如何将 marshaller 对象写入 httpresponse 对象并将其下载为 xml 文件

Question

我正在尝试使用 JaxB 从我的数据 class 创建一个 xml 文件并下载它。

我已经从 java 对象创建了 marshaller 对象。但是我无法 return 这个对象作为 xml 文件。当我点击该方法时，我得到一个空的 xml 文件已下载。我是File IO编码的新手，请在这方面帮助我。

以下是我的控制器方法

import java.io.FileOutputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.validation.constraints.NotNull;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;

import org.apache.commons.collections.CollectionUtils;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@Controller
public class MyController{

@RequestMapping(value = PRODUCT_CODE_PATH_VARIABLE_PATTERN, method = RequestMethod.GET)
public void downloadProduct(@PathVariable("productCode") @NotNull final String productCode, final HttpServletRequest request, final HttpServletResponse response) throws Exception
    {
        response.setContentType("application/xml");
        response.setHeader("Content-Disposition", "attachment; filename=" + productCode + ".xml");
        final ProductDataJaxb productDataJaxb = getProductJaxObj(productCode);
        final JAXBContext jaxbContext = JAXBContext.newInstance(ProductDataJaxb.class);
        final Marshaller marshaller = jaxbContext.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
        final OutputStream outputStream = new FileOutputStream(productCode + ".xml");
        marshaller.marshal(productDataJaxb, outputStream);

    }
}

我的数据 class 其 xml 表示是我在下载的 xml 文件中想要的。

import java.util.List;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;


@XmlRootElement(name = "Product")
@XmlType(propOrder ={ "code", "categories", "description" })
public class ProductDataJaxb
{

    private String code;
    private String description;
    private List<String> categories;

    /**
     * @return the code
     */
    @XmlElement
    public String getCode()
    {
        return code;
    }

    /**
     * @param code
     *           the code to set
     */
    public void setCode(final String code)
    {
        this.code = code;
    }

    /**
     * @return the description
     */
    @XmlElement
    public String getDescription()
    {
        return description;
    }

    /**
     * @param description
     *           the description to set
     */
    public void setDescription(final String description)
    {
        this.description = description;
    }

    /**
     * @return the categories
     */
    @XmlElement
    public List<String> getCategories()
    {
        return categories;
    }

    /**
     * @param categories
     *           the categories to set
     */
    public void setCategories(final List<String> categories)
    {
        this.categories = categories;
    }

  }

Answer 1

在您的 downloadProduct 方法中，您应该 add/change/remove 一些事情：

将 return-type 更改为 ProductDataJaxb
添加@ResponseBody注解表示return-value 应该进入 HTTP 响应
在@RequestMapping注解中指定输出media-type"application/xml"以指示在HTTP响应

Content-Type

删除所有 JAXB 编组内容，因为 Spring 会为您完成。
您不再需要 HttpServletRequest 和 HttpServletResponse 方法参数

您的方法将如下所示：

@RequestMapping(value = PRODUCT_CODE_PATH_VARIABLE_PATTERN,
        method = RequestMethod.GET,
        produces = "application/xml")
@ResponseBody
public ProductDataJaxb downloadProduct(@PathVariable("productCode") @NotNull final String productCode) throws Exception
{
    final ProductDataJaxb productDataJaxb = getProductJaxObj(productCode);
    return productDataJaxb;
}

Answer 2

经过反复试验，我得到了如下解决方案来实现我的要求。

@RequestMapping(value = PRODUCT_CODE_PATH_VARIABLE_PATTERN, method = RequestMethod.GET)
public void downloadProduct(@PathVariable("productCode") @NotNull final String productCode, final HttpServletRequest request,
        final HttpServletResponse response) throws Exception
{
    response.setContentType("application/xml");
    response.setHeader("Content-Disposition", "attachment; filename=" + productCode + ".xml");
    final ProductDataJaxb productDataJaxb = getProductJaxObj(productCode);
    final JAXBContext jaxbContext = JAXBContext.newInstance(ProductDataJaxb.class);
    final Marshaller marshaller = jaxbContext.createMarshaller();
    marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
    marshaller.marshal(productDataJaxb, response.getOutputStream());

}

我只需将 HttpResponse 对象的输出 Stream 对象传递给 marshal 方法即可完成此操作。天哪！我现在真的需要学习 IO 概念.... :)

如何将 marshaller 对象写入 httpresponse 对象并将其下载为 xml 文件

how to write marshaller object to httpresponse object and download it as xml file

spring-mvc

jaxb

marshalling