java - GET 请求失败，JAX-RS : Could not find MessageBodyWriter for response object of type: java. util.ArrayList 媒体类型:text/html

Question

我正在使用 JEE7 构建一个带有 JAX-RS 的示例客户端-服务器。我正在使用 Wildfly 10.1

我关注了 this 中的那个人视频。下面是在应用服务器上运行的war的代码:

boundary 包包含服务

package pl.devcrowd.virtual.business.chickens.boundary;

import java.util.List;

import javax.ejb.Stateless;
import javax.inject.Inject;

import pl.devcrowd.virtual.business.chickens.controls.ChickenStore;
import pl.devcrowd.virtual.business.chickens.entity.Chicken;

@Stateless
public class ChickenService {

    @Inject
    ChickenStore cs;

    public List<Chicken> getAllChickens() {
        return this.cs.all();
    }

    public void save(Chicken chicken) {
        this.cs.save(chicken);
    }
}

和资源

package pl.devcrowd.virtual.business.chickens.boundary;

import java.util.List;

import javax.inject.Inject;
import javax.json.JsonObject;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;

import pl.devcrowd.virtual.business.chickens.entity.Chicken;

@Path("chickens")
public class ChickensResource {

    @Inject
    ChickenService cs;

    @GET
    public List<Chicken> chickens() {
        return cs.getAllChickens();
    }

    @POST
    public void save(JsonObject chicken) {
        String name = chicken.getString("name");
        int age = chicken.getInt("age");
        cs.save(new Chicken(name, age));
    }
}

control 包包含在此示例中几乎无用的存储

package pl.devcrowd.virtual.business.chickens.controls;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import pl.devcrowd.virtual.business.chickens.entity.Chicken;

public class ChickenStore {

    @PersistenceContext
    EntityManager em;

    public void save(Chicken chicken) {
        em.merge(chicken);
    }

    public List<Chicken> all() {
        return this.em
                .createNamedQuery("all", Chicken.class)
                .getResultList();
    }
}

entity 包包含实体:

package pl.devcrowd.virtual.business.chickens.entity;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.NamedQuery;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlRootElement;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement
@Entity
@NamedQuery(name="all", query = "SELECT c FROM Chicken C")
public class Chicken {

    @Id
    @GeneratedValue
    private long id;
    private String name;
    private int age;

    public Chicken() {}

    public Chicken(String name, int age) {
        this.name = name;
        this.age = age;
    }
}

父包包含我实现的 Jax-RS 应用程序类，我希望正确:

package pl.devcrowd.virtual.business;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

import javax.ws.rs.ApplicationPath;
import javax.ws.rs.core.Application;

import pl.devcrowd.virtual.business.chickens.boundary.ChickensResource;

/**
 * Configures a JAX-RS endpoint. Delete this class, if you are not exposing
 * JAX-RS resources in your application.
 *
 * @author airhacks.com
 */
@ApplicationPath("resources")
public class JAXRSConfiguration extends Application {
    public Set<Class<?>> getClasses() {
        return new HashSet<Class<?>>(Arrays.asList(ChickensResource.class));
    }
}

现在我正在尝试执行这样的 GET 请求

RestClient get = RestClient.create().method("GET")
        .host("http://localhost:8080/DevCrowd")
        .path("resources/chickens");
GluonObservableList<Chicken> sample = DataProvider.retrieveList(
        get.createListDataReader(Chicken.class));
System.out.println(sample);

鸡在哪里

public class Chicken {

    private String name;
    private int age;

    public Chicken(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

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

    public String getName() {
        return name;
    }
}

我收到错误:

05:59:17,019 ERROR [org.jboss.resteasy.resteasy_jaxrs.i18n] (default task-3) RESTEASY002005: Failed executing GET /chickens: org.jboss.resteasy.core.NoMessageBodyWriterFoundFailure: Could not find MessageBodyWriter for response object of type: java.util.ArrayList of media type: text/html
    at org.jboss.resteasy.core.ServerResponseWriter.writeNomapResponse(ServerResponseWriter.java:66)
    at org.jboss.resteasy.core.SynchronousDispatcher.writeResponse(SynchronousDispatcher.java:473)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:422)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:209)
    at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:221)
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56)
    at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
    at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
    at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
    at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
    at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
    at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
    at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
    at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
    at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
    at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
    at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:292)
    at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:81)
    at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:138)
    at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:135)
    at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
    at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
    at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:272)
    at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
    at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:104)
    at io.undertow.server.Connectors.executeRootHandler(Connectors.java:202)
    at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:805)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

我做错了什么？

Answer 1

据我所知，客户端调用 mediatype text/html。但是objectmapper不知道如何为arraylist编写html。您期望 xml 或 json 哪种格式？

@Path("chickens")
public class ChickensResource {

    @Inject
    ChickenService cs;

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public List<Chicken> chickens() {
        return cs.getAllChickens();
    }

    @POST
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public void save(JsonObject chicken) {
        String name = chicken.getString("name");
        int age = chicken.getInt("age");
        cs.save(new Chicken(name, age));
    }
}

另一种解决方案是在请求中设置正确的请求内容类型:获取 header :

 Accept: application/json

帖子标题:

Accept: application/json
Content-Type: application/json

Accept header 说明响应应采用哪种格式。Content-Type header 说明请求有效负载的格式。

内容类型:

HTML --> text/html
JSON --> application/json
XML --> application/xml

编辑:我认为该帖子也有同样的问题。我们现在告诉这些方法，它们使用 json 作为输入数据并返回 json 作为输出数据(生成)。

但是这些数据真的是在请求中设置的吗？您能发布一下您是如何构建该帖子的吗？

为了匹配这些方法，请求中需要有这两个 header :Accept: application/json 表示客户端期望哪种格式。这应该与设置输出格式的服务中的 @Produces 相匹配。Content-Type: application/json 这是我认为缺少的一个，说明了 POST 有效负载的格式，这应该与服务器输入匹配 @Consumes