使用Spring MVC发布Restful资源不难，读写Mongodb也不难，但是能不能让两者无缝地对接起来呢？也就是说，让Spring MVC来做retrieve/stringify的工作，我们的方法就像这样：
public DBObject createModel(@RequestBody DBObject model)
按照Spring文档的说法，当一个@RequestMapping的方法没有@ResponesBody时，Spring会尝试渲染View；如果方法同时也带了@ResponseBody，Spring会查找当前已经注册的HttpMessageConverter,通过这些Converter得到希望的结果。所以，我们要做的第一步就是实现DBObject的Converter：
package com.narcissu5.util; import com.mongodb.BasicDBObject; import com.mongodb.DBObject; import com.mongodb.util.JSON; import org.springframework.http.HttpInputMessage; import org.springframework.http.HttpOutputMessage; import org.springframework.http.MediaType; import org.springframework.http.converter.HttpMessageConverter; import org.springframework.http.converter.HttpMessageNotReadableException; import org.springframework.http.converter.HttpMessageNotWritableException; import java.io.*; import java.util.ArrayList; import java.util.List; /** * Created by Narcissu5 on 2014/4/5. */ public class DBObjectMessageConverter implements HttpMessageConverter<DBObject> { @Override public boolean canRead(Class<?> aClass, MediaType mediaType) { if (DBObject.class.isAssignableFrom(aClass)) { return true; } else { return false; } } @Override public boolean canWrite(Class<?> aClass, MediaType mediaType) { if (DBObject.class.isAssignableFrom(aClass)) { return true; } else { return false; } } @Override public List<MediaType> getSupportedMediaTypes() { List<MediaType> supports = new ArrayList<MediaType>(); supports.add(MediaType.APPLICATION_JSON); return supports; } @Override public DBObject read(Class<? extends DBObject> aClass, HttpInputMessage httpInputMessage) throws IOException, HttpMessageNotReadableException { Object object = JSON.parse(readToEnd(httpInputMessage.getBody())); if (object == null) { return new BasicDBObject(); } else { return (DBObject) object; } } @Override public void write(DBObject dbObject, MediaType mediaType, HttpOutputMessage httpOutputMessage) throws IOException, HttpMessageNotWritableException { httpOutputMessage.getBody().write(dbObject.toString().getBytes()); } protected String readToEnd(InputStream is) throws IOException { java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A"); return s.hasNext() ? s.next() : ""; } }
然后需要需要将我们的Converter注册到Spring的Context中去，官方的注册方法是这样：
<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"> <property name="messageConverters"> <util:list id="beanList"> <ref bean="stringHttpMessageConverter"/> <ref bean="marshallingHttpMessageConverter"/> </util:list> </property </bean> <bean id="stringHttpMessageConverter" class="org.springframework.http.converter.StringHttpMessageConverter"/> <bean id="marshallingHttpMessageConverter" class="org.springframework.http.converter.xml.MarshallingHttpMessageConverter"> <property name="marshaller" ref="castorMarshaller" /> <property name="unmarshaller" ref="castorMarshaller" /> </bean> <bean id="castorMarshaller" class="org.springframework.oxm.castor.CastorMarshaller"/>
但是。。。。不起作用，还是*靠谱，实际上应该这样注册：
<mvc:annotation-driven> <mvc:message-converters register-defaults="true"> <bean class="com.narcissu5.util.DBObjectMessageConverter"/> </mvc:message-converters> </mvc:annotation-driven>
register-defaults表示同时也注册默认的Converter，spring内置了几种Converter：
-
ByteArrayHttpMessageConverterconverts byte arrays. -
StringHttpMessageConverterconverts strings. -
FormHttpMessageConverterconverts form data to/from a MultiValueMap<String, String>. -
SourceHttpMessageConverterconverts to/from a javax.xml.transform.Source.
然后是Controller，因为有Converter的帮助，我们不用再费心处理json转换的工作了：
package com.narcissu5.mvc; import com.mongodb.*; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.*; import javax.servlet.http.HttpServletResponse; import java.net.UnknownHostException; /** * Created by Narcissu5 on 2014/4/6. */ @Controller @RequestMapping(value = "/models") public class ModelController { @ResponseBody @RequestMapping(method = RequestMethod.POST) public DBObject createModel(@RequestBody DBObject model) throws UnknownHostException { MongoClient client = new MongoClient("localhost"); DBCollection colModels = client.getDB("MyDB").getCollection("models"); colModels.insert(model); return model; } @ResponseBody @RequestMapping(method = RequestMethod.PUT) public DBObject updateModel(@RequestBody DBObject model) throws UnknownHostException { MongoClient client = new MongoClient("localhost"); DBCollection colModels = client.getDB("MyDB").getCollection("models"); colModels.save(model); return model; } @ResponseBody @RequestMapping(method = RequestMethod.GET) public DBObject queryModel() throws UnknownHostException { MongoClient client = new MongoClient("localhost"); DBCollection colModels = client.getDB("MyDB").getCollection("models"); DBCursor cursor = colModels.find(); BasicDBList all = new BasicDBList(); try { while (cursor.hasNext()) { all.add(cursor.next()); } } finally { cursor.close(); } return all; } @ResponseBody @RequestMapping(method = RequestMethod.PATCH) public DBObject getModel(@RequestBody DBObject query) throws UnknownHostException { MongoClient client = new MongoClient("localhost"); DBCollection colModels = client.getDB("MyDB").getCollection("models"); return colModels.findOne(query); } @RequestMapping(method = RequestMethod.DELETE) public void deleteModel(@RequestBody DBObject std, HttpServletResponse resp) throws UnknownHostException { MongoClient client = new MongoClient("localhost"); DBCollection colModels = client.getDB("MyDB").getCollection("models"); WriteResult result = colModels.remove(std); if (result.getN() > 0) { resp.setStatus(HttpServletResponse.SC_OK); } else { resp.setStatus(HttpServletResponse.SC_NO_CONTENT); } } }
注意这里的查找和删除不像一般的Restful使用/models/{id}这样的路径，这是因为在mongodb中。默认的id是对象而非整型，而且官方也不鼓励使用别的主键类型，因此我们通过消息体将包含主键的对象提交上来，相应的查找的方法也从GET换成了PATCH。
最后是测试，使用Powershell：
function Assert($expression,$message){ Write-Host $message -NoNewline if($expression){ Write-Host "`tSuccess" -ForegroundColor Green } else { Write-Host "`tFail" -ForegroundColor Red } } $url = "http://localhost:8080/models" #POST /models $exception = $false $body = ConvertTo-Json @{name=[GUID]::NewGuid().ToString()} try{ $resp = Invoke-WebRequest -Body $body -ContentType "application/json" -Method Post -Uri $url #-Headers $headers } catch { $exception = $true } Assert (-not $exception -and ($resp.StatusCode -eq 200)) "POST /models" #PUT models $exception = $false $ret = ConvertFrom-Json ([System.Text.Encoding]::UTF8.GetString($resp.Content)) $ret.name = [DateTime]::Now.ToString() $body = ConvertTo-Json $ret try{ $resp = Invoke-WebRequest -Body $body -ContentType "application/json" -Method PUT -Uri $url } catch { $exception = $true } Assert (-not $exception -and ($resp.StatusCode -eq 200)) "PUT /models" #GET /models $exception = $false try{ $resp = Invoke-WebRequest -Method GET -Uri $url } catch { $exception = $true } $ret = ConvertFrom-Json ([System.Text.Encoding]::UTF8.GetString($resp.Content)) Assert (-not $exception -and ($ret.Count -gt 0) -and ($resp.StatusCode -eq 200)) "GET /models" #GET /models $exception = $false $body = ConvertTo-Json (@{_id=$ret[0]._id}) try{ $resp = Invoke-WebRequest -Body $body -Method PATCH -Uri $url } catch { $exception = $true } Assert (-not $exception -and ($resp.StatusCode -eq 200)) "PATCH /models" #DELETE /models $exception = $false try{ $resp = Invoke-WebRequest -Body $body -Method DELETE -Uri $url } catch { $exception = $true } Assert (-not $exception -and ($resp.StatusCode -eq 200)) "DELETE /models"