通过JAXB将链接插入RESTEasy XML结果

Question

我想通过RESTeasy/JAXB将链接插入XML .我试图使用我的代码的文档,但这不起作用,所以我只是在文档中编写给定的示例:它仍然不起作用,我不知道为什么.

背景:

要在我的JBoss RESTEasy API中实现HATEOAS原则,我必须在我的JAXB XML结果中插入链接,以便客户端可以浏览API.

我现在正试图了解如何做到这一点,但我不确定 文档是否充满错误,或者我只是无法理解示例和解释:

不清楚的东西:

据我所知,你必须使用@AddLinks声明结果应该插入链接.然后我必须再次冗余地(!？)@LinkResource和" 有时 "指定URI构建过程应该来自哪个类(例如@LinkResource(value = car.class)).然后我必须RESTServiceDiscovery在实体类中添加一个,用@XmlElementRef... 注释它但是在RESTServiceDiscovery声明(!？)后,示例中根本没有使用它.

码:

我真的很困惑如何使用所有这些,但当然我自己尝试了很多代码,让它工作.
以下代码就像文档示例:

BookController.java

import java.util.ArrayList;
import java.util.Collection;

import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;

import org.jboss.resteasy.links.AddLinks;
import org.jboss.resteasy.links.LinkResource;

import com.gasx.extsys.datamodel.vo.kplan.Book;

@Path("/")
@Consumes({ "application/xml", "application/json" })
@Produces({ "application/xml", "application/json" })
public class BookController {
    @AddLinks
    @LinkResource(value = Book.class)
    @GET
    @Path("books")
    public Collection<Book> getBooks() {
        ArrayList<Book> res = new ArrayList<Book>();
        res.add(new Book("Robert", "WhySOIsGreat"));
        res.add(new Book("Robert", "JavaUltimateGuide"));
        res.add(new Book("Not Robert", "ThisIsSparta!"));
        return res;
    };

    @AddLinks
    @LinkResource
    @GET
    @Path("book/{id}")
    public Book getBook(@PathParam("id") String id) {
        return new Book("Robert", "WhyIloveJAVA");
    };
} 

Book.java:

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElementRef;
import javax.xml.bind.annotation.XmlID;
import javax.xml.bind.annotation.XmlRootElement;

import org.jboss.resteasy.links.RESTServiceDiscovery;

@XmlRootElement
@XmlAccessorType(XmlAccessType.NONE)
public class Book {
    @XmlAttribute
    private String author = "startAuthor";

    @XmlID
    @XmlAttribute
    private String title = "startTitle";

    @XmlElementRef
    private RESTServiceDiscovery rest;

    public Book() {

    }

    public Book(String author, String title) {
        this.author = author;
        this.title = title;
    }
}

现在调用GET上books或book/1引发此错误:

2014-09-25 11:30:36,188 WARN  [http-/0.0.0.0:8080-1] (org.jboss.resteasy.core.SynchronousDispatcher:135) # Failed executing GET /book/1: org.jboss.resteasy.plugins.providers.jaxb.JAXBMarshalException: com.sun.xml.bind.v2.runtime.IllegalAnnotationsException: 1 counts of IllegalAnnotationExceptions
XmlElementRef points to a non-existent class.

我不知道如何可以工作,所以我试着用下面的代码中手动添加的URI Book.java:

import java.net.URI;
    public Book(String author, String title) {
        this.author = author;
        this.title = title;
        URI uri = URI.create("books/" + title);
        rest = new RESTServiceDiscovery();
        rest.addLink(uri, "self");
    }

但这仍然会引发同样的错误.

Answer 1

我对链接注入不太熟悉,但添加链接的一种简单方法是将javax.ws.rs.core.Links嵌入到JAXB实体类中.它带有一个内置的XmlAdapter,Link.JaxbAdapter它允许LinkJAXB 对该类型进行编组和解组.举个例子,你有一个BookStore包含一个集合的类Books.它也可以Link用来控制导航案例.

@XmlRootElement(name = "bookstore")
public class BookStore {

    private List<Link> links;
    private Collection<Book> books;

    @XmlElementRef
    public Collection<Book> getBooks() {
        return books;
    }

    public void setBooks(Collection<Book> books) {
        this.books = books;
    }

    @XmlElement(name = "link")
    @XmlJavaTypeAdapter(Link.JaxbAdapter.class) 
    public List<Link> getLinks() {
        return links;
    }

    public void setLinks(List<Link> links) {
        this.links = links;
    }

    @XmlTransient
    public URI getNext() {
        if (links == null) {
            return null;
        }
        for (Link link : links) {
            if ("next".equals(link.getRel())) {
                return link.getUri();
            }
        }
        return null;
    }

    @XmlTransient
    public URI getPrevious() {
        if (links == null) {
            return null;
        }
        for (Link link : links) {
            if ("previous".equals(link.getRel())) {
                return link.getUri();
            }
        }
        return null;
    }
}

该Book班只是一个普通的根元素JAXB类

@XmlRootElement
public class Book {

    @XmlAttribute
    private String author;

    @XmlAttribute
    private String title;

    public Book() {}

    public Book(String title, String author) {
        this.title = title;
        this.author = author;
    }
}

在BookResource课堂上,我们基本上可以根据您想要表示的链接所需的逻辑按需添加链接.在下面的示例中,存在的用于我添加五本书,与递增IDS书籍内存中的分贝(这类被用作有状态单例类只是例子).当请求进入时,将返回一个或两个链接BookStore.根据请求的ID,我们将添加"下一个"和/或之前的"链接.链接将包含rel我们在BookStore课堂上引用的内容.

@Path("/books")
public class BookResource {

    private final Map<Integer, Book> booksDB 
            = Collections.synchronizedMap(new LinkedHashMap<Integer, Book>());
    private final AtomicInteger idCounter = new AtomicInteger();

    public BookResource() {
        Book book = new Book("Book One", "Author One");
        booksDB.put(idCounter.incrementAndGet(), book);

        book = new Book("Book Two", "Author Two");
        booksDB.put(idCounter.incrementAndGet(), book);

        book = new Book("Book Three", "Author Three");
        booksDB.put(idCounter.incrementAndGet(), book);

        book = new Book("Book Four", "Author Four");
        booksDB.put(idCounter.incrementAndGet(), book);

        book = new Book("Book Five", "Author Five");
        booksDB.put(idCounter.incrementAndGet(), book);
    }

    @GET
    @Formatted
    @Path("/{id}")
    @Produces(MediaType.APPLICATION_XML)
    public BookStore getBook(@Context UriInfo uriInfo, @PathParam("id") int id) {
        List<Link> links = new ArrayList<>();
        Collection<Book> books = new ArrayList<>();

        UriBuilder uriBuilder = uriInfo.getBaseUriBuilder();
        uriBuilder.path("books");
        uriBuilder.path("{id}");

        Book book = booksDB.get(id);
        if (book == null) {
            throw new WebApplicationException(Response.Status.NOT_FOUND);
        }

        synchronized(booksDB) {
            if (id + 1 <= booksDB.size()) {
                int next = id + 1;
                URI nextUri = uriBuilder.clone().build(next);
                Link link = Link.fromUri(nextUri).rel("next").type(MediaType.APPLICATION_XML).build();
                links.add(link);
            }
            if (id - 1 > 0) {
                int previous = id - 1;
                URI nextUri = uriBuilder.clone().build(previous);
                Link link = Link.fromUri(nextUri).rel("previous").type(MediaType.APPLICATION_XML).build();
                links.add(link);
            }
        }

        books.add(book);
        BookStore bookStore = new BookStore();
        bookStore.setLinks(links);
        bookStore.setBooks(books);
        return bookStore;
    }
}

在测试用例中,我们请求第三本书,我们可以看到内存数据库中有"下一页"和"上一页"书籍的链接.我们还要求getNext()我们BookStore检索数据库中的下一本书,结果将带有两个不同的链接.

public class BookResourceTest {

    private static Client client;

    @BeforeClass
    public static void setUpClass() {
        client = ClientBuilder.newClient();
    }

    @AfterClass
    public static void tearDownClass() {
        client.close();
    }

    @Test
    public void testBookResourceLinks() throws Exception {
        String BASE_URL = "http://localhost:8080/jaxrs-stackoverflow-book/rest/books/3";
        WebTarget target = client.target(BASE_URL);
        String xmlResult = target.request().accept(MediaType.APPLICATION_XML).get(String.class);
        System.out.println(xmlResult);

        Unmarshaller unmarshaller = JAXBContext.newInstance(BookStore.class).createUnmarshaller();
        BookStore bookStore = (BookStore)unmarshaller.unmarshal(new StringReader(xmlResult));
        URI next = bookStore.getNext();

        WebTarget nextTarget = client.target(next);
        String xmlNextResult = nextTarget.request().accept(MediaType.APPLICATION_XML).get(String.class);
        System.out.println(xmlNextResult);
    }
}

结果:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<bookstore>
    <book author="Author Three" title="Book Three"/>
    <link href="http://localhost:8080/jaxrs-stackoverflow-book/rest/books/4" rel="next" type="application/xml"/>
    <link href="http://localhost:8080/jaxrs-stackoverflow-book/rest/books/2" rel="previous" type="application/xml"/>
</bookstore>

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<bookstore>
    <book author="Author Four" title="Book Four"/>
    <link href="http://localhost:8080/jaxrs-stackoverflow-book/rest/books/5" rel="next" type="application/xml"/>
    <link href="http://localhost:8080/jaxrs-stackoverflow-book/rest/books/3" rel="previous" type="application/xml"/>
</bookstore>

仅供参考,我正在使用Resteasy 3.0.8和Wildfly 8.1

更新:使用自动发现

所以我尝试了参考指南示例,我无法重现您的问题.不确定你的完整环境,但这是我正在使用的

• Wildfly 8.1
• Resteasy 3.0.8
• Maven的

这是代码

应用类

@ApplicationPath("/rest")
public class BookApplication extends Application {
    @Override
    public Set<Class<?>> getClasses() {
       Set<Class<?>> classes = new HashSet<>();
       classes.add(Bookstore.class);
       return classes;
   }
}

资源类

@Path("/books")
@Produces({"application/xml", "application/json"})
public class Bookstore {

    @AddLinks
    @LinkResource(value = Book.class)
    @GET
    @Formatted
    public Collection<Book> getBooks() {
        List<Book> books = new ArrayList<>();
        books.add(new Book("Book", "Author"));
        return books;
    }
}

预订课程

@XmlRootElement
@XmlAccessorType(XmlAccessType.NONE)
public class Book {
    @XmlAttribute
    private String author;
    @XmlID @XmlAttribute
    private String title; 
    @XmlElementRef
    private RESTServiceDiscovery rest;

    public Book() {}

    public Book(String title, String author) {
        this.title = title;
        this.author = author;
    }
}

pom.xml(也许你缺少一些依赖项 - 注意下面的resteasy-client和resteasy-servlet-initializer仅用于测试)

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" 
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 
                             http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.underdogdevs.web</groupId>
    <artifactId>jaxrs-stackoverflow-user</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <name>jaxrs-stackoverflow-user</name>

    <properties>
        <endorsed.dir>${project.build.directory}/endorsed</endorsed.dir>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.jboss.resteasy</groupId>
            <artifactId>resteasy-jackson2-provider</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jboss.resteasy</groupId>
            <artifactId>resteasy-jaxb-provider</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jboss.resteasy</groupId>
            <artifactId>resteasy-jaxrs</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jboss.resteasy</groupId>
            <artifactId>jaxrs-api</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jboss.resteasy</groupId>
            <artifactId>resteasy-links</artifactId>
        </dependency>
        <dependency>
            <groupId>org.jboss.resteasy</groupId>
            <artifactId>resteasy-client</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.jboss.resteasy</groupId>
            <artifactId>resteasy-servlet-initializer</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>javax</groupId>
            <artifactId>javaee-web-api</artifactId>
            <version>7.0</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.wildfly.bom</groupId>
                <artifactId>jboss-javaee-7.0-with-resteasy</artifactId>
                <version>8.1.0.Final</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.wildfly.bom</groupId>
                <artifactId>jboss-javaee-7.0-with-tools</artifactId>
                <version>8.1.0.Final</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <finalName>${project.artifactId}</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                    <compilerArguments>
                        <endorseddirs>${endorsed.dir}</endorseddirs>
                    </compilerArguments>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>2.3</version>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-dependency-plugin</artifactId>
                <version>2.6</version>
                <executions>
                    <execution>
                        <phase>validate</phase>
                        <goals>
                            <goal>copy</goal>
                        </goals>
                        <configuration>
                            <outputDirectory>${endorsed.dir}</outputDirectory>
                            <silent>true</silent>
                            <artifactItems>
                                <artifactItem>
                                    <groupId>javax</groupId>
                                    <artifactId>javaee-endorsed-api</artifactId>
                                    <version>7.0</version>
                                    <type>jar</type>
                                </artifactItem>
                            </artifactItems>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

在浏览器中正常工作

适用于客户端api

public class BookTest {
    private static Client client;
    @BeforeClass
    public static void setUpClass() {
        client = ClientBuilder.newClient();
    }
    @AfterClass
    public static void tearDownClass() {
        client.close();
    }

    @Test
    public void testBookLink() {
        String BASE_URL
                = "http://localhost:8080/jaxrs-stackoverflow-user/rest/books";
        WebTarget target = client.target(BASE_URL);
        String result = target.request()
                .accept(MediaType.APPLICATION_XML).get(String.class);
        System.out.println(result);
    }
}

结果

Running jaxrs.book.test.BookTest
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<collection xmlns:atom="http://www.w3.org/2005/Atom">
    <book author="Author" title="Book">
        <atom:link rel="list" href="http://localhost:8080/jaxrs-stackoverflow-user/rest/books"/>
    </book>
</collection>

至于你的不清楚的东西

使用JAX-RS方法注释,@AddLinks以指示您希望在响应实体中注入Atom链接.

这是为了表明该方法将使用链接注入.

注释您希望Atom链接的JAX-RS方法@LinkResource,以便RESTEasy知道要为哪些资源创建哪些链接.

这允许您自定义注入的链接和实体.8.2.4.指定哪些J​​AX-RS方法与哪些资源的关联更深入.

将RESTServiceDiscovery字段添加到您希望注入Atom链接的资源类中.

"注入"意味着框架将为您实例化,因此您永远不必自己明确地执行此操作(正如您尝试的那样).也许对依赖注入和控制反转(IoC)进行一些研究

祝好运.希望这一切都有帮助.