Java: Restful Service

What is a Web service?

Web service is any piece of software that makes itself available over the Internet and uses a standardized XML messaging system. Client invokes a Web service by sending an XML message, then waits for a corresponding XML response. Because all communication is in XML, Web services are not tied to any one operating system or programming language

What UDDI means?

UDDI stands for Universal, Description, Discovery, and Integration. It is the discovery layer in the web services protocol stack.

What is REST?

REST stands for Representational State Transfer

REST vs SOAP

The RESTFul web services are simple to implement and test. It supports various data formats such as XML, JSON etc.

Rest is light weight.

Not just xml, it will support json,html,java script

REST has no WSDL interface definition

REST is over HTTP, but SOAP can be over any transport protocols such HTTP, FTP, STMP, JMS etc.

SOAP is using soap envelope, but REST is just XML.

REST is stateless. REST services are easily cacheable.

REST has the support for sending parameters to the method/resource that gets invoked in the existing query parameters style like
example.com/users/user1/address

WS-Security which adds some enterprise security features in SOAP

Sample WADL

</representation>

</request>

</response>

</method>

</resource>

Service/Provider Class

@Singleton

@Path("officeservice")

public class HRBColsService {

@POST

@Produces(Constants.JSONRESP)

@Consumes(MediaType.APPLICATION_JSON)

@Path("{applicationName}/{templateID}"+Constants.RAW_DATA_URI+"/getOfficeDetailsByAddress/")

public MapResponse getOfficeDetailsByAddress(@PathParam("applicationName") String applicationName,

@PathParam("templateID") String templateID, @FormParam("mreq") String txtRequest){

….

}

@GET

@Produces(Constants.JAVASCRIPTRESP)

@Path("{applicationName}/{templateID}"+Constants.JSONP_URI+"/getOfficeDetailsByQuery/")

public String getOfficeDetailsByQuery(@PathParam("applicationName") String applicationName,

@PathParam("templateID") String templateID,@QueryParam("query") String query,@QueryParam("callback") String callback

) {

return callback+"("+jsonString+");";

}

Web.xml

<display-name>JAX-RS REST Servlet</display-name>

<servlet-name>services</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.test.services.gmap</param-value>

</init-param>

<load-on-startup>1</load-on-startup>

</servlet>

<servlet-mapping>

<servlet-name>services</servlet-name>

<url-pattern>/*</url-pattern>

</servlet-mapping>

jersey will consider all the classes which are under the package com.test.services.gmap

How to expose one service implementation as Restful and webservice?
Create a normal web application in eclipse and use the below files. I assume you are aware of pom.xml

package com.sudheer.cxf.demo.servImpl;

import javax.ws.rs.Consumes;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;

import org.springframework.util.StringUtils;

import com.example.employeeservice.Employee;
import com.example.employeeservice.EmployeeService;
import com.example.employeeservice.NoSuchEmployeeException;
import com.javatch.cxf.dao.utils.EmployeeUtils;

@Path("/")

public class EmployeeServiceImpl implements EmployeeService{

@GET
@Path("/getemployee/{name}/")
@Produces(value = {"application/json" })
public Employee getEmployeesByName(@PathParam("name") String name)
throws NoSuchEmployeeException {
if(EmployeeUtils.employees.containsKey(name)) {
return EmployeeUtils.employees.get(name);
} else {
throw new NoSuchEmployeeException("Employee " + name + "doesn't exists");
}

}

@POST
@Path("/addemployee/")
@Consumes(value="application/json")
@Produces(value = {"application/json" })
public void addEmployee(Employee employee) {
if(StringUtils.hasText(employee.getName())){
EmployeeUtils.employees.put(employee.getName(), employee);
} else {
System.out.println("Invalid Employee object");
}

}

}

package com.sudheer.test.client;

import java.io.BufferedInputStream;

import java.io.ByteArrayOutputStream;

import java.io.InputStream;

import java.net.MalformedURLException;

import java.net.URL;

public class RestClient {

public static void main(String[] args) {

System.out.println("Sent HTTP GET request to query customer info");

URL url;

try {

url = new URL("http://localhost:8080/cxfpoc/employeeservice/getemployee/Ryan");

getStringFromIOStream(url);

} catch (MalformedURLException e1) {

// TODO Auto-generated catch block

e1.printStackTrace();

}

private static void getStringFromIOStream(URL url) {

try {

InputStream in = url.openStream();

BufferedInputStream bis = new BufferedInputStream(in);

ByteArrayOutputStream buf = new ByteArrayOutputStream();

int result = bis.read();

while(result != -1) {

byte b = (byte)result;

buf.write(b);

result = bis.read();

}

System.out.println(buf.toString());

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

package com.sudheer.test.client;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.example.employeeservice.Employee;

import com.example.employeeservice.EmployeeService;

import com.example.employeeservice.NoSuchEmployeeException;

public class SoapClient {

/**

* @param args

public static void main(String[] args) {

// TODO Auto-generated method stub

ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[]

{"/client-beans.xml"});

EmployeeService client = (EmployeeService) context.

getBean("orderClient");

// Populate the Order bean

Employee employee;

try {

employee = client.getEmployeesByName("Ryan");

System.out.println("Employee Name : "+employee.getName());

} catch (NoSuchEmployeeException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

client-bean.xml

This will be used in SoapClient java

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns:jaxws="http://cxf.apache.org/jaxws"

xsi:schemaLocation="

http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans.xsd

http://cxf.apache.org/jaxws http://cxf.apache.org/schemas/jaxws.xsd">

<jaxws:client id="orderClient" serviceClass=

"com.example.employeeservice.EmployeeService" address=

"http://localhost:8080/cxfpoc/EmployeeService" />

</beans>

cxfbeans.xml

Used to expose Restful and webservice

<?xml version="1.0" encoding="UTF-8"?>

<!-- Licensed to the Apache Software Foundation (ASF) under one or more contributor

license agreements. See the NOTICE file distributed with this work for additional

information regarding copyright ownership. The ASF licenses this file to

you under the Apache License, Version 2.0 (the "License"); you may not use

this file except in compliance with the License. You may obtain a copy of

the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required

by applicable law or agreed to in writing, software distributed under the

License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS

OF ANY KIND, either express or implied. See the License for the specific

language governing permissions and limitations under the License. -->

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xmlns:aop="http://www.springframework.org/schema/aop"

xmlns:jaxws="http://cxf.apache.org/jaxws"

xmlns:jaxrs="http://cxf.apache.org/jaxrs"

xsi:schemaLocation="

http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd

http://cxf.apache.org/jaxws http://cxf.apache.org/schemas/jaxws.xsd

http://cxf.apache.org/jaxrs http://cxf.apache.org/schemas/jaxrs.xsd

http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-3.0.xsd" >

<jaxrs:server id="EmployeeServiceRS" address="/employeeservice" >

<jaxrs:serviceBeans>

</jaxrs:serviceBeans>

<jaxrs:providers>

</jaxrs:providers>

</jaxrs:server>

<jaxws:endpoint id="EmployeeService"

implementor="#employeeServicesRS" address="/EmployeeService" />

<aop:config>

<aop:aspect ref="beforeAndAfterLogging">

<aop:pointcut expression="within(com.hrblock.cxf.demo.servImpl.*)" id="before-method" />

<aop:before method="beforeMethod" pointcut-ref="before-method" />

</aop:aspect>

<aop:aspect ref="beforeAndAfterLogging">

<aop:pointcut expression="within(com.hrblock.cxf.demo.servImpl.*)" id="after-method" />

<aop:after method="afterMethod" pointcut-ref="after-method" />

</aop:aspect>

</aop:config>

</bean>

</beans>

web.xml

<!DOCTYPE web-app PUBLIC

"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"

"http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>

<display-name>Archetype Created Web Application</display-name>

<context-param>

<param-name>contextConfigLocation</param-name>

<param-value>WEB-INF/cxfbeans.xml</param-value>

</context-param>

<listener-class>

org.springframework.web.context.ContextLoaderListener

</listener-class>

</listener>

<servlet-name>CXFServlet</servlet-name>

<display-name>CXF Servlet</display-name>

<servlet-class>

org.apache.cxf.transport.servlet.CXFServlet

</servlet-class>

<load-on-startup>1</load-on-startup>

</servlet>

<servlet-mapping>

<servlet-name>CXFServlet</servlet-name>

<url-pattern>/*</url-pattern>

</servlet-mapping>

</web-app>

pom.xml

<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">

<groupId>com.javatch.cxf</groupId>

<artifactId>cxfpoc</artifactId>

<name>com.javatch.cxf Maven Webapp</name>

<url>http://maven.apache.org</url>

<cxf.version>2.5.1</cxf.version>

</properties>

<groupId>junit</groupId>

<artifactId>junit</artifactId>

</dependency>

<groupId>org.apache.cxf</groupId>

<artifactId>cxf-rt-frontend-jaxws</artifactId>

<version>${cxf.version}</version>

</dependency>

<groupId>org.apache.cxf</groupId>

<artifactId>cxf-rt-frontend-jaxrs</artifactId>

<version>${cxf.version}</version>

</dependency>

<groupId>aspectj</groupId>

<artifactId>aspectjrt</artifactId>

</dependency>

<groupId>org.aspectj</groupId>

<artifactId>aspectjweaver</artifactId>

</dependency>

<groupId>org.codehaus.jackson</groupId>

<artifactId>jackson-jaxrs</artifactId>

</dependency>

</dependencies>

<build>

<defaultGoal>install</defaultGoal>

<directory>src/main/resources/wsdl</directory>

</resource>

<directory>src/main/resources</directory>

</resource>

</resources>

<artifactId>maven-war-plugin</artifactId>

<directory>src/main/resources/wsdl</directory>

</includes>

</resource>

<directory>src/main/resources</directory>

</includes>

</resource>

</webResources>

</configuration>

</plugin>

<artifactId>maven-compiler-plugin</artifactId>

</configuration>

</plugin>

</plugins>

</pluginManagement>

<groupId>org.apache.cxf</groupId>

<artifactId>cxf-codegen-plugin</artifactId>

<version>${cxf.version}</version>

<id>generate-sources</id>

<phase>generate-sources</phase>

<sourceRoot>${basedir}/target/generated/cxf</sourceRoot>

<wsdl>src/main/resources/wsdl/EmployeeService.wsdl</wsdl>

<!-- <bindingFiles> <bindingFile>${basedir}/wsdl/binding.xml</bindingFile>

</bindingFiles> -->

</wsdlOption>

</wsdlOptions>

</configuration>

<goals>

</goals>

</execution>

</executions>

</plugin>

</plugins>

</build>

</project>

Service listings and WADL queries

Links to WADL instances for RESTful endpoints are available from {base endpointaddress}/services, in addition to SOAP endpoints if any.
Base address : 'http://localhost:8080'
WAR name : 'restpoc'
CXFServlet : '/books/*'
jaxrs:server/@address = '/getemployee'
and visiting

http://localhost:8080/restpoc/books
http://localhost:8080/restpoc/books/services

will let you see all the WADL links.

Going to the service listings page is not the only way to see WADL instances, one can also get it using a ?_wadl query.

http://localhost:8080/restpoc/books/getemployee?_wadl

will give you the description of all the root resource classes registered
with a given jaxrs:server endpoint.

For example, if the following 2 root resource classes has been registered with this endpoint:

@Path("/fiction")
public class FictionBookgetemployee {
}
@Path("/sport")
public class SportBookgetemployee {
}
then WADL will contain the description of both FictionBookgetemployee and SportBookgetemployee resources.

> http://localhost:8080/restpoc/books/getemployee/fiction?_wadl
> http://localhost:8080/restpoc/books/getemployee/sport?_wadl

Service listings and WADL queries - Jersey

To get the WADL from Jersey

WAR NAME - Jersey-Sample
Jersey Servlet Mapping - /*

http://localhost:8080/Jersey-Sample/application.wadl

Use this URL to call the below service
http://localhost:8080/Jersey-Sample/getemployee/sdheer/32

@Path("/")
public class EmployeeServiceImpl{

@Path("/getemployee/{name}/{name}")
@Produces(value = {"application/json" })
public Employee getEmployeesByName(@PathParam("name") String name,@PathParam("age") int age)

Use this URL to call the below service

@Path("/")
public class EmployeeServiceImpl{
http://localhost:8080/Jersey-Sample/
@GET
@Produces(value = {"application/json" })
public Employee getEmployeesByName()

You cannot have two different services like below without proper path

@GET
@Produces(value = {"application/json" })
public Employee getEmployeesByName(){
}

@GET
@Produces(value = {"application/json" })
public Employee anotherMethod(){
}

Error, A message body writer for Java type, class com.jersey.demo.beans.Employee, and MIME media type, application/json, was not found

Add @XmlRootElement top of the bean class Employee

A Complete Simple Jersey Rest Service Example

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" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>Jersey Sample</display-name>

<servlet>
<display-name>JAX-RS REST Servlet</display-name>
<servlet-name>services</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.jersey.demo.servImpl</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>services</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>
</web-app>

package com.jersey.demo.servImpl;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;

import com.jersey.demo.beans.Employee;

@Path("/")

public class EmployeeServiceImpl{

@GET
@Path("/getemployee/{name}/{name}")
@Produces(value = {"application/json" })
public Employee getEmployeesByName(){
Employee employee = new Employee();
employee.setName("name");
employee.setAge(123);
return employee;
}
}

package com.jersey.demo.beans;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Employee {

private String name;
private int age;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}

Java

Thursday, December 13, 2012

Restful Service

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