上一次实践实现了html form来访问Restlet的PUT和DELETE方法，但返回数据都是string，仅能作为演示使用。本次实践将使各方法返回xml和json格式的数据，方便页面、程序的读取和展示。

[b]1.xml库[/b]
首先是基础的xml数据格式。Restlet的扩展包org.restlet.ext.xml.jar提供各种xml相关类库。包中的抽象类XmlRepresentation作为父类提供接口和方法，但不能创建该父类的实例，而是需要使用SaxRepresentation和DomRepresentation类的实例来执行操作。

将Restlet安装目录\Edition Java EE\2.0.10\lib下的org.restlet.ext.xml.jar包加入Build Path。

[b]2.Resource[/b]
修改com.sunny.restlet.order.CustomersResource类，代码如下：

	@Override	protected Representation get() throws ResourceException {		// TODO Auto-generated method stub		Map customers = orderDao.getAllCustomers();		DomRepresentation representation;		try {			representation = new DomRepresentation();			Document dom = representation.getDocument();			Element all = dom.createElement("customers");			dom.appendChild(all);			for (Object object : customers.entrySet()) {				Entry<String, Customer> entry = (Entry) object;				String id = entry.getKey();				Customer customer = entry.getValue();				Element root = dom.createElement("customer");				root.setAttribute("id", id);				all.appendChild(root);				Element namElement = dom.createElement("name");				namElement.appendChild(dom.createTextNode(customer.getName()));				root.appendChild(namElement);				Element addressElement = dom.createElement("address");				addressElement.appendChild(dom.createTextNode(customer						.getAddress()));				root.appendChild(addressElement);			}			dom.normalizeDocument();			return representation;		} catch (IOException e) {			// TODO Auto-generated catch block			e.printStackTrace();		}		return null;	}	@Override	protected Representation post(Representation entity)			throws ResourceException {		// TODO Auto-generated method stub		Form form = new Form(entity);		String name = form.getFirstValue("name");		String address = form.getFirstValue("address");		Customer customer = new Customer(name, address);		String id = orderDao.addCustomer(customer);		customer = orderDao.getCustomerById(id);		if (customer == null) {			return null;		}		DomRepresentation representation;		try {			representation = new DomRepresentation();			Document dom = representation.getDocument();			Element root = dom.createElement("customer");			root.setAttribute("id", id);			dom.appendChild(root);			Element namElement = dom.createElement("name");			root.appendChild(namElement);			namElement.appendChild(dom.createTextNode(customer.getName()));			Element addressElement = dom.createElement("address");			root.appendChild(addressElement);			addressElement.appendChild(dom					.createTextNode(customer.getAddress()));			dom.normalizeDocument();			return representation;		} catch (IOException e) {			// TODO Auto-generated catch block			e.printStackTrace();		}		return null;	}

类中将/customers资源的get和post方法返回的Representation修改为DomRepresentation，并创建dom文件来格式化数据。

修改com.sunny.restlet.order.CustomerResource类，代码如下：

	@Override	protected Representation delete() throws ResourceException {		// TODO Auto-generated method stub		String customerId = (String) getRequest().getAttributes().get("custId");		orderDao.deleteCustomerById(customerId);		DomRepresentation representation;		try {			representation = new DomRepresentation();			Document dom = representation.getDocument();			Element root = dom.createElement("message");			dom.appendChild(root);			root.appendChild(dom.createTextNode("success"));			dom.normalizeDocument();			return representation;		} catch (IOException e) {			// TODO Auto-generated catch block			e.printStackTrace();		}		return null;	}	@Override	protected Representation get() throws ResourceException {		// TODO Auto-generated method stub		String customerId = (String) getRequest().getAttributes().get("custId");		Customer customer = orderDao.getCustomerById(customerId);		if (customer == null) {			return null;		}		DomRepresentation representation;		try {			representation = new DomRepresentation();			Document dom = representation.getDocument();			Element root = dom.createElement("customer");			root.setAttribute("id", customerId);			dom.appendChild(root);			Element namElement = dom.createElement("name");			root.appendChild(namElement);			namElement.appendChild(dom.createTextNode(customer.getName()));			Element addressElement = dom.createElement("address");			root.appendChild(addressElement);			addressElement.appendChild(dom					.createTextNode(customer.getAddress()));			dom.normalizeDocument();			return representation;		} catch (IOException e) {			// TODO Auto-generated catch block			e.printStackTrace();		}		return null;	}	@Override	protected Representation put(Representation entity)			throws ResourceException {		// TODO Auto-generated method stub		String customerId = (String) getRequest().getAttributes().get("custId");		Form form = new Form(entity);		String name = form.getFirstValue("name");		String address = form.getFirstValue("address");		Customer customer = new Customer(name, address);		orderDao.updateCustomerById(customer, customerId);		customer = orderDao.getCustomerById(customerId);		if (customer == null) {			return null;		}		DomRepresentation representation;		try {			representation = new DomRepresentation();			Document dom = representation.getDocument();			Element root = dom.createElement("customer");			root.setAttribute("id", customerId);			dom.appendChild(root);			Element namElement = dom.createElement("name");			root.appendChild(namElement);			namElement.appendChild(dom.createTextNode(customer.getName()));			Element addressElement = dom.createElement("address");			root.appendChild(addressElement);			addressElement.appendChild(dom					.createTextNode(customer.getAddress()));			dom.normalizeDocument();			return representation;		} catch (IOException e) {			// TODO Auto-generated catch block			e.printStackTrace();		}		return null;	}

类中将/customer/{custId}的资源的get、put和delete方法返回的Representation修改为DomRepresentation，并创建dom文件来格式化数据。

[b]3.测试[/b]
部署程序后，使用浏览器访问[url]http://localhost:8080/firstSteps/[/url]，并将页面上的五个链接在新页面中打开访问。
在post.jsp中输入[name=0, address=0]并提交form，可以看到提示信息
[list]
[*]<?xml version="1.0" encoding="UTF-8"?>
[*] <customer id="0">
[*] <name>0</name>
[*] <address>0</address>
[*] </customer>
[/list]
说明调用post方法访问/customers返回xml数据成功，数据被新增。

再次在post.jsp中输入[name=1, address=1]并提交form，刷新get customers"链接页面，可以看到提示信息
[list]
[*]<?xml version="1.0" encoding="UTF-8"?>
[*] <customers>
[*] <customer id="0">
[*] <name>0</name>
[*] <address>0</address>
[*] </customer>
[*] <customer id="1">
[*] <name>1</name>
[*] <address>1</address>
[*] </customer>
[*] </customers>
[/list]
说明调用get方法访问/customers返回xml数据成功。

在put.jsp中输入[id=0, name=00, address=00]并提交form，可以看到提示信息
[list]
[*]<?xml version="1.0" encoding="UTF-8"?>
[*] <customer id="0">
[*] <name>00</name>
[*] <address>00</address>
[*] </customer>
[/list]
说明调用put方法访问/customer/{custId}返回xml数据成功，数据被修改。

在get.jsp中输入[id=0]并提交form，可以看到提示信息同上。说明调用get方法访问/customer/{custId}返回xml数据成功。

在delete.jsp中输入[id=0]并提交form，可以看到提示信息
[list]
[*]<?xml version="1.0" encoding="UTF-8"?>
[*] <message>success</message>
[/list]
刷新get customers"链接页面，可以看到提示信息
[list]
[*]<?xml version="1.0" encoding="UTF-8"?>
[*] customers>
[*] <customer id="1">
[*] <name>1</name>
[*] <address>1</address>
[*] </customer>
[*] </customers>
[/list]
说明调用delete方法访问/customer/{custId}返回xml数据成功，数据被删除。

[b]4.使用ClientResource测试[/b]
下面我们使用第五节中用到的ClientResource客户端方式调用Restlet服务。
修改com.sunny.restlet.order.CustomerResource类，代码如下：

	public static void main(String[] args) {		// TODO Auto-generated method stub		try {			ClientResource clientCustomers = new ClientResource(					"http://localhost:8080/firstSteps/spring/customers");			ClientResource clientCustomer = new ClientResource(					"http://localhost:8080/firstSteps/spring/customers/0");			Form form = new Form();			form.add("name", "b");			form.add("address", "b");			Representation representation = clientCustomers.post(form);			System.out.println(representation.getText());			representation = clientCustomers.get();			System.out.println(representation.getText());			form.clear();			form.add("name", "c");			form.add("address", "c");			representation = clientCustomer.put(form);			System.out.println(representation.getText());			representation = clientCustomer.get();			System.out.println(representation.getText());			representation = clientCustomer.delete();			System.out.println(representation.getText());			representation = clientCustomers.get();			System.out.println(representation.getText());		} catch (Exception e) {			e.printStackTrace();		}	}

重新部署firstSteps后，运行Test类，在控制台可以看到输出信息
[list]
[*]2013-1-6 16:45:29 org.restlet.engine.http.connector.HttpClientHelper start
[*]信息: Starting the default HTTP client
[*]<?xml version="1.0" encoding="UTF-8"?><customer id="0"><name>b</name><address>b</address></customer>
[*]<?xml version="1.0" encoding="UTF-8"?><customers><customer id="0"><name>b</name><address>b</address></customer></customers>
[*]2013-1-6 16:45:29 org.restlet.engine.http.connector.HttpClientHelper start
[*]信息: Starting the default HTTP client
[*]<?xml version="1.0" encoding="UTF-8"?><customer id="0"><name>c</name><address>c</address></customer>
[*]<?xml version="1.0" encoding="UTF-8"?><customer id="0"><name>c</name><address>c</address></customer>
[*]<?xml version="1.0" encoding="UTF-8"?><message>success</message>
[*]<?xml version="1.0" encoding="UTF-8"?><customers/>
[/list]
说明客户端方式调用成功。

[b]5.json库[/b]
Json作为现在通用的互联网数据传输格式，Restlet当然要支持的了。Restlet的扩展包org.restlet.ext.json.jar提供各种xml相关类库。包中的JsonRepresentation类可以作为返回数据载体使用，其中对多种数据类型提供了支持。

将Restlet安装目录\Edition Java EE\2.0.10\lib下的org.restlet.ext.json.jar包和org.json.jar包加入Build Path。

[b]6.Resource[/b]
修改com.sunny.restlet.order.CustomersResource类，代码如下：

	@Override	protected Representation get() throws ResourceException {		// TODO Auto-generated method stub		Map customers = orderDao.getAllCustomers();		return new JsonRepresentation(customers);	}	@Override	protected Representation post(Representation entity)			throws ResourceException {		// TODO Auto-generated method stub		Form form = new Form(entity);		String name = form.getFirstValue("name");		String address = form.getFirstValue("address");		Customer customer = new Customer(name, address);		String id = orderDao.addCustomer(customer);		customer = orderDao.getCustomerById(id);		if (customer == null) {			return null;		}		return new JsonRepresentation(customer);		}

类中将/customers资源的get和post方法返回的Representation修改为JsonRepresentation。

修改com.sunny.restlet.order.CustomerResource类，代码如下：

	@Override	protected Representation delete() throws ResourceException {		// TODO Auto-generated method stub		String customerId = (String) getRequest().getAttributes().get("custId");		orderDao.deleteCustomerById(customerId);		return new JsonRepresentation("success");	}	@Override	protected Representation get() throws ResourceException {		// TODO Auto-generated method stub		String customerId = (String) getRequest().getAttributes().get("custId");		Customer customer = orderDao.getCustomerById(customerId);		if (customer == null) {			return null;		}		return new JsonRepresentation(customer);	}	@Override	protected Representation put(Representation entity)			throws ResourceException {		// TODO Auto-generated method stub		String customerId = (String) getRequest().getAttributes().get("custId");		Form form = new Form(entity);		String name = form.getFirstValue("name");		String address = form.getFirstValue("address");		Customer customer = new Customer(name, address);		orderDao.updateCustomerById(customer, customerId);		customer = orderDao.getCustomerById(customerId);		if (customer == null) {			return null;		}		return new JsonRepresentation(customer);	}

类中将/customer/{custId}的资源的get、put和delete方法返回的Representation修改为JsonRepresentation。可以看到JsonRepresentation对各数据类型的支持。

[b]7.测试[/b]
重新部署firstSteps后，运行Test类，在控制台可以看到输出信息
[list]
[*]2013-1-6 17:32:20 org.restlet.engine.http.connector.HttpClientHelper start
[*]信息: Starting the default HTTP client
[*]{"address":"b","name":"b"}
[*]{"0":"Customer [name=b, address=b]"}
[*]2013-1-6 17:32:21 org.restlet.engine.http.connector.HttpClientHelper start
[*]信息: Starting the default HTTP client
[*]{"address":"c","name":"c"}
[*]{"address":"c","name":"c"}
[*]success
[*]{}
[/list]
说明客户端方式调用资源，返回json数据成功。

同样可以通过页面来访问修改后的程序，但是返回会是个文件，下载打开后内容和上面的提示信息类似。

[b]8.思考[/b]
我们也可以简单的使用StringRepresentation来达到相同的效果，但是需要自己在代码中调用Dom4J和JSON类库来生成json和xml字符串，再使用StringRepresentation将结果返回。