java - 我通过浏览器访问下面的 webservice 方法时遇到异常

Question

package com.rest.webservice;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

@Path(value = "Sample")
public class SampleService {

@Produces(value=MediaType.TEXT_PLAIN)
@GET
@Path(value="price/{bookName}")
public int price(@PathParam(value="bookName") String bookName){
    return 50;
}
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<display-name>Jersey1.x</display-name>
<servlet>
    <servlet-name>abc</servlet-name>
    <servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
    <init-param>
        <param-name>com.sun.jersey.config.property.packages</param-name>
        <param-value>com.rest.webservice</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
    <servlet-name>abc</servlet-name>
    <url-pattern>/rest/*</url-pattern>
</servlet-mapping>

我在通过浏览器访问以下 Webservice 方法时遇到异常。

请求网址:http://localhost:9090/Jersey1.x/rest/Sample/price/java

Feb 21, 2015 9:30:27 AM com.sun.jersey.spi.container.ContainerResponse logException
SEVERE: Mapped exception to response: 500 (Internal Server Error)
javax.ws.rs.WebApplicationException: com.sun.jersey.api.MessageException: A message body writer for Java class java.lang.Integer, and Java type int, and MIME media type text/plain was not found.

    at com.sun.jersey.spi.container.ContainerResponse.write(ContainerResponse.java:284)
    at com.sun.jersey.server.impl.application.WebApplicationImpl._handleRequest(WebApplicationImpl.java:1510)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1419)
    at com.sun.jersey.server.impl.application.WebApplicationImpl.handleRequest(WebApplicationImpl.java:1409)
    at com.sun.jersey.spi.container.servlet.WebComponent.service(WebComponent.java:409)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:540)
    at com.sun.jersey.spi.container.servlet.ServletContainer.service(ServletContainer.java:715)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:314)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:717)
Caused by: com.sun.jersey.api.MessageException: A message body writer for Java class java.lang.Integer, and Java type int, and MIME media type text/plain was not found.

    ... 28 more

Answer 1

A message body writer for Java class java.lang.Integer, and Java type int, and MIME media type text/plain was not found.

错误消息告诉您 JAXRS 不知道如何将 int 返回值转换为纯文本。你可能会认为这很愚蠢，但事实就是如此。

尝试从您的方法返回一个 String 而不是 int，例如

return String.valueOf(50)

然后它应该能够将其转换为纯文本响应。

更一般地说，如果可以避免的话，以纯文本形式 REST 返回 nakes 值并不是一个好的做法。最好编写能够正确表示您的数据的 JSON 或 XML 响应。

看起来编码原语的功能已添加到 JAX-RS 2.0 规范中(请参阅 JAX_RS_SPEC-218 )，但这仍然是相当新的，您需要 JAX-RS 2.0 实现。