This chapter describes how to develop Representational State Transfer (RESTful) Web services.
This chapter includes the following sections:
REST describes any simple interface that transmits data over a standardized interface (such as HTTP) without an additional messaging layer, such as Simple Object Access Protocol (SOAP). REST provides a set of design rules for creating stateless services that are viewed as resources, or sources of specific information, and can be identified by their unique URIs. A client accesses the resource using the URI, a standardized fixed set of methods, and a representation of the resource is returned. The client is said to transfer state with each new resource representation.
WebLogic Server supports the following methods to enable the development of RESTful Web services:
Register and use the set of pre-built shared libraries, delivered with WebLogic Server, that are required to run Jersey JAX-RS Reference Implementation (RI). The following versions are available as pre-built shared libraries:
JAX-RS RI Version 1.9
JAX-RS RI Version 1.1.5.1
As required, you can build and deploy a more recent version of the Jersey JAX-RS RI shared libraries. For information about using the Jersey JAX-RS RI shared libraries, see Using the Jersey JAX-RS Reference Implementation.
Use the standard JAX-WS RI to implement a RESTful using the HTTP protocol, as described in Programming Web Services Using XML Over HTTP.
Note:
The Jersey JAX-RS RI provides an open source, production quality Reference Implementation for building RESTful Web services; it is recommended as a best practice over the standard JAX-WS HTTP protocol method.WebLogic Server ships with a set of pre-built shared libraries, packaged as Web applications, that are required to run applications that are based on the Jersey JAX-RS RI. The following versions are supported:
Jersey JAX-RS RI Version 1.9
Jersey JAX-RS RI Version 1.1.5.1
The following sections summarize the Jersey JAX-RS RI shared libraries and the steps to use them, and how to register a more recent version of the Jersey JAX-RS RI.
The shared libraries are located in the following directory: WL_HOME/common/deployable-libraries.
Table 20-1 lists the pre-built shared library that supports Jersey JAX-RS RI Version 1.9 Web services.
Table 20-1 Shared Library for Jersey JAX-RS RI 1.9
| Functionality | Description |
|---|---|
|
|
Table 20-2 summarizes the pre-built shared libraries that support Jersey JAX-RS RI Version 1.1.5.1 Web services, organized by the functionality that they support. The table also indicates whether the shared library is required or optional.
Table 20-2 Shared Libraries for Jersey JAX-RS RI 1.1.5.1
| Functionality | Description | Required? |
|---|---|---|
|
Jersey |
|
Required |
|
JAX-RS API |
|
Required |
|
JSON processing |
|
Optional |
|
JSON processing |
|
Optional |
|
JSON processing |
|
Optional |
|
JSON streaming |
|
Optional |
|
ATOM processing |
|
Optional |
In addition, the following table lists the dependent JARs that are available on WebLogic Server, and not required to be registered as shared libraries.
To use the Jersey JAX-RS RI, perform the following steps:
Register the Jersey JAX-RS RI shared libraries with one or WebLogic Server instances. See Registering the Jersey JAX-RS RI Shared Libraries With Your WebLogic Server Instances.
Configure the Web application that contains the RESTful Web service to use the Jersey JAX-RS RI shared libraries. See Configuring the Web Application to Use the Jersey JAX-RS RI.
Create the JAX-RS Web services and clients. See Creating JAX-RS Web Services and Clients.
As required, you can build and deploy a more recent version of the Jersey JAX-RS RI shared libraries. See Registering a More Recent Version of the Jersey JAX-RS RI.
For more information about the Jersey JAX-RS RI and examples of developing RESTful Web services, see http://jersey.java.net.
Shared Java EE libraries are registered with one or more WebLogic Server instances by deploying them to the target servers and indicating that the deployments are to be shared. Shared Java EE libraries must be targeted to the same WebLogic Server instances you want to deploy applications that reference the libraries.
When a referencing application is deployed, WebLogic Server merges the shared library files with the application. If you try to deploy a referencing application to a server instance that has not registered a required library, deployment of the referencing application fails.
Based on the functionality required by your application and the version of the Jersey JAX-RS RI that you want to use, you can register one or more of the Jersey JAX-RS shared libraries defined in Summary of the Jersey JAX-RS RI Shared Libraries, as follows:
Choose whether you want to use Version 1.9 or 1.1.5.1 of the Jersey JAX-RS RI. Based on the version you choose, refer to Table 20-2 or Table 20-1, respectively, to determine the shared libraries that are required by your application.
Determine the WebLogic Server targets to which you will register the shared libraries. Shared libraries must be registered to the same WebLogic Server instances on which you plan to deploy referencing applications. (You may consider deploying libraries to all servers in a domain, so that you can later deploy referencing applications as needed.)
Register a shared library by deploying the shared library files to the target servers identified in Step 2, and identifying the deployment as a library using the -library option.
The following shows an example of how to deploy the shared libraries that provide support for Jersey JAX-RS RI Version 1.9.
weblogic.Deployer -verbose -noexit -source C:\myinstall\wlserver_10.3\common\deployable-libraries\jersey-bundle-1.9.war -targets myserver -adminurl t3://localhost:7001 -user system -password ******** -deploy -library
If you wish to use Jersey JAX-RS RI Version 1.1.5.1, the following shows an example of how to deploy the shared libraries that provide support for the basic Jersey JAX-RS RI functionality and JAX-RS API.
weblogic.Deployer -verbose -noexit -source C:\myinstall\wlserver_10.3\common\deployable-libraries\jersey-bundle-1.1.5.1.war -targets myserver -adminurl t3://localhost:7001 -user system -password ******** -deploy -library weblogic.Deployer -verbose -noexit -source C:\myinstall\wlserver_10.3\common\deployable-libraries\jsr311-api-1.1.1.war -targets myserver -adminurl t3://localhost:7001 -user system -password ******** -deploy -library
For more information about the weblogic.Deployer, see "weblogic.Deployer Command-Line Reference" in Deploying Applications to Oracle WebLogic Server.
You need to configure the Web application that contains the RESTful Web services to use the Jersey shared libraries. Specifically, you need to update the following two deployment descriptor files that are associated with your application:
web.xml—Update to delegate Web requests to the Jersey servlet. See Updating web.xml to Delegate Web Requests to the Jersey Servlet.
weblogic.xml—Update to reference the shared libraries from Table 20-2 that are required by your application. See Updating weblogic.xml to Reference the Shared Libraries.
Update the web.xml file to delegate all Web requests to the Jersey Servlet, com.sun.jersey.spi.container.servlet.ServletContainer. The web.xml file is located in the WEB-INF directory in the root directory of your application archive.
The following provides an example of how to update the web.xml file:
<web-app>
<servlet>
<display-name>My Jersey Application</display-name>
<servlet-name>MyJerseyApp</servlet-name>
<servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
<init-param>
<param-name>javax.ws.rs.Application</param-name>
<param-value>myPackage.myJerseyApplication</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>MyJerseyApp</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
</web-app>
As shown in the previous example, you need to define the following elements:
<servlet-class> element defines the servlet that is the entry point into the Jersey JAX-RS RI. This value should always be set to com.sun.jersey.spi.container.servlet.ServletContainer.
<init-param> element defines the class that extends the javax.ws.rs.Application.
<servlet-mapping> element defines the base URL pattern that gets mapped to the MyJerseyApp servlet. The portion of the URL after the http://<host>:<port> +<webAppName> is compared to the <url-pattern> by WebLogic Server. If the patterns match, the servlet mapped in this element will be called.
For more information about the web.xml deployment descriptor, see "web.xml Deployment Descriptor Elements" in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server.
Update the weblogic.xml file to reference the shared libraries that are required by your application. The weblogic.xml file is located in the WEB-INF directory in the root directory of your application archive.
The <exact-match> directive enables you to control whether the latest version of the shared libraries that are deployed will be used. If set to true, then the version specified in the weblogic.xml will be used, regardless of whether a newer version has been deployed to WebLogic Server. If set to false, then the latest version deployed to WebLogic Server will be used, regardless of what is specified in the weblogic.xml file.
For example, if you set the <exact-match> directive to false and register as a shared library a more recent version of the Jersey software, as described in Registering a More Recent Version of the Jersey JAX-RS RI, then the more recent version of the shared library will be used by your application automatically; you do not have to edit the weblogic.xml file in this case to pick up the latest version.
The following example shows how to update the weblogic.xml file to use the Jersey JAX-RS RI Version 1.9.
<library-ref>
<library-name>jax-rs</library-name>
<specification-version>1.1</specification-version>
<implementation-version>1.9</implementation-version>
<exact-match>false</exact-match>
</library-ref>
The following example shows how to update the weblogic.xml file to use the Jersey JAX-RS RI Version 1.1.5.1. Not all shared library references will be required for every Web application; the jersey-bundle and jsr311 shared libraries are both required to use the Jersey JAX-RS RI. In this example, <exact-match> is set to false specifying that the latest version of the shared library deployed to WebLogic Server should be used.
<library-ref>
<library-name>jersey-bundle</library-name>
<specification-version>1.1.1</specification-version>
<implementation-version>1.1.5.1</implementation-version>
<exact-match>false</exact-match>
</library-ref>
<library-ref>
<library-name>jsr311</library-name>
<specification-version>1.1.1</specification-version>
<implementation-version>1.1.1</implementation-version>
<exact-match>false</exact-match>
</library-ref>
<library-ref>
<library-name>jackson-core-asl</library-name>
<specification-version>1.0</specification-version>
<implementation-version>1.1.1</implementation-version>
<exact-match>false</exact-match>
</library-ref>
<library-ref>
<library-name>jettison</library-name>
<specification-version>1.1</specification-version>
<implementation-version>1.1</implementation-version>
<exact-match>false</exact-match>
</library-ref>
<library-ref>
<library-name>rome</library-name>
<specification-version>1.0</specification-version>
<implementation-version>1.0</implementation-version>
<exact-match>false</exact-match>
</library-ref>
For more information about the weblogic.xml deployment descriptor, see "weblogic.xml Deployment Descriptor Elements" in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server.
After you have registered the Jersey JAX-RS RI and configured your Web application, you can start creating JAX-RS Web services and clients. The following sections show a simple Web service and client.
For more information about JAX-RS and samples, you might find it helpful to review the Jersey RI documentation at http://wikis.sun.com/display/Jersey/Main.
The following provides a very simple example of a RESTful Web service:
package samples.helloworld;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
// Specifies the path to the RESTful service
@Path("/helloworld")
public class helloWorld {
// Specifies that the method processes HTTP GET requests
@GET
@Path("sayHello")
@Produces("text/plain")
public String sayHello() {
return "Hello World!";
}
}
The following provides a simple RESTful client that calls the RESTful Web service defined previously. This sample uses classes that are provided by the Jersey JAX-RS RI specifically; they are not part of the JAX-RS standard.
package samples.helloworld.client;
import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.WebResource;
public class helloWorldClient {
public helloWorldClient() {
super();
}
public static void main(String[] args) {
Client c = Client.create();
WebResource resource = c.resource("http://localhost:7101/RESTfulService-Project1-context-root/jersey/helloWorld");
String response = resource.get(String.class);
}
}
If you wish to use a more recent version of the Jersey JAX-RS RI shared libraries than the version that is provided with WebLogic Server, you need to perform the following steps:
Download the required version of the relevant Jersey JAR file from the Jersey Web site at: http://jersey.java.net.
Expand the JAR file downloaded in Step 1 and create a new shared library following the steps described in "Creating Shared Java EE Libraries" in Developing Applications for Oracle WebLogic Server.
Register the shared library by deploying the shared library files to the target servers identified in Step 2, and identifying the deployment as a library using the -library option. You must do the following:
Set the -name argument to match the standard Jersey JAX-RS RI shared library name, defined in Table 20-2. For example, jersey-bundle.
Set the -libSpecVer and -libImplVer arguments to distinguish between the different shared library versions.
The following shows an example of how to deploy the latest versions of the Jersey JAX-RS RI functionality. For more information about the weblogic.Deployer, see "weblogic.Deployer Command-Line Reference" in Deploying Applications to Oracle WebLogic Server.
weblogic.Deployer -verbose -noexit -name jersey-bundle -source C:\myinstall\wlserver_10.3\common\deployable-libraries\jersey-bundle-1.2.war -targets myserver -adminurl t3://localhost:7001 -user system -password ******** -deploy -library -libspecver 1.2 -libimplver 1.2
Determine if you need to reconfigure your Web application.
If you set the <exact-match> directive to false in the weblogic.xml file when configuring your Web application, as described in Configuring the Web Application to Use the Jersey JAX-RS RI, then the shared library with the most recent specification version will be used and you do not have to update your Web application configuration.
If you set the <exact-match> directive to true or if you want to use a version of the Jersey JAX-RS RI that is not the most recent version, then you will have to update the weblogic.xml to reference the desired shared library. For more information, see Configuring the Web Application to Use the Jersey JAX-RS RI.
Redeploy any applications that needs to use the newly registered version of the Jersey JAX-RS shared library.
Note:
As a best practice, it is recommended that you use the Jersey JAX-RS RI shared library solution, described in Using the Jersey JAX-RS Reference Implementation. The Jersey JAX-RS RI provides an open source, production quality RI for building RESTful Web services and supports all of the HTTP methods.When using the HTTP protocol to access Web service resources, the resource identifier is the URL of the resource and the standard operation to be performed on that resource is one of the HTTP methods: GET, PUT, DELETE, POST, or HEAD.
Note:
In this JAX-WS implementation, the set of supported HTTP methods is limited to GET and POST. DELETE, PUT, and HEAD are not supported. Any HTTP requests containing these methods will be rejected with a405 Method Not Allowed error.
If the functionality of PUT and DELETE are required, the desired action can be accomplished by tunneling the actual method to be executed on the POST method. This is a workaround referred to as overloaded POST. (A Web search on "REST overloaded POST" will return a number of ways to accomplish this.
You build RESTful-like endpoints using the invoke() method of the javax.xml.ws.Provider<T> interface (see https://download.oracle.com/javaee/5/api/javax/xml/ws/Provider.html). The Provider interface provides a dynamic alternative to building an service endpoint interface (SEI).
The procedure in this section describes how to program and compile the JWS file required to implement Web services using XML over HTTP. The procedure shows how to create the JWS file from scratch; if you want to update an existing JWS file, you can also use this procedure as a guide.
It is assumed that you have set up an Ant-based development environment and that you have a working build.xml file to which you can add targets for running the jwsc Ant task and deploying the Web services. For more information, see Getting Started With JAX-WS Web Services for Oracle WebLogic Server.
Table 20-4 Steps to Program RESTful Web Services
| # |
Step | Description |
|---|---|---|
|
1 |
Create a new JWS file, or update an existing one, that implements the Web service using XML over HTTP. |
Use your favorite IDE or text editor. See Programming Guidelines for the Web Service Using XML Over HTTP. |
|
2 |
Update your |
For example:
<jwsc srcdir="." destdir="output/restEar">
<jws file="NearbyCity.java" type="JAXWS"/>
</jwsc>
For more information, see "Running the jwsc WebLogic Web Services Ant Task" in Getting Started With JAX-WS Web Services for Oracle WebLogic Server. |
|
3 |
Run the Ant target to build the Web service. |
For example: prompt> ant build-rest |
|
4 |
Deploy the Web service as usual. |
See "Deploying and Undeploying WebLogic Web Services" in Getting Started With JAX-WS Web Services for Oracle WebLogic Server. |
|
5 |
Access the Web service from your Web service client. |
The following example shows a simple JWS file that implements a Web service using XML over HTTP; see the explanation after the example for coding guidelines that correspond to the Java code in bold.
package examples.webservices.jaxws.rest; import javax.xml.ws.WebServiceProvider; import javax.xml.ws.BindingType; import javax.xml.ws.Provider; import javax.xml.ws.WebServiceContext; import javax.xml.ws.handler.MessageContext; import javax.xml.ws.http.HTTPBinding; import javax.xml.ws.http.HTTPException; import javax.xml.transform.Source; import javax.xml.transform.stream.StreamSource; import javax.annotation.Resource; import java.io.ByteArrayInputStream; import java.util.StringTokenizer; @WebServiceProvider( targetNamespace="http://example.org", serviceName = "NearbyCityService") @BindingType(value = HTTPBinding.HTTP_BINDING) public class NearbyCity implements Provider<Source> { @Resource(type=Object.class) protected WebServiceContext wsContext; public Source invoke(Source source) { try { MessageContext messageContext = wsContext.getMessageContext(); // Obtain the HTTP mehtod of the input request. javax.servlet.http.HttpServletRequest servletRequest = (javax.servlet.http.HttpServletRequest)messageContext.get( MessageContext.SERVLET_REQUEST); String httpMethod = servletRequest.getMethod(); if (httpMethod.equalsIgnoreCase("GET")); { String query = (String)messageContext.get(MessageContext.QUERY_STRING); if (query != null && query.contains("lat=") && query.contains("long=")) { return createSource(query); } else { System.err.println("Query String = "+query); throw new HTTPException(404); } } catch(Exception e) { e.printStackTrace(); throw new HTTPException(500); } } } else { // This operation only supports "GET" throw new HTTPException405); } private Source createSource(String str) throws Exception { StringTokenizer st = new StringTokenizer(str, "=&/"); String latLong = st.nextToken(); double latitude = Double.parseDouble(st.nextToken()); latLong = st.nextToken(); double longitude = Double.parseDouble(st.nextToken()); City nearby = City.findNearBy(latitude, longitude); String body = nearby.toXML(); return new StreamSource(new ByteArrayInputStream(body.getBytes())); } static class City { String city; String state; double latitude; double longitude; City(String city, double lati, double longi, String st) { this.city = city; this.state = st; this.latitude = lati; this.longitude = longi; } double distance(double lati, double longi) { return Math.sqrt((lati-this.latitude)*(lati-this.latitude) + (longi-this.longitude)*(longi-this.longitude)) ; } static final City[] cities = { new City("San Francisco",37.7749295,-122.4194155,"CA"), new City("Columbus",39.9611755,-82.9987942,"OH"), new City("Indianapolis",39.7683765,-86.1580423,"IN"), new City("Jacksonville",30.3321838,-81.655651,"FL"), new City("San Jose",37.3393857,-121.8949555,"CA"), new City("Detroit",42.331427,-83.0457538,"MI"), new City("Dallas",32.7830556,-96.8066667,"TX"), new City("San Diego",32.7153292,-117.1572551,"CA"), new City("San Antonio",29.4241219,-98.4936282,"TX"), new City("Phoenix",33.4483771,-112.0740373,"AZ"), new City("Philadelphia",39.952335,-75.163789,"PA"), new City("Houston",29.7632836,-95.3632715,"TX"), new City("Chicago",41.850033,-87.6500523,"IL"), new City("Los Angeles",34.0522342,-118.2436849,"CA"), new City("New York",40.7142691,-74.0059729,"NY")}; static City findNearBy(double lati, double longi) { int n = 0; for (int i = 1; i < cities.length; i++) { if (cities[i].distance(lati, longi) < cities[n].distance(lati, longi)) { n = i; } } return cities[n]; } public String toXML() { return "<ns:NearbyCity xmlns:ns=\"http://example.org\"><City>" +this.city+"</City><State>"+ this.state+"</State><Lat>" +this.latitude + "</Lat><Lng>"+this.longitude+"</Lng></ns:NearbyCity>"; } } }
Follow these guidelines when programming the JWS file that implements the Web service using XML over HTTP. Code snippets of the guidelines are shown in bold in the preceding example.
Import the packages required to implement the Provider Web service.
import javax.xml.ws.WebServiceProvider; import javax.xml.ws.BindingType; import javax.xml.ws.Provider;
Annotate the Provider implementation class and set the binding type to HTTP.
@WebServiceProvider( targetNamespace="http://example.org", serviceName = "NearbyCityService") @BindingType(value = HTTPBinding.HTTP_BINDING)
Implement the invoke() method of the Provider interface.
public class NearbyCity implements Provider<Source> {
@Resource(type=Object.class)
protected WebServiceContext wsContext;
public Source invoke(Source source) {
...
}
Get the request string using the QUERY_STRING field in the javax.xml.ws.handler.MessageContext for processing (see message URL https://download.oracle.com/javaee/5/api/javax/xml/ws/handler/MessageContext.html). The query string is then passed to the createSource() method that returns the city, state, longitude, and latitude that is closest to the specified values.
String query =
(String)messageContext.get(MessageContext.QUERY_STRING);
.
.
.
return createSource(query);
To access the Web service from a Web service client, use the resource URI. For example:
URL url = new URL (http://localhost:7001/NearbyCity/NearbyCityService?lat=35&long=-120);
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
connection.setRequestMethod("POST");
// Get result
InputStream is = connection.getInputStream();
In this example, you set the latitude (lat) and longitude (long) values, as required, to access the required resource.
You can secure Web services that use XML over HTTP using the same methods that you use to secure Web applications. For more information, see "Options for Securing Web Application and EJB Resources" in Securing Resources Using Roles and Policies for Oracle WebLogic Server.