java - 在 XmlAdapter 中获取当前主机

Question

有没有办法在 XmlAdapter 中检索当前的基本 URI？或者这通常是如何实现的？

public class Service{
...
    @GET
    public MyEntity getEntity() {
        return em.find(MyEntity.class, "dummy");
    }
...
}


@XmlRootElement(name = "myEntity")
public class MyEntity {

    @XmlJavaTypeAdapter(MyAdapter.class)
    private Entity2 entity2Ref;
...

}



public class MyAdapter extends XmlAdapter<Entity2Ref, Entity2> {

// Is NULL but shold be injected with host URI
@Context
UriInfo uri;

...

}

Answer 1

下面是如何完成此操作的完整示例:

XML 响应

下面我将演示如何获取以下响应，其中 address 元素中的 URI 通过识别 的 XmlAdapter 放入UriInfo.

<?xml version="1.0" encoding="UTF-8"?>
<customer id="1">
    <name>Jane Doe</name>
    <address>http://localhost:9999/address/123</address>
</customer>

Java 模型

下面是我将用于此示例的 Java 模型。

客户

默认情况下，Address 类的内容将编码在 customer 元素下。我们将使用 XmlAdapter 对此执行特殊处理。

import javax.xml.bind.annotation.*;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

@XmlRootElement
@XmlType(propOrder={"name", "address"})
public class Customer {

    private int id;
    private String name;
    private Address address;

    @XmlAttribute
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    @XmlJavaTypeAdapter(AddressAdapter.class)
    public Address getAddress() {
        return address;
    }

    public void setAddress(Address address) {
        this.address = address;
    }

}

地址

import javax.xml.bind.annotation.XmlAttribute;

public class Address {

    private int id;

    @XmlAttribute
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

}

Xml适配器

下面是我们将使用的XmlAdapter。请注意它如何从 AddressResource 获取信息以构建 URI。它需要一个 UriInfo，这使其成为有状态的。我们需要在 Marshaller 上设置此 XmlAdapter 的实例，以使一切正常工作。

import javax.ws.rs.core.*;
import javax.xml.bind.annotation.adapters.XmlAdapter;

public class AddressAdapter extends XmlAdapter<String, Address> {

    private UriInfo uriInfo;

    public AddressAdapter() {
    }

    public AddressAdapter(UriInfo uriInfo) {
        this.uriInfo = uriInfo;
    }

    @Override
    public Address unmarshal(String v) throws Exception {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public String marshal(Address v) throws Exception {
        if(null == uriInfo) {
            return "";
        }
        UriBuilder builder = UriBuilder.fromResource(AddressResource.class);
        System.out.println(uriInfo.getAbsolutePath().getHost());
        builder.scheme(uriInfo.getAbsolutePath().getScheme());
        builder.host(uriInfo.getAbsolutePath().getHost());
        builder.port(uriInfo.getAbsolutePath().getPort());
        builder.path(AddressResource.class, "get");
        return builder.build(v.getId()).toString();
    }

}

JAX-RS 服务

在此示例中，有两个服务，一个用于 Address，另一个用于 Customer。

地址资源

import javax.ws.rs.*;
import javax.ws.rs.ext.Provider;

@Provider
@Path("/address")
public class AddressResource {

    @GET
    @Path("{id}")
    public Address get(@PathParam("id") int id) {
        Address address = new Address();
        address.setId(id);
        return address;
    }

}

客户资源

由于我们有一个有状态的 XmlAdapter，因此我们不能仅通过默认绑定(bind)来利用 JAXB。相反，我们可以通过 StreamingOutput 访问 JAXB。

import javax.ws.rs.*;
import javax.ws.rs.core.*;
import javax.ws.rs.ext.Provider;
import javax.xml.bind.*;

@Provider
@Path("/customer")
public class CustomerResource {

    private JAXBContext jaxbContext;

    public CustomerResource() {
        try {
            jaxbContext = JAXBContext.newInstance(Customer.class);
        } catch (JAXBException e) {
            // TODO - Handle Exception
        }
    }

    @GET
    @Path("{id}")
    @Produces(MediaType.APPLICATION_XML)
    public StreamingOutput get(@Context UriInfo uriInfo, @PathParam("id") int id) {
        Customer customer = new Customer();
        customer.setId(id);
        customer.setName("Jane Doe");

        Address address = new Address();
        address.setId(123);
        customer.setAddress(address);

        return new MyStreamingOutput(jaxbContext, customer, uriInfo);
    }

}

流输出

import java.io.*;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.*;
import javax.xml.bind.*;

public class MyStreamingOutput implements StreamingOutput {

    private JAXBContext jaxbContext;
    private Object object;
    private UriInfo uriInfo;

    public MyStreamingOutput(JAXBContext jc, Object object, UriInfo uriInfo) {
        this.jaxbContext = jc;
        this.object = object;
        this.uriInfo = uriInfo;
    }

    @Override
    public void write(OutputStream os) throws IOException,
            WebApplicationException {
        try {
            Marshaller marshaller = jaxbContext.createMarshaller();
            marshaller.setAdapter(new AddressAdapter(uriInfo));
            marshaller.marshal(object, os);
        } catch(JAXBException jaxbException) {
            throw new WebApplicationException(jaxbException);
        }
    }

}