最近参照Dubbo官网“快速开始”的案例写一个Demo，没想到差点被劝退。
主程序如下：
package com.example.dubbo.main;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Provider {
public static void main(String[] args) throws Exception {
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"provider.xml"});
context.start();
System.out.println("启动完成......");
System.in.read(); // 按任意键退出
}
}配置文件如下：
启动后控制台日志主要如下：
[main] DEBUG org.springframework.context.support.ClassPathXmlApplicationContext - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@6f1fba17没错，它就是卡在这一行一直没有反应。
然后过一段时间就报下面这个异常：
21:49:03.450 [main] DEBUG org.springframework.beans.factory.xml.ResourceEntityResolver - Could not resolve XML entity [http://dubbo.apache.org/schema/dubbo/dubbo.xsd] through URL [https://dubbo.apache.org/schema/dubbo/dubbo.xsd]
java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:75)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:476)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:218)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:200)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:162)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:394)
at java.net.Socket.connect(Socket.java:606)
at sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:303)
at sun.security.ssl.BaseSSLSocketImpl.connect(BaseSSLSocketImpl.java:173)
at sun.net.NetworkClient.doConnect(NetworkClient.java:180)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:499)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:594)
at sun.net.www.protocol.https.HttpsClient.(HttpsClient.java:263)
at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:366)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:207)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1167)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1061)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:193)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1584)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1512)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:268)
at java.net.URL.openStream(URL.java:1092)
at org.springframework.beans.factory.xml.ResourceEntityResolver.resolveEntity(ResourceEntityResolver.java:118)
at com.sun.org.apache.xerces.internal.util.EntityResolverWrapper.resolveEntity(EntityResolverWrapper.java:110)
at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.resolveEntity(XMLEntityManager.java:1081)
at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaLoader.resolveDocument(XMLSchemaLoader.java:655)
at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.findSchemaGrammar(XMLSchemaValidator.java:2681)
at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.getGlobalElementDecl(XMLSchemaValidator.java:1626)
at com.sun.org.apache.xerces.internal.impl.xs.SubstitutionGroupHandler.getMatchingElemDecl(SubstitutionGroupHandler.java:76)
at com.sun.org.apache.xerces.internal.impl.xs.models.XSDFACM.oneTransition(XSDFACM.java:300)
at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.handleStartElement(XMLSchemaValidator.java:1921)
at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.emptyElement(XMLSchemaValidator.java:836)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:352)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2786)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:605)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:113)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:507)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:867)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:796)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:142)
at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:247)
at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:339)
at org.springframework.beans.factory.xml.DefaultDocumentLoader.loadDocument(DefaultDocumentLoader.java:77)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadDocument(XmlBeanDefinitionReader.java:432)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:390)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:338)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:310)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:196)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:232)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:203)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:265)
at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:128)
at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:94)
at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:130)
at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:671)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:553)
at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:144)
at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:95)
at com.example.dubbo.main.Provider.main(Provider.java:7)
21:49:24.508 [main] WARN org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Ignored XML validation warning
org.xml.sax.SAXParseException: schema_reference.4: 无法读取方案文档 'http://dubbo.apache.org/schema/dubbo/dubbo.xsd', 原因为 1) 无法找到文档; 2) 无法读取文档; 3) 文档的根元素不是 。
at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.createSAXParseException(ErrorHandlerWrapper.java:204)
at com.sun.org.apache.xerces.internal.util.ErrorHandlerWrapper.warning(ErrorHandlerWrapper.java:100)
at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:392)
at com.sun.org.apache.xerces.internal.impl.XMLErrorReporter.reportError(XMLErrorReporter.java:306)
at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.reportSchemaErr(XSDHandler.java:4208)
at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.reportSchemaWarning(XSDHandler.java:4199)
at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.getSchemaDocument1(XSDHandler.java:2525)
at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.getSchemaDocument(XSDHandler.java:2221)
at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.parseSchema(XSDHandler.java:581)
at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaLoader.loadSchema(XMLSchemaLoader.java:610)
at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.findSchemaGrammar(XMLSchemaValidator.java:2697)
at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.getGlobalElementDecl(XMLSchemaValidator.java:1626)
at com.sun.org.apache.xerces.internal.impl.xs.SubstitutionGroupHandler.getMatchingElemDecl(SubstitutionGroupHandler.java:76)
at com.sun.org.apache.xerces.internal.impl.xs.models.XSDFACM.oneTransition(XSDFACM.java:300)
at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.handleStartElement(XMLSchemaValidator.java:1921)
at com.sun.org.apache.xerces.internal.impl.xs.XMLSchemaValidator.emptyElement(XMLSchemaValidator.java:836)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.scanStartElement(XMLNSDocumentScannerImpl.java:352)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2786)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:605)
at com.sun.org.apache.xerces.internal.impl.XMLNSDocumentScannerImpl.next(XMLNSDocumentScannerImpl.java:113)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFrag服务器托管网mentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:507)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:867)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:796)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:142)
at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:247)
at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:339)
at org.springframework.beans.factory.xml.DefaultDocumentLoader.loadDocument(DefaultDocumentLoader.java:77)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadDocument(XmlBeanDefinitionReader.java:432)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.doLoadBeanDefinitions(XmlBeanDefinitionReader.java:390)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:338)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:310)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:196)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:232)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:203)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:265)
at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:128)
at org.springframework.context.support.AbstractXmlApplicationContext.loadBeanDefinitions(AbstractXmlApplicationContext.java:94)
at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:130)
at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:671)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:553)
at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:144)
at org.springframework.context.support.ClassPathXmlApplicationContext.(ClassPathXmlApplicationContext.java:95)
at com.example.dubbo.main.Provider.main(Provider.java:7)
Caused by: java.net.ConnectException: Connection timed out: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:75)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:476)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:218)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:200)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:162)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:394)
at java.net.Socket.connect(Socket.java:606)
at java.net.Socket.connect(Socket.java:555)
at sun.net.NetworkClient.doConnect(NetworkClient.java:180)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:499)
at sun.net.www.http.HttpClient.openServer(HttpClient.java:594)
at sun.net.www.http.HttpClient.(HttpClient.java:278)
at sun.net.www.http.HttpClient.New(HttpClient.java:375)
at sun.net.www.http.HttpClient.New(HttpClient.java:393)
at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1240)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1167)
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1061)
at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:995)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1584)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1512)
at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(XMLEntityManager.java:646)
at com.sun.org.apache.xerces.internal.impl.XMLVersionDetector.determineDocVersion(XMLVersionDetector.java:150)
at com.sun.org.apache.xerces.internal.impl.xs.opti.SchemaParsingConfig.parse(SchemaParsingConfig.java:583)
at com.sun.org.apache.xerces.internal.impl.xs.opti.SchemaParsingConfig.parse(SchemaParsingConfig.java:686)
at com.sun.org.apache.xerces.internal.impl.xs.opti.SchemaDOMParser.parse(SchemaDOMParser.java:531)
at com.sun.org.apache.xerces.internal.impl.xs.traversers.XSDHandler.getSchemaDocument(XSDHandler.java:2209)
... 35 common frames omitted我一直以为是广播注册中心和找不到dubbo.xsd的问题，因为我本地ping不通那个地址，嘿嘿。然后我就换nacos、zookeeper、simple等注册中心，一个一个换，然后发现都不行。然后又下载dubbo.xsd到本地，并配置到IDEA中，发现还是不行。
直到我重新写了一个dubbo的案例，这一次pom.xml依赖中我就只放一个dubbo的依赖，最后发现程序正常运行，那这么一来，之前都是我的问题。。。
于是又重新检查了一遍，我的项目结构如下（api/consumer/provider都继承parent，consumer和provider中都引入了api）：
父pom.xml配置如下：
4.0.0
com.example
my-dubbo-parent
${revision}
pom
${project.artifactId}
my-dubbo-parent
my-dubbo-api
my-dubbo-provider
my-dubbo-consumer
8
8
8
UTF-8
1.0
2.7.15
2.7.23
org.springframework.boot
spring-boot-dependencies
${spring-boot.version}
pom
import
org.apache.dubbo
dubbo-bom
${dubb服务器托管网o.version}
pom
import
org.springframework.boot
spring-boot-maven-plugin
最后才想起父pom.xml中是用dependencyManagement管理的，子pom.xml中要用dubbo则需要再次声明dubbo依赖。(天哪，怎么会是这么低级的问题，杀了我吧！！！)
还有就是需要注意dubbo-bom不要写成dubbo，不然在子pom.xml中就算再次声明也无法编译成功。
一想起这个项目搭建卡在这个环节几天就一顿郁闷，这几天都无心学习了。还是得找个时间学一下Maven管理，对这方面了解的比较少，经常在这吃亏。。。
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