码为 java 对象时，所有结果都为空值，这是一个异常(exception):

java.lang.IllegalStateException:无法执行 CommandLineRunner 在 org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:784) ~[spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE] 在 org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:765) ~[spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE] 在 org.springframework.boot.SpringApplication.run(SpringApplication.java:319) ~[spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE] 在 org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) ~[spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE] 在 org.springframework.boot.SpringApplication.run(SpringApplication.java:1204) ~[spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE] 在 kso.xmlprocessing.XmlprocessingApplication.main(XmlprocessingApplication.java:10) ~[classes/:na] 在 java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0( native 方法) ~[na:na] 在 java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na] 在 java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na] 在 java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na] 在 org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) ~[spring-boot-devtools-2.1.8.RELEASE.jar:2.1.8.RELEASE]引起原因:java.lang.NullPointerException:null 在 kso.xmlprocessing.service.SupplierServiceImpl.seedSuppliers(SupplierServiceImpl.java:38) ~[classes/:na] 在 kso.xmlprocessing.web.controller.CarDealerController.run(CarDealerController.java:17) ~[classes/:na] 在 org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:781) ~[spring-boot-2.1.8.RELEASE.jar:2.1.8.RELEASE] ...省略10个常见框架

我有这些类(class):

@XmlRootElement(name = "supplier")
@XmlAccessorType(XmlAccessType.FIELD)
public class SupplierDto {
@XmlAttribute
private String name;
@XmlAttribute(name = "is-importer")
private Boolean isImporter;

public SupplierDto() {
}

public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public Boolean getImporter() {
    return isImporter;
}

public void setImporter(Boolean importer) {
    isImporter = importer;
}

}

@XmlRootElement(name = "suppliers")
@XmlAccessorType(XmlAccessType.FIELD)
public class SupplierRootDto {

@XmlElement
private List<SupplierDto> supplierDtos;

public SupplierRootDto() {
}

public List<SupplierDto> getSupplierDtos() {
    return supplierDtos;
}

public void setSupplierDtos(List<SupplierDto> supplierDtos) {
    this.supplierDtos = supplierDtos;
}

}

这是我解析数据的逻辑:

JAXBContext context = JAXBContext.newInstance(SupplierRootDto.class);
    Unmarshaller unmarshaller = context.createUnmarshaller();

    String path = "suppliers.xml";
    BufferedReader reader = new BufferedReader(new FileReader(new 
File(path)));

    SupplierRootDto list = (SupplierRootDto) 
unmarshaller.unmarshal(reader);

    for (SupplierDto supplierDto : list.getSupplierDtos()) {

this.supplierRepository.saveAndFlush(this.modelMapper.map(supplierDto, 
Supplier.class));
    }

这是 XML 文件:

<?xml version="1.0" encoding="utf-8"?>
 <suppliers>
 <supplier name="3M Company" is-importer="true"/>
 <supplier name="Agway Inc." is-importer="false"/>
 <supplier name="Anthem, Inc." is-importer="true"/>
 <supplier name="Airgas, Inc." is-importer="false"/>
 <supplier name="Big Lots, Inc." is-importer="true"/>
 <supplier name="Caterpillar Inc." is-importer="false"/>
 <supplier name="Casey's General Stores Inc." is-importer="true"/>
 <supplier name="Cintas Corp." is-importer="false"/>
 <supplier name="Chubb Corp" is-importer="true"/>
 <supplier name="Cintas Corp." is-importer="false"/>
 <supplier name="CNF Inc." is-importer="true"/>
 <supplier name="CMGI Inc." is-importer="true"/>
 <supplier name="The Clorox Co." is-importer="false"/>
 <supplier name="Danaher Corporation" is-importer="true"/>
 <supplier name="E.I. Du Pont de Nemours and Company" is- 
 importer="false"/>
 <supplier name="E*Trade Group, Inc." is-importer="true"/>
 <supplier name="Emcor Group Inc." is-importer="true"/>
 <supplier name="GenCorp Inc." is-importer="false"/>
 <supplier name="IDT Corporation" is-importer="true"/>
 <supplier name="Level 3 Communications Inc." is-importer="false"/>
 <supplier name="Merck &amp; Co., Inc." is-importer="true"/>
 <supplier name="Nicor Inc" is-importer="false"/>
 <supplier name="Olin Corp." is-importer="true"/>
 <supplier name="Paychex Inc" is-importer="true"/>
 <supplier name="Saks Inc" is-importer="false"/>
 <supplier name="Sunoco Inc." is-importer="true"/>
 <supplier name="Textron Inc" is-importer="true"/>
 <supplier name="VF Corporation" is-importer="false"/>
 <supplier name="Wyeth" is-importer="true"/>
 <supplier name="Zale" is-importer="false"/>
</suppliers>

Answer 1

问题是您的 POJOS + 注释未正确映射到提供的 xml。具体来说，在“SupplierRootDto”字段中“supplierDtos”需要更改或使用注释来覆盖，如下所示:

@XmlRootElement(name = "suppliers")
@XmlAccessorType(XmlAccessType.FIELD)
public class SupplierRootDto {

    // ADD NAME TO MATCH THE XML ELEMENT
    @XmlElement(name = "supplier")
    private List<SupplierDto> supplierDtos;

    public SupplierRootDto() {
    }

    public List<SupplierDto> getSupplierDtos() {
        return supplierDtos;
    }

    public void setSupplierDtos(List<SupplierDto> supplierDtos) {
        this.supplierDtos = supplierDtos;
    }
}

然后它将正确解码。