读取Java中的xml文件-仅选定元素

Question

I have just started to learn how to make a java object from a XML. However, now I have a tricky input and I don't really know how to solve it.

This is the input:

<?xml version="1.0" encoding="UTF-8"?>
<return>
  <productChange cd_product="711" ds_product="MBL40337 I151 BLACK P" cd_species="UN" cd_tipi="61062000" cd_cst="5" qt_weight="" cd_nbm="" dt="2016-05-04 11:47:36">
    <productvalue cd_company="1" cd_product="711" tp_value="P" cd_value="1" vl_product="61.39">
      <tipovaluePrd tp_value="P" cd_value="1" ds_value="SALE" cd_corrency="1" />
    </productvalue>
    <productvalue cd_company="1" cd_product="711" tp_value="P" cd_value="4" vl_product="129.8">
      <tipovaluePrd tp_value="P" cd_value="4" ds_value="SALE STORE" cd_corrency="1" />
    </productvalue>
    <productvalue cd_company="1" cd_product="711" tp_value="P" cd_value="5" vl_product="64.9">
      <tipovaluePrd tp_value="P" cd_value="5" ds_value="SALE AT" cd_corrency="1" />
    </productvalue>
    <productvalue cd_company="1" cd_product="711" tp_value="P" cd_value="8" vl_product="122.78">
      <tipovaluePrd tp_value="P" cd_value="8" ds_value="SALE FQ" cd_corrency="1" />
    </productvalue>
  </productChange>
</return>

To consume this xml with JaxB (XML provided by a third party company) I have built the following classes:

@XmlAccessorType(XmlAccessType.FIELD)
public class ProductUpdateResponse {

  @XmlAttribute(name = "cd_product")
  private Integer productCode;
  @XmlAttribute(name = "ds_product")
  private String productDescription;
  @XmlAttribute(name = "cd_species")
  private String productSpecie;
  @XmlAttribute(name = "cd_tipi")
  private Integer productTIPI;
  @XmlAttribute(name = "cd_cst")
  private Integer productCST;
  @XmlAttribute(name = "qt_weight")
  private String productWeight;
  @XmlAttribute(name = "cd_nbm")
  private String productNBM;
  @XmlAttribute(name = "dt")
  private String productDate;

  @XmlElement(name = "productvalue")
  private ProductValueType productValue;
// getters and setters
}

@XmlAccessorType(XmlAccessType.FIELD)
public class ProductValue {
  @XmlAttribute(name = "cd_product")
  private Integer productCode;
  @XmlAttribute(name = "cd_company")
  private Integer companyCode;
  @XmlAttribute(name = "tp_value")
  private String valueType;
  @XmlAttribute(name = "cd_value")
  private Integer valueCode;
  @XmlAttribute(name = "vl_product")
  private BigDecimal productValue;

  @XmlElement(name = "tipovaluePrd")
  private ProductValueType productValueType;
//getters and seters
}

@XmlAccessorType(XmlAccessType.FIELD)
public class ProductValueType {
  @XmlAttribute(name = "tp_value")
  private String valueType;
  @XmlAttribute(name = "cd_value")
  private String valueCode;
  @XmlAttribute(name = "ds_value")
  private String valueDescription;
  @XmlAttribute(name = "cd_corrency")
  private Integer valueCurrency;
//getters and seters
}

However, the main information, for me, is comming as null (productvalue) I wonder if it is because there are four tags productvalue in the xml (I just need the one whose tipovaluePrd.cd_value is 4 ).

Below is the method I'm using to parse the XML:

private ProductUpdateResponse buildResponse(String rawResponse, Class<T> responseClass) {

    JAXBContext jaxbContext = null;
    try {
      jaxbContext = JAXBContext.newInstance(responseClass);
      Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
      StringReader reader = new StringReader(rawResponse);
      return (ProductUpdateResponse) unmarshaller.unmarshal(reader);
    } catch (JAXBException | ClassCastException e) {
      return null;
    }
  }

So, I wonder if there is a way to read specifically the value I want ( productvalue element that has tipovaluePrd.cd_value = 4 ) and how could I do that. If there isn't, how should I build my class so I can read properly everything?

Changing the input is not an option here...

Thanks in advance for any help.

Answer 1

I'm actually surprised you're getting a result from JAXB with your current setup.

You lack a class representing your root element :

@XmlRootElement(name="return")
@XmlAccessorType(XmlAccessType.FIELD)
public class Return {
     @XmlElement(name="productchange")
     private ProductUpdateResponse response;

     //getters and setters
}

Also, in your ProductUpdateResponse class, you should change :

@XmlElement(name = "productvalue")
private ProductValueType productValue;

by

@XmlElement(name = "productvalue")
private List<ProductValue> productValues;

Finally, in your buildResponse method, make sure the responseClass argument is Return.class.

With this, you should have a list with all your productvalue element. You just have to get the productvalue your interested in from it.

If you only want to get the element you're interested with :

1. As swasa suggested it, you can use the javax.xml.xpath to make an Xpath request on your XML.

2. If you're willing to change your JAXB Implementation : EclipseLink JAXB Implementation implements an @XmlPath annotation that allows you to bind objects according to an XPath request :

    @XmlPath(name = "productvalue/tipovaluePrd[@cd_value=4]") \nprivate ProductValueType productValueType;