{"id":4304,"date":"2020-08-11T16:02:05","date_gmt":"2020-08-11T10:32:05","guid":{"rendered":"https:\/\/www.h2kinfosys.com\/blog\/?p=4304"},"modified":"2020-08-25T16:29:54","modified_gmt":"2020-08-25T10:59:54","slug":"what-is-the-top-down-bottom-up-approach","status":"publish","type":"post","link":"https:\/\/www.h2kinfosys.com\/blog\/what-is-the-top-down-bottom-up-approach\/","title":{"rendered":"What is the Top-Down Bottom-up Approach?"},"content":{"rendered":"\n

Web Services can be implemented using two approaches top-down bottom-up Approach:<\/p>\n\n\n\n

  1. Top-Down<\/li>
  2. Bottom-up<\/li><\/ol>\n\n\n\n

    Top-Down: <\/strong><\/h2>\n\n\n\n

    In Top-down Approach, the service contract that is WSDL is defined first. Thus, this approach is also known as the contract-first approach. WSDL contains all the information regarding the service, such as service definition, message format, security details, etc. Here the WSDL  is written fist and then the service code.<\/p>\n\n\n\n

    \"TopDown<\/figure><\/div>\n\n\n\n

    Let us implement the Top-down approach. <\/p>\n\n\n\n

    Step 1: <\/strong>Create Maven Dependencies<\/a>.<\/p>\n\n\n\n

    First, add the spring-boot-starter-parent to your project.<\/p>\n\n\n\n

    <parent>\n    <groupId>org.springframework.boot<\/groupId>\n    <artifactId>spring-boot-starter-parent<\/artifactId>\n    <version>2.2.6.RELEASE<\/version>\n<\/parent>\nThen, add the spring-boot-starter-web-services and wsdl4j dependencies.\n<dependency>\n    <groupId>org.springframework.boot<\/groupId>\n    <artifactId>spring-boot-starter-web-services<\/artifactId>\n<\/dependency>\n<dependency>\n    <groupId>wsdl4j<\/groupId>\n    <artifactId>wsdl4j<\/artifactId>\n<\/dependency>\n<\/pre>\n\n\n\n
    Step 2: <\/strong>Create XSD File<\/p>\n\n\n\n
    <?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<xs:schema xmlns:xs=\"https:\/\/www.w3.org\/2001\/XMLSchema\" xmlns:tns=\"https:\/\/www.example.com\/springsoap\/gen\"\n           targetNamespace=\"http:\/\/www.example.com\/springsoap\/gen\" elementFormDefault=\"qualified\">\n     <xs:element name=\"getCountryRequest\">\n        <xs:complexType>\n            <xs:sequence>\n                <xs:element name=\"name\" type=\"xs:string\"\/>\n            <\/xs:sequence>\n        <\/xs:complexType>\n    <\/xs:element>\n \n    <xs:element name=\"getCountryResponse\">\n        <xs:complexType>\n            <xs:sequence>\n                <xs:element name=\"country\" type=\"tns:country\"\/>\n            <\/xs:sequence>\n        <\/xs:complexType>\n    <\/xs:element>\n \n    <xs:complexType name=\"country\">\n        <xs:sequence>\n            <xs:element name=\"name\" type=\"xs:string\"\/>\n            <xs:element name=\"population\" type=\"xs:int\"\/>\n            <xs:element name=\"capital\" type=\"xs:string\"\/>\n            <xs:element name=\"currency\" type=\"tns:currency\"\/>\n        <\/xs:sequence>\n    <\/xs:complexType>\n \n    <xs:simpleType name=\"currency\">\n        <xs:restriction base=\"xs:string\">\n            <xs:enumeration value=\"GBP\"\/>\n            <xs:enumeration value=\"EUR\"\/>\n            <xs:enumeration value=\"PLN\"\/>\n        <\/xs:restriction>\n    <\/xs:simpleType>\n<\/xs:schema><\/pre>\n\n\n\n
    Step 3: <\/strong>We will now generate the Java classes from the XSD file defined. The jaxb2-maven-plugin uses the XJC tool as code generation engine, and XJC compiles the XSD schema file into fully annotated Java classes.<\/p>\n\n\n\n
    We will add and configure the plugin in our pom.xml.<\/strong><\/p>\n\n\n\n
    <plugin>\n    <groupId>org.codehaus.mojo<\/groupId>\n    <artifactId>jaxb2-maven-plugin<\/artifactId>\n    <version>1.6<\/version>\n    <executions>\n        <execution>\n            <id>xjc<\/id>\n            <goals>\n                <goal>xjc<\/goal>\n            <\/goals>\n        <\/execution>\n    <\/executions>\n    <configuration>\n        <schemaDirectory>${project.basedir}\/src\/main\/resources\/<\/schemaDirectory>\n        <outputDirectory>${project.basedir}\/src\/main\/java<\/outputDirectory>\n        <clearOutputDir>false<\/clearOutputDir>\n    <\/configuration>\n<\/plugin>\n<\/pre>\n\n\n\n
    Step 4: <\/strong>Add the SOAP Web Service Endpoint<\/p>\n\n\n\n
    @Component\npublic class CountryRepository {\n     private static final Map<String, Country> countries = new HashMap<>();\n     @PostConstruct\n    public void initData() {\n        \/\/ initialize countries map\n    }\n     public Country findCountry(String name) {\n        return countries.get(name);\n    }\n}\n@Endpoint\npublic class CountryEndpoint {\n     private static final String NAMESPACE_URI = \"https:\/\/www.example.com\/springsoap\/gen\";\n     private CountryRepository countryRepository;\n     @Autowired\n    public CountryEndpoint(CountryRepository countryRepository) {\n        this.countryRepository = countryRepository;\n    }\n     @PayloadRoot(namespace = NAMESPACE_URI, localPart = \"getCountryRequest\")\n    @ResponsePayload\n    public GetCountryResponse getCountry(@RequestPayload GetCountryRequest request) {\n        GetCountryResponse response = new GetCountryResponse();\n        response.setCountry(countryRepository.findCountry(request.getName()));\n         return response;\n    }\n}\n<\/pre>\n\n\n\n
    Step 5: <\/strong>Create SOAP Web Service Configuration Beans.<\/p>\n\n\n\n
    First, create a class to configure the Spring message dispatcher servlet for receiving the request.<\/p>\n\n\n\n
    @EnableWs\n@Configuration\npublic class WebServiceConfig extends WsConfigurerAdapter {\n    \/\/ bean definitions\n}<\/code><\/pre>\n\n\n\n
    @EnableWs will enable the SOAP Web Service<\/a> features in this Spring Boot application. The WebServiceConfig class will then extend the WsConfigurerAdapter base class, which configures the annotation-driven Spring-WS programming model.<\/p>\n\n\n\n
    Now create a MessageDispatcherServlet, which is used for handling SOAP requests.<\/p>\n\n\n\n
    @Bean\npublic ServletRegistrationBean messageDispatcherServlet(ApplicationContext applicationContext) {\n    MessageDispatcherServlet servlet = new MessageDispatcherServlet();\n    servlet.setApplicationContext(applicationContext);\n    servlet.setTransformWsdlLocations(true);\n    return new ServletRegistrationBean(servlet, \"\/ws\/*\");\n}<\/code><\/pre>\n\n\n\n
    Finally, we will create a DefaultWsdl11Definition object that exposes a standard WSDL<\/a> using an XsdSchema. The WSDL name will be the same as of the bean name.<\/p>\n\n\n\n
    @Bean(name = \"countries\")\npublic DefaultWsdl11Definition defaultWsdl11Definition(XsdSchema countriesSchema) {\n    DefaultWsdl11Definition wsdl11Definition = new DefaultWsdl11Definition();\n    wsdl11Definition.setPortTypeName(\"CountriesPort\");\n    wsdl11Definition.setLocationUri(\"\/ws\");\n    wsdl11Definition.setTargetNamespace(\"http:\/\/www.example.com\/springsoap\/gen\");\n    wsdl11Definition.setSchema(countriesSchema);\n    return wsdl11Definition;\n}\n @Bean\npublic XsdSchema countriesSchema() {\n    return new SimpleXsdSchema(new ClassPathResource(\"countries.xsd\"));\n}<\/pre>\n\n\n\n
    Bottom-Up: <\/strong><\/h2>\n\n\n\n
    This approach is exactly the reverse of the Top-down Approach. In this approach, WSDL is created last. Thus, this approach is also known as the contract-last approach. Here the service code is written fist and then the WSDL.<\/p>\n\n\n\n
    \"BottomUp<\/figure>\n\n\n\n
    Let us implement the Bottom-up approach.<\/p>\n\n\n\n
    Step 1: <\/strong>Create a maven project.<\/p>\n\n\n\n
    \"Fig<\/figure>\n\n\n\n
    Provide the details about the maven project.<\/p>\n\n\n\n
    \"Fig<\/figure>\n\n\n\n
    Select the maven-archetype-web app and click on Next.<\/p>\n\n\n\n
    \"Fig<\/figure>\n\n\n\n
    Fill the fields, and click on the Finish button.<\/p>\n\n\n\n
    \"Fig<\/figure>\n\n\n\n
    Step 2: <\/strong>Default POM file will get generated.<\/p>\n\n\n\n
    \"Fig<\/figure>\n\n\n\n
    Add the below jars as a dependency.<\/p>\n\n\n\n
    • Spring-core<\/li>
    • Spring-web<\/li>
    • Spring-context<\/li>
    • cxf-rt-frontend-jaxws<\/li>
    • Cxf-Rt-transports-http<\/li><\/ul>\n\n\n\n
      Step 3: <\/strong>Define the POJO class.<\/p>\n\n\n\n
      \"Fig<\/figure>\n\n\n\n
      Declare the methods in an interface.<\/p>\n\n\n\n
      \"Define<\/figure>\n\n\n\n
      Provide Class implementation.<\/p>\n\n\n\n
      \"Fig<\/figure>\n\n\n\n
      Define cxf bean in XML file and declare this file in web.xml.<\/p>\n\n\n\n
      \"Fig<\/figure>\n\n\n\n
      Listing of web.xml is shown as:<\/p>\n\n\n\n
      \"Fig<\/figure>\n\n\n\n
      Step 4: <\/strong>Deploy the web service using the below URL:<\/p>\n\n\n\n
      http:\/\/localhost:8080\/CustomerService\/services\/<\/span><\/em><\/p>\n\n\n\n
      The page will display the details about the service:<\/p>\n\n\n\n
      \"Fig<\/figure>\n\n\n\n
      The generated WSDL file will be:<\/p>\n\n\n\n
      <wsdl:definitions xmlns:xsd=\"http:\/\/www.w3.org\/2001\/XMLSchema\" xmlns:wsdl=\"http:\/\/schemas.xmlsoap.org\/wsdl\/\" xmlns:tns=\"http:\/\/cxf.ws.example.com\/\"xmlns:soap=\"http:\/\/schemas.xmlsoap.org\/wsdl\/soap\/\" xmlns:ns1=\"http:\/\/schemas.xmlsoap.org\/soap\/http\" name=\"CustomerServiceImplService\" targetNamespace=\"http:\/\/cxf.ws.example.com\/\"> \n<wsdl:types> \n<xs:schema xmlns:xs=\"http:\/\/www.w3.org\/2001\/XMLSchema\" xmlns:tns=\"http:\/\/cxf.ws.example.com\/\" elementFormDefault=\"unqualified\" targetNamespace=\"http:\/\/cxf.ws.example.com\/\"version=\"1.0\">\n<xs:element name=\"addCustomer\" type=\"tns:addCustomer\"\/>\n<xs:element name=\"addCustomerResponse\" type=\"tns:addCustomerResponse\"\/> \n<xs:complexType name=\"addCustomer\"> \n<xs:sequence>\n<xs:element minOccurs=\"0\" name=\"arg0\" type=\"tns:customerVO\"\/>\n<\/xs:sequence>a \n<\/xs:complexType> \n<xs:complexType name=\"customerVO\"> \n<xs:sequence>\n<xs:element name=\"custId\" type=\"xs:int\"\/>\n<xs:element minOccurs=\"0\" name=\"custName\" type=\"xs:string\"\/>\n<\/xs:sequence> \n<\/xs:complexType> \n<xs:complexType name=\"addCustomerResponse\"> \n<xs:sequence>\n<xs:element minOccurs=\"0\" name=\"return\" type=\"xs:string\"\/>\n<\/xs:sequence> \n<\/xs:complexType> \n<\/xs:schema> \n<\/wsdl:types> \n<wsdl:message name=\"addCustomerResponse\">\n<wsdl:part element=\"tns:addCustomerResponse\" name=\"parameters\"><\/wsdl:part>\n<\/wsdl:message> \n<wsdl:message name=\"addCustomer\">\n<wsdl:part element=\"tns:addCustomer\" name=\"parameters\"><\/wsdl:part>\n<\/wsdl:message> \n<wsdl:portType name=\"ICustomerService\"> \n<wsdl:operation name=\"addCustomer\">\n<wsdl:input message=\"tns:addCustomer\" name=\"addCustomer\"><\/wsdl:input>\n<wsdl:output message=\"tns:addCustomerResponse\" name=\"addCustomerResponse\"><\/wsdl:output>\n<\/wsdl:operation> \n<\/wsdl:portType> \n<wsdl:binding name=\"CustomerServiceImplServiceSoapBinding\" type=\"tns:ICustomerService\">\n<soap:binding style=\"document\" transport=\"http:\/\/schemas.xmlsoap.org\/soap\/http\"\/> \n<wsdl:operation name=\"addCustomer\">\n<soap:operation soapAction=\"\" style=\"document\"\/> \n<wsdl:input name=\"addCustomer\">\n<soap:body use=\"literal\"\/>\n<\/wsdl:input> \n<wsdl:output name=\"addCustomerResponse\">\n<soap:body use=\"literal\"\/>\n<\/wsdl:output> \n<\/wsdl:operation> \n<\/wsdl:binding> \n<wsdl:service name=\"CustomerServiceImplService\">\n<wsdl:port binding=\"tns:CustomerServiceImplServiceSoapBinding\" name=\"CustomerServiceImplPort\">\n<soap:address location=\"http:\/\/localhost:8080\/CustomerService\/services\/CustomerServiceImpl\"\/>\n<\/wsdl:port>\n<\/wsdl:service>\n<\/wsdl:definitions><\/pre>\n\n\n\n
      <\/p>\n","protected":false},"excerpt":{"rendered":"
      Web Services can be implemented using two approaches top-down bottom-up Approach: Top-Down Bottom-up Top-Down: In Top-down Approach, the service contract that is WSDL is defined first. Thus, this approach is also known as the contract-first approach. WSDL contains all the information regarding the service, such as service definition, message format, security details, etc. Here the […]<\/p>\n","protected":false},"author":1,"featured_media":4323,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[42],"tags":[637,1195,1194],"class_list":["post-4304","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-java-tutorials","tag-approach","tag-bottom-up","tag-top-down"],"_links":{"self":[{"href":"https:\/\/www.h2kinfosys.com\/blog\/wp-json\/wp\/v2\/posts\/4304","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.h2kinfosys.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.h2kinfosys.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.h2kinfosys.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.h2kinfosys.com\/blog\/wp-json\/wp\/v2\/comments?post=4304"}],"version-history":[{"count":0,"href":"https:\/\/www.h2kinfosys.com\/blog\/wp-json\/wp\/v2\/posts\/4304\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.h2kinfosys.com\/blog\/wp-json\/wp\/v2\/media\/4323"}],"wp:attachment":[{"href":"https:\/\/www.h2kinfosys.com\/blog\/wp-json\/wp\/v2\/media?parent=4304"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.h2kinfosys.com\/blog\/wp-json\/wp\/v2\/categories?post=4304"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.h2kinfosys.com\/blog\/wp-json\/wp\/v2\/tags?post=4304"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}