我目前正在尝试创建一个 InjectableProvider与 Jersey ，但我无法让 Jersey 拿起它。

除了使用 @Provider 之外，我找不到任何有关其用法的真实示例，甚至找不到如何使用它的方法。关于实现的注释。似乎在 Jersey 写它的人在一些帖子中暗示这足以让它被接受。

我是否需要指定一些 SPI 服务文件，或者将其添加到某个工厂的某个地方？

注意:我在 Glassfish 3.1 中运行，并使用 Spring 3.1。 Spring 可能会以某种方式接管 Provider 的自动加载，这似乎是合理的。 s。不过，我就是不知道。我没有使用 Spring 来管理下面建议的 InjectableProvider，也没有尝试以其他方式添加它，这可能是我的问题。

import com.sun.jersey.core.spi.component.ComponentContext;
import com.sun.jersey.spi.inject.Injectable;
import com.sun.jersey.spi.inject.PerRequestTypeInjectableProvider;

public abstract class AbstractAttributeInjectableProvider<T>
        extends PerRequestTypeInjectableProvider<AttributeParam, T>
{
    protected final Class<T> type;

    public AbstractAttributeInjectableProvider(Class<T> type)
    {
        super(type);

        this.type = type;
    }

    @Override
    public Injectable<T> getInjectable(ComponentContext componentContext,
                                       AttributeParam attributeParam)
    {
        return new AttributeInjectable<T>(type, attributeParam.value());
    }
}

import javax.ws.rs.ext.Provider;

@Component // <- Spring Annotation
@Provider  // <- Jersey Annotation
public class MyTypeAttributeInjectableProvider
        extends AbstractAttributeInjectableProvider<MyType>
{
    public MyTypeAttributeInjectableProvider()
    {
        super(MyType.class);
    }
}

@Target({ElementType.FIELD, ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface AttributeParam
{
    /**
     * The value is the name to request as an attribute from an {@link
     * HttpContext}'s {@link HttpServletRequest}.
     * @return Never {@code null}. Should never be blank.
     */
    String value();
}

public class AttributeInjectable<T> implements Injectable<T>
{
    /**
     * The type of data that is being requested.
     */
    private final Class<T> type;
    /**
     * The name to extract from the {@link HttpServletRequest} attributes.
     */
    private final String name;

    /**
     * Converts the attribute with the given {@code name} into the {@code type}.
     * @param type The type of data being retrieved
     * @param name The name being retrieved.
     * @throws IllegalArgumentException if any parameter is {@code null}.
     */
    public AttributeInjectable(Class<T> type, String name)
    {
        // check for null

        // required
        this.type = type;
        this.name = name;
    }

    /**
     * Look up the requested value.
     * @return {@code null} if the attribute does not exist or if it is not the
     *         appropriate {@link Class type}.
     *         <p />
     *         Note: Jersey most likely will fail if the value is {@code null}.
     * @throws NullPointerException if {@link HttpServletRequest} is unset.
     * @see #getRequest()
     */
    @Override
    public T getValue()
    {
        T value = null;
        Object object = getRequest().getAttribute(name);

        if (type.isInstance(object))
        {
            value = type.cast(object);
        }

        return value;
    }

    /**
     * Get the current {@link HttpServletRequest} [hopefully] being made
     * containing the {@link HttpServletRequest#getAttribute(String) attribute}.
     * @throws NullPointerException if the Servlet Filter for the {@link
     *                              RequestContextHolder} is not setup
     *                              appropriately.
     * @see org.springframework.web.filter.RequestContextFilter
     */
    protected HttpServletRequest getRequest()
    {
        // get the request from the Spring Context Holder (this is done for
        //  every request by a filter)
        ServletRequestAttributes attributes =
            (ServletRequestAttributes)RequestContextHolder.getRequestAttributes();

        return attributes.getRequest();
    }
}

<filter>
    <filter-name>requestContextFilter</filter-name>
    <filter-class>
        org.springframework.web.filter.RequestContextFilter
    </filter-class>
</filter>
<filter-mapping>
    <filter-name>requestContextFilter</filter-name>
    <url-pattern>/path/that/i/wanted/*</url-pattern>
</filter-mapping>

@Path("my/path/to")
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.TEXT_PLAIN)
public interface MyService
{
    @Path("service1")
    @POST
    Response postData(@AttributeParam("some.name") MyType data);

    @Path("service2")
    @POST
    Response postOtherData(@AttributeParam("other.name") MyOtherType data);
}

@Component // Spring
public class MyServiceBean implements MyService
{
    @Override
    public Response postData(MyType data)
    {
        // interact with data
    }

    @Override
    public Response postOtherData(MyOtherType data)
    {
        // interact with data
    }
}

public class RequestContextBean
{
    /**
     * The current request from the user.
     */
    @Context
    protected HttpServletRequest request;

    /**
     * Get the attribute associated with the current {@link HttpServletRequest}.
     * @param name The attribute name.
     * @param type The expected type of the attribute.
     * @return {@code null} if the attribute does not exist, or if it does not
     *         match the {@code type}. Otherwise the appropriately casted
     *         attribute.
     * @throws NullPointerException if {@code type} is {@code null}.
     */
    public <T> T getAttribute(String name, Class<T> type)
    {
        T value = null;
        Object attribute = request.getAttribute(name);

        if (type.isInstance(attribute))
        {
            value = type.cast(attribute);
        }

        return value;
    }
}

@Path("my/path/to")
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.TEXT_PLAIN)
public interface MyService
{
    @Path("service1")
    @POST
    Response postData();

    @Path("service2")
    @POST
    Response postOtherData();
}

@Component
public class MyServiceBean extends RequestContextBean implements MyService
{
    @Override
    public Response postData()
    {
        MyType data = getAttribute("some.name", MyType.class);
        // interact with data
    }

    @Override
    Response postOtherData()
    {
        MyOtherType data = getAttribute("other.name", MyOtherType.class);
        // interact with data
    }
}

@Component
@Provider
public class AttributeParamInjectableProvider
        implements InjectableProvider<AttributeParam, Type>
{
    /**
     * {@inheritDoc}
     * @return Always {@link ComponentScope#PerRequest}.
     */
    @Override
    public ComponentScope getScope()
    {
        return ComponentScope.PerRequest;
    }

    /**
     * Get an {@link AttributeInjectable} to inject the {@code parameter} for
     * the given {@code type}.
     * @param context Unused.
     * @param parameter The requested parameter
     * @param type The type of data to be returned.
     * @return {@code null} if {@code type} is not a {@link Class}. Otherwise
     *         an {@link AttributeInjectable}.
     */
    @Override
    public AttributeInjectable<?> getInjectable(ComponentContext context,
                                                AttributeParam parameter,
                                                Type type)
    {
        AttributeInjectable<?> injectable = null;

        // as long as it's something that we can work with...
        if (type instanceof Class)
        {
            injectable = getInjectable((Class<?>)type, parameter);
        }

        return injectable;
    }

    /**
     * Create a new {@link AttributeInjectable} for the given {@code type} and
     * {@code parameter}.
     * <p />
     * This is provided to avoid the support for generics without the need for
     * {@code SuppressWarnings} (avoided via indirection).
     * @param type The type of data to be returned.
     * @param parameter The requested parameter
     * @param <T> The type of data being accessed by the {@code param}.
     * @return Never {@code null}.
     */
    protected <T> AttributeInjectable<T> getInjectable(Class<T> type,
                                                       AttributeParam parameter)
    {
        return new AttributeInjectable<T>(type, parameter.value());
    }
}

最佳答案

你是如何初始化 Jersey 的？

我将假设您使用 Jersey 使用 jersey-spring servlet。在这种情况下， Jersey 将默认使用 Spring bean 进行初始化，因此您的 Provider必须是一个Spring bean。尝试添加 @Named (或者如果您不使用 atinject @Component 或 Spring 注释之一)到您的 Provider .

An example of using Injectable Providers .

更新 :注入(inject)范围更清晰:
Provider必须是一个单例，因为对于所有实际目的来说，它是一个与范围相关的工厂，并且不需要为每个请求构建一个工厂。注入(inject)本身会根据请求发生。换句话说，getInjectable每个请求都会调用方法。你有机会尝试吗？

OTOH，如果您扩展 SingletonTypeInjectableProvider每次都会将相同的对象注入(inject)到您的资源中。

我不确定我是否完全理解您的 Provider执行。我相信像下面这样的东西应该有效。

public class UserProvider extends PerRequestTypeInjectableProvider<AttributeParam, Users>{

    public UserProvider(){
        super(Users.class);
    }

    @Context
    HttpServletRequest request;

    @Override
    public Injectable<Users> getInjectable(ComponentContext cc, AttributeParam a) {

        String attributeValue = AnnotationUtils.getValue(a);

        return new Injectable<Users>(){

            public Users getValue() {
                System.out.println("Called"); //This should be called for each request
                return request.getAttribute(attributeValue);
            }

        };

    }

}

@Provider
@Named("userProviderParamInjector")
public class UserProviderParam implements StringReaderProvider<Users> {

    @Context
    HttpServletRequest request;

    public StringReader<Users> getStringReader(Class<?> type, Type type1, Annotation[] antns) {
        if(type.equals(Users.class) {
           return null;
        }

        String attributeValue = null;
        for(Annotation a : antns) {
            if((a.getClass().getSimpleName()).equals("AttributeParam")){
               attributeValue = (String)AnnotationUtils.getValue(a);
            }
        }

        return new StringReader<Users>(){
            public Users fromString(String string) {
                // Use the value of the *Param or ignore it and use the attributeValue of our custom annotation.
                return request.getAttribute(attributeValue);
            }

        };

    }

}

@Path("/user/")
@Named
public class UserResource {

    @Path("{id}")
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public Result<Users> get(@AttributeParam("foo") @PathParam("id") Users user) {
    ...
    }

}

关于java - Jersey :InjectableProvider 没有被选中 - Spring，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/11944434/