30分钟学会使用Spring Web Services基础开发

时隔一年终于又推出了一篇30分钟系列，上一篇《30分钟学会反向Ajax》是2016年7月的事情了。时光荏苒，岁月穿梭。虽然一直还在从事Java方面的开发工作，但是私下其实更喜欢使用C++。不过今天，我们要再次回归到Java的主题，来谈一谈如何使用——Spring Web Services框架。

Spring Web Services(下简称ws)本质上是基于SpringBoot的项目，因此如果有对SpringBoot不太了解的同学，回头再来看比较合适。

ws分为server端与client端两个部分，本文旨在介绍框架搭建的流程与重点。

一、ws.server端搭建

建立Server的关键是首先建立xsd文件。xsd文件是xml文件的定义与基础，你希望别人如何访问与获取你的数据都需要在xsd文件中说明。

countries.xsd

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:tns="http://learnhow.org/ws/schema" targetNamespace="http://learnhow.org/ws/schema"
    elementFormDefault="qualified">
    <xs:element name="getCountryRequest">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="name" type="xs:string" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>

    <xs:element name="getCountryResponse">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="country" type="tns:country" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>

    <xs:complexType name="country">
        <xs:sequence>
            <xs:element name="name" type="xs:string" />
            <xs:element name="population" type="xs:int" />
            <xs:element name="capital" type="xs:string" />
            <xs:element name="currency" type="tns:currency" />
            <xs:element name="language" type="tns:language" />
        </xs:sequence>
    </xs:complexType>

    <xs:simpleType name="currency">
        <xs:restriction base="xs:string">
            <xs:enumeration value="GBP" />
            <xs:enumeration value="EUR" />
            <xs:enumeration value="PLN" />
        </xs:restriction>
    </xs:simpleType>

    <xs:complexType name="language">
        <xs:sequence>
            <xs:element name="name" type="xs:string" />
        </xs:sequence>
    </xs:complexType>
</xs:schema>

users.xsd

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    xmlns:tns="http://learnhow.org/ws/schema" targetNamespace="http://learnhow.org/ws/schema"
    elementFormDefault="qualified">
    <xs:element name="getUserRequest">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="name" type="xs:string" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>

    <xs:element name="getUserResponse">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="user" type="tns:user" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>
    
    <xs:complexType name="user">
        <xs:sequence>
            <xs:element name="name" type="xs:string" />
            <xs:element name="gender" type="tns:gender" />
            <xs:element name="age" type="xs:int" />
            <xs:element name="address" type="xs:string" />
        </xs:sequence>
    </xs:complexType>
    
    <xs:simpleType name="gender">
        <xs:restriction base="xs:string">
            <xs:enumeration value="MALE" />
            <xs:enumeration value="FEMALE" />
        </xs:restriction>
    </xs:simpleType>
</xs:schema>

这两个文件默认请存放于 src/main/resources 目录下，如下图所示：

建立完成以后我们可以着手编写pom.xml文件，即建立工程依赖。

<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>org.learnhow</groupId>
    <artifactId>ws.server</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>ws.server</name>
    <url>http://maven.apache.org</url>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.4.RELEASE</version>
    </parent>
    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web-services</artifactId>
        </dependency>
        <dependency>
            <groupId>wsdl4j</groupId>
            <artifactId>wsdl4j</artifactId>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>jaxb2-maven-plugin</artifactId>
                <version>1.6</version>
                <executions>
                    <execution>
                        <id>xjc</id>
                        <goals>
                            <goal>xjc</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <schemaDirectory>${project.basedir}/src/main/resources/</schemaDirectory>
                    <outputDirectory>${project.basedir}/src/main/java</outputDirectory>
                    <clearOutputDir>false</clearOutputDir>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

重点是最后的一项maven plugin，它会读取resources目录下的xsd文件并在 src/main/java 目录下建立.java文件。需要注意的是代码的package路径是通过xsd的targetNamespace事先指定的。

代码文件被maven创建完成以后代表第一段工作顺利完成。下面我们需要人工编写Endpoint类，即建立对外访问的服务接口。通常你提供了几分xsd文件就应该创建几个Endpoint类。Endpoint本质上是接收一个request，然后经过你的业务逻辑再返回一个response。与传统意义上的浏览器不同，后者通常传输json字符串，而前者则是xml。

CountryEndpoint

package org.learnhow.ws.server;

import org.learnhow.ws.schema.GetCountryRequest;
import org.learnhow.ws.schema.GetCountryResponse;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.ws.server.endpoint.annotation.Endpoint;
import org.springframework.ws.server.endpoint.annotation.PayloadRoot;
import org.springframework.ws.server.endpoint.annotation.RequestPayload;
import org.springframework.ws.server.endpoint.annotation.ResponsePayload;

@Endpoint
public class CountryEndpoint {
    private static final String NAMESPACE_URI = "http://learnhow.org/ws/schema";
    @Autowired
    private CountryRepository countryRepository;

    @PayloadRoot(namespace = NAMESPACE_URI, localPart = "getCountryRequest")
    @ResponsePayload
    public GetCountryResponse getCountry(@RequestPayload GetCountryRequest request) {
        GetCountryResponse response = new GetCountryResponse();
        response.setCountry(countryRepository.findCountry(request.getName()));

        return response;
    }
}

UserEndpoint

package org.learnhow.ws.server;

import org.learnhow.ws.schema.GetUserRequest;
import org.learnhow.ws.schema.GetUserResponse;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.ws.server.endpoint.annotation.Endpoint;
import org.springframework.ws.server.endpoint.annotation.PayloadRoot;
import org.springframework.ws.server.endpoint.annotation.RequestPayload;
import org.springframework.ws.server.endpoint.annotation.ResponsePayload;

@Endpoint
public class UserEndpoint {
    private static final String NAMESPACE_URI = "http://learnhow.org/ws/schema";
    @Autowired
    private UserRepository userRepository;

    @PayloadRoot(namespace = NAMESPACE_URI, localPart = "getUserRequest")
    @ResponsePayload
    public GetUserResponse getUser(@RequestPayload GetUserRequest request) {
        GetUserResponse response = new GetUserResponse();
        response.setUser(userRepository.findUser(request.getName()));
        return response;
    }
}

很显然你的业务逻辑应该封装在CountryRepository和UserRepository对象里。接下来创建CountryRepository对象。

CountryRepository

package org.learnhow.ws.server;

import java.util.HashMap;
import java.util.Map;

import javax.annotation.PostConstruct;

import org.learnhow.ws.schema.Country;
import org.learnhow.ws.schema.Currency;
import org.learnhow.ws.schema.Language;
import org.springframework.stereotype.Component;

@Component
public class CountryRepository {
    private static final Map<String, Country> countries = new HashMap<>();

    @PostConstruct
    public void initData() {
        Country spain = new Country();
        spain.setName("Spain");
        spain.setCapital("Madrid");
        spain.setCurrency(Currency.EUR);
        spain.setPopulation(46704314);
        Language spanish = new Language();
        spanish.setName("spanish");
        spain.setLanguage(spanish);

        Country poland = new Country();
        poland.setName("Poland");
        poland.setCapital("Warsaw");
        poland.setCurrency(Currency.PLN);
        poland.setPopulation(38186860);
        Language polish = new Language();
        polish.setName("polish");
        poland.setLanguage(polish);

        Country uk = new Country();
        uk.setName("United Kingdom");
        uk.setCapital("London");
        uk.setCurrency(Currency.GBP);
        uk.setPopulation(63705000);
        Language english = new Language();
        english.setName("english");
        uk.setLanguage(english);

        countries.put(spain.getName(), spain);
        countries.put(poland.getName(), poland);
        countries.put(uk.getName(), uk);
    }
    
    public Country findCountry(String name) {
        return countries.get(name);
    }
}

UserRepository（略）

最后是编写configuration，它是整个框架调用的核心。

package org.learnhow.ws.server;

import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.ws.config.annotation.EnableWs;
import org.springframework.ws.config.annotation.WsConfigurerAdapter;
import org.springframework.ws.transport.http.MessageDispatcherServlet;
import org.springframework.ws.wsdl.wsdl11.DefaultWsdl11Definition;
import org.springframework.xml.xsd.SimpleXsdSchema;
import org.springframework.xml.xsd.XsdSchema;

@EnableWs
@Configuration
public class WebServiceConfig extends WsConfigurerAdapter {
    @Bean
    public ServletRegistrationBean messageDispatcherServlet(ApplicationContext applicationContext) {
        MessageDispatcherServlet servlet = new MessageDispatcherServlet();
        servlet.setApplicationContext(applicationContext);
        servlet.setTransformWsdlLocations(true);
        return new ServletRegistrationBean(servlet, "/ws/*");
    }

    @Bean(name = "countries")
    public DefaultWsdl11Definition defaultWsdl11DefinitionCountry() {
        DefaultWsdl11Definition wsdl11Definition = new DefaultWsdl11Definition();
        wsdl11Definition.setPortTypeName("CountriesPort");
        wsdl11Definition.setLocationUri("/ws");
        wsdl11Definition.setTargetNamespace("http://learnhow.org/ws/schema");
        wsdl11Definition.setSchema(countriesSchema());
        return wsdl11Definition;
    }

    @Bean(name = "users")
    public DefaultWsdl11Definition defaultWsdl11DefinitionUser() {
        DefaultWsdl11Definition wsdl11Definition = new DefaultWsdl11Definition();
        wsdl11Definition.setPortTypeName("CountriesPort");
        wsdl11Definition.setLocationUri("/ws");
        wsdl11Definition.setTargetNamespace("http://learnhow.org/ws/schema");
        wsdl11Definition.setSchema(usersSchema());
        return wsdl11Definition;
    }

    @Bean
    public XsdSchema countriesSchema() {
        return new SimpleXsdSchema(new ClassPathResource("countries.xsd"));
    }

    @Bean
    public XsdSchema usersSchema() {
        return new SimpleXsdSchema(new ClassPathResource("users.xsd"));
    }

}

最后一步：编写启动项Application

package org.learnhow.ws;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
    
}

完成的目录结构如下：

二、测试

启动application，打开浏览器访问:http://localhost:8080/ws/countries.wsdl与http://localhost:8080/ws/users.wsdl 如果页面分别展示了两份xml文件代表服务器已经可以正常运行了。也可以用SoapUI Pro进一步测试数据的读取和发送是否正常。

三、ws.client端搭建

如果说server端是通过xsd产生java与WSDL的过程那么client端就恰恰相反。我们还是使用maven工具通过服务器暴露在外的wsdl文件建立java对象。首先编辑pom.xml文件配置依赖和wsdl访问路径。

<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>org.learnhow</groupId>
    <artifactId>ws.client</artifactId>
    <packaging>jar</packaging>
    <version>0.0.1-SNAPSHOT</version>
    
    <properties>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.4.RELEASE</version>
    </parent>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.ws</groupId>
            <artifactId>spring-ws-core</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.jvnet.jaxb2.maven2</groupId>
                <artifactId>maven-jaxb2-plugin</artifactId>
                <version>0.13.2</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <schemaLanguage>WSDL</schemaLanguage>
                    <generatePackage>ws.wsdl</generatePackage>
                    <schemas>
                        <schema>
                            <url>http://localhost:8080/ws/countries.wsdl</url>
                        </schema>
                        <schema>
                            <url>http://localhost:8080/ws/users.wsdl</url>
                        </schema>
                    </schemas>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

这里要注意，如果此时你已经将server的进程停止，也就是wsdl无法访问，pom.xml文件会报错。看上去大概会像这样：

正常情况下maven会自动帮你在target目录下建立java对象，目录结构如下：

如果你发现无法正常建立java对象，请首先检查以下两点：

maven引入的依赖是否完整：国内的网络环境不是很好，有时候通过maven搭建环境经常会在运行时报出各种莫名其妙的错误。其中绝大多数其实都是由于依赖引入不完整造成的。此时你可能需要对Maven Dependencies目录下的jar包逐一检查。

maven结构错误：maven的版本很多，不同的版本间可能在元素的结构定义上有所差距。如果在<plugins>节点报错可以考虑在外层再包一层<pluginManagement>节点。具体原因我也没有深究，只能说“有时管用”，如果你对maven有深入的了解也希望告诉我。

如果以上环境你进行的都很顺利，那么恭喜你80%的工作已经完成了。

下面是编写client客户端代码：

package org.learnhow.ws.client;

import org.springframework.ws.client.core.support.WebServiceGatewaySupport;
import org.springframework.ws.soap.client.core.SoapActionCallback;

import ws.wsdl.GetCountryRequest;
import ws.wsdl.GetCountryResponse;

public class CountryClient extends WebServiceGatewaySupport {
    public static final String URI = "http://localhost:8080/ws";
    public static final String SOAPACTION = "http://learnhow.org/ws/schema/getUserRequest";

    public GetCountryResponse getCountry(String countryName) {
        GetCountryRequest request = new GetCountryRequest();
        request.setName(countryName);

        GetCountryResponse response = (GetCountryResponse) getWebServiceTemplate().marshalSendAndReceive(URI, request,
                new SoapActionCallback(SOAPACTION));

        return response;
    }
}

UserClient（略）

然后依然是创建configuration供框架调用

package org.learnhow.ws.client;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.oxm.jaxb.Jaxb2Marshaller;

@Configuration
public class AppConfiguration {
    @Bean
    public Jaxb2Marshaller marshaller() {
        Jaxb2Marshaller marshaller = new Jaxb2Marshaller();
        marshaller.setContextPath("ws.wsdl");
        return marshaller;
    }

    @Bean("country")
    public CountryClient counrtyClient(Jaxb2Marshaller marshaller) {
        CountryClient client = new CountryClient();
        client.setDefaultUri(CountryClient.URI);
        client.setMarshaller(marshaller);
        client.setUnmarshaller(marshaller);
        return client;
    }

    @Bean("user")
    public UserClient userClient(Jaxb2Marshaller marshaller) {
        UserClient client = new UserClient();
        client.setDefaultUri(UserClient.URI);
        client.setMarshaller(marshaller);
        client.setUnmarshaller(marshaller);
        return client;
    }
}

最后是编写Application启动项

package org.learnhow.ws;

import org.learnhow.ws.client.CountryClient;
import org.learnhow.ws.client.UserClient;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

import ws.wsdl.GetCountryResponse;
import ws.wsdl.GetUserResponse;

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    CommandLineRunner lookup(CountryClient client) {
        return args -> {
            String countryName = "Spain";

            if (args.length > 0) {
                countryName = args[0];
            }
            GetCountryResponse response = client.getCountry(countryName);
            System.out.println("response: " + response.getCountry().getName());
        };
    }
}

运行application，如果你能看到控制台有 "response: Spain" 打出代表数据已经能够正常获取。

后记：

本文的代码逻辑主要参考了Spring Web Services官网文档。另外WebService除了通过Spring还有多种实现手段，感兴趣的同学可以看看如何使用wsimport工具以及Tomcat发布WebService的例子。这里不再赘述。