android使用JSON进行网络数据交换电子版本

1、Good is good, but better carries it.精益求精，善益求善。android使用JSON进行网络数据交换-使用JSON进行网络数据交换网络编程,2009-12-1817:29:44标签:在开发客户端与服务端的应用当中，数据交换接口通常都是通过XML格式来进行数据交换的。近年来，随着AJAX技术的兴起，JSON作为一种轻量级的数据交换格式，以其易于阅读和编写的优点，也越来越多的被使用到各个项目中。在AndroidSDK中，也提供了JSON的类库方便对JSON格式的数据进行处理。本文将快速讲解JSON格式，并通过代码示例演示如何分别在客户端和服务器端进行JSON格式数

2、据的处理。什么是JSONJSON（JavaScriptObjectNotation）是一种轻量级的数据交换格式，易于阅读和编写，同时也易于机器解析和生成，非常适合于服务器与客户端的交互。JSON采用与编程语言无关的文本格式，但是也使用了类C语言的习惯，这些特性使JSON成为理想的数据交换格式。和XML一样，JSON也是基于纯文本的数据格式。由于JSON天生是为JavaScript准备的，因此，JSON的数据格式非常简单，您可以用JSON传输一个简单的String，Number，Boolean，也可以传输一个数组，或者一个复杂的Object对象。String，Number和Boolean用JSO

3、N表示非常简单。例如，用JSON表示一个简单的字符串“abc”，其格式为：abc。除了字符，/和一些控制符（b，f，n，r，t）需要编码外，其他Unicode字符可以直接输出。下图是一个String的完整表示结构：图1.String的完整表示结构一个Number可以根据整型或浮点数表示如下：图2.Number的表示结构这与绝大多数编程语言的表示方法一致，例如：12345（整数）-3.9e10（浮点数）Boolean类型表示为true或false。此外，JavaScript中的null被表示为null，注意，true、false和null都没有双引号，否则将被视为一个String。JSON还可以

4、表示一个数组对象，使用包含所有元素，每个元素用逗号分隔，元素可以是任意的Value，例如，以下数组包含了一个String，Number，Boolean和一个null：HYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9viewplainHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9copytoclipboardHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC

5、65C50F7FA73B558E9printHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9?abc,12345,false,nullabc,12345,false,nullObject对象在JSON中是用包含一系列无序的Key-Value键值对表示的，实际上此处的Object相当于Java中的Map，而不是Java的Class。注意Key只能用String表示。例如，一个Address对象包含如下Key-Value：city:Beijingstreet:ChaoyangRoadpostcode:100

6、025（整数）用JSON表示如下：HYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9viewplainHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9copytoclipboardHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9printHYPERLINK/article/show/129;jsessionid=B5B61D

7、9FD03EDDC65C50F7FA73B558E9?city:Beijing,street:ChaoyangRoad,postcode:100025city:Beijing,street:ChaoyangRoad,postcode:100025其中Value也可以是另一个Object或者数组，因此，复杂的Object可以嵌套表示，例如，一个Person对象包含name和address对象，可以表示如下：HYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9viewplainHYPERLINK/article

8、/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9copytoclipboardHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9printHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9?name:Michael,address:city:Beijing,street:ChaoyangRoad,postcode:100025name:Michael,addr

9、ess:city:Beijing,street:ChaoyangRoad,postcode:100025一个实际例子接下来，我会通过一个例子来详细说明Android客户端程序如何访问服务端的接口程序读取用户列表数据，并在模拟器上显示用户列表数据。1、服务端接口程序首先，我们创建一个名为User的JavaBean作为用户对象类，用来保存演示数据。HYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9viewplainHYPERLINK/article/show/129;jsessionid=B5B61D9FD0

10、3EDDC65C50F7FA73B558E9copytoclipboardHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9printHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9?publicclassUserprivateintid;privateStringname;privateStringemail;privateStringgender;publicintgetId()returnid;publicv

11、oidsetId(intid)this.id=id;publicStringgetName()returnname;publicvoidsetName(Stringname)=name;publicStringgetEmail()returnemail;publicvoidsetEmail(Stringemail)this.email=email;publicStringgetGender()returngender;publicvoidsetGender(Stringgender)this.gender=gender;publicclassUserprivateintid;privateSt

12、ringname;privateStringemail;privateStringgender;publicintgetId()returnid;publicvoidsetId(intid)this.id=id;publicStringgetName()returnname;publicvoidsetName(Stringname)=name;publicStringgetEmail()returnemail;publicvoidsetEmail(Stringemail)this.email=email;publicStringgetGender()returngender;publicvoi

13、dsetGender(Stringgender)this.gender=gender;接下来，我们创建一个名为JSONDemoServlet的Servlet类来作为服务端的接口程序。在这个程序里，定义了一个List对象用来保存用户列表。HYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9viewplainHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9copytoclipboardHYPERLINK/article/

14、show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9printHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9?privateListlist;privateListlist;客户端程序访问服务器端接口时，接口通过prepareData方法为用户列表初始化数据，添加用户数据到List对象中。HYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9viewplainHYP

15、ERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9copytoclipboardHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9printHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9?privatevoidprepareData()list=newArrayList();Userbean1=newUser();bean1.se

16、tId(1001);bean1.setName(Tony);bean1.setEmail(tony);bean1.setGender(male);list.add(bean1);privatevoidprepareData()list=newArrayList();Userbean1=newUser();bean1.setId(1001);bean1.setName(Tony);bean1.setEmail(tony);bean1.setGender(male);list.add(bean1);接着遍历用户列表，把列表中的每个Java用户对象转换为JSONObject对象，再加入到JSONAr

17、ray中去。HYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9viewplainHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9copytoclipboardHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9printHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65

18、C50F7FA73B558E9?JSONArrayarray=newJSONArray();for(Userbean:list)/单个用户JSON对象JSONObjectobj=newJSONObject();tryobj.put(id,bean.getId();obj.put(name,bean.getName();obj.put(email,bean.getEmail();obj.put(gender,bean.getGender();catch(Exceptione)array.put(obj);JSONArrayarray=newJSONArray();for(Userbean:lis

19、t)/单个用户JSON对象JSONObjectobj=newJSONObject();tryobj.put(id,bean.getId();obj.put(name,bean.getName();obj.put(email,bean.getEmail();obj.put(gender,bean.getGender();catch(Exceptione)array.put(obj);最后，通过Servlet输出JSON时，需要设置正确的MIME类型和字符编码。假定服务器使用UTF-8编码，则可以使用以下代码输出编码后的JSON文本：HYPERLINK/article/show/129;jsess

20、ionid=B5B61D9FD03EDDC65C50F7FA73B558E9viewplainHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9copytoclipboardHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9printHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9?response.setContentTyp

21、e(text/plain);response.setCharacterEncoding(UTF-8);PrintWriterout=response.getWriter();out.write(array.toString();out.flush();out.close();JSONDemoServlet.java的完整代码如下：importjava.io.IOException;importjava.io.PrintWriter;importjava.util.ArrayList;importjava.util.List;importjavax.servlet.ServletExceptio

22、n;importjavax.servlet.http.HttpServlet;importjavax.servlet.http.HttpServletRequest;importjavax.servlet.http.HttpServletResponse;importorg.json.JSONArray;importorg.json.JSONObject;publicclassJSONDemoServletextendsHttpServletprivatestaticfinallongserialVersionUID=-7368225680407826408L;privateListlist;

23、/*处理post方式提交的数据*/publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOExceptiondoGet(request,response);/*出来get方式提交的数据*/publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOExceptionresponse.setContentType(text/plain

24、);response.setCharacterEncoding(UTF-8);PrintWriterout=response.getWriter();/准备用户数据prepareData();/JSON数组JSONArrayarray=newJSONArray();for(Userbean:list)/单个用户JSON对象JSONObjectobj=newJSONObject();tryobj.put(id,bean.getId();obj.put(name,bean.getName();obj.put(email,bean.getEmail();obj.put(gender,bean.get

25、Gender();catch(Exceptione)array.put(obj);/输出out.write(array.toString();out.flush();out.close();privatevoidprepareData()list=newArrayList();Userbean1=newUser();bean1.setId(1001);bean1.setName(Tony);bean1.setEmail(tony);bean1.setGender(male);list.add(bean1);Userbean2=newUser();bean2.setId(1002);bean2.

26、setName(Jack);bean2.setEmail(jack);bean2.setGender(male);list.add(bean2);Userbean3=newUser();bean3.setId(1003);bean3.setName(Marry);bean3.setEmail();bean3.setGender(female);list.add(bean3);Userbean4=newUser();bean4.setId(1004);bean4.setName(Linda);bean4.setEmail(linda21);bean4.setGender(female);list

27、.add(bean4);response.setContentType(text/plain);response.setCharacterEncoding(UTF-8);PrintWriterout=response.getWriter();out.write(array.toString();out.flush();out.close();JSONDemoServlet.java的完整代码如下：importjava.io.IOException;importjava.io.PrintWriter;importjava.util.ArrayList;importjava.util.List;i

28、mportjavax.servlet.ServletException;importjavax.servlet.http.HttpServlet;importjavax.servlet.http.HttpServletRequest;importjavax.servlet.http.HttpServletResponse;importorg.json.JSONArray;importorg.json.JSONObject;publicclassJSONDemoServletextendsHttpServletprivatestaticfinallongserialVersionUID=-736

29、8225680407826408L;privateListlist;/*处理post方式提交的数据*/publicvoiddoPost(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOExceptiondoGet(request,response);/*出来get方式提交的数据*/publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException

30、response.setContentType(text/plain);response.setCharacterEncoding(UTF-8);PrintWriterout=response.getWriter();/准备用户数据prepareData();/JSON数组JSONArrayarray=newJSONArray();for(Userbean:list)/单个用户JSON对象JSONObjectobj=newJSONObject();tryobj.put(id,bean.getId();obj.put(name,bean.getName();obj.put(email,bean.

31、getEmail();obj.put(gender,bean.getGender();catch(Exceptione)array.put(obj);/输出out.write(array.toString();out.flush();out.close();privatevoidprepareData()list=newArrayList();Userbean1=newUser();bean1.setId(1001);bean1.setName(Tony);bean1.setEmail(tony);bean1.setGender(male);list.add(bean1);Userbean2=

32、newUser();bean2.setId(1002);bean2.setName(Jack);bean2.setEmail(jack);bean2.setGender(male);list.add(bean2);Userbean3=newUser();bean3.setId(1003);bean3.setName(Marry);bean3.setEmail();bean3.setGender(female);list.add(bean3);Userbean4=newUser();bean4.setId(1004);bean4.setName(Linda);bean4.setEmail(lin

33、da21);bean4.setGender(female);list.add(bean4);把该Servlet部署到Tomcat下，在浏览器输入接口地址HYPERLINKhttp:/localhost:8080/article/JSONDemoServlethttp:/localhost:8080/article/JSONDemoServlet，输出结果如下：id:1001,email:HYPERLINKmailto:tony%22,%22name%22:%22Tony%22,%22gender%22:%22male%22%7d,%7b%22id%22:1002,%22email%22:%22

34、jack%22,%22name%22:%22Jack%22,%22gender%22:%22male%22%7d,%7b%22id%22:1003,%22email%22:%22,%22name%22:%22Marry%22,%22gender%22:%22female%22%7d,%7b%22id%22:1004,%22email%22:%22linda21%22,%22name%22:%22Linda%22,%22gender%22:%22femaletony,name:Tony,gender:male,id:1002,email:jack,name:Jack,gender:male,id

35、:1003,email:,name:Marry,gender:female,id:1004,email:linda21,name:Linda,gender:female2、手机客户端程序准备好服务端的接口后，接下来就是准备写客户端的程序了。打开Eclipse新建一个Android项目。我们创建一个名为MainActivity的Activity类，如下图所示：因为要访问外部网络，所以要在AndroidManifest.xml文件里增加一行安全许可：这样我们的应用程序就可以访问网络了。接着修改布局文件reslayoutmain.xml，增加一个TextView对象，用来显示解析后的用户数据。HYP

36、ERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9viewplainHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9copytoclipboardHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9printHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73

37、B558E9?AndroidSDK提供了Apache的HttpClient类处理网络访问，相信很多读者朋友都在其他项目当中用到过HttpClient。我写了一个方法，获取某一网址的网页内容，代码如下：HYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9viewplainHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9copytoclipboardHYPERLINK/article/show/129;jsessioni

38、d=B5B61D9FD03EDDC65C50F7FA73B558E9printHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9?/*获取网址内容*paramurl*return*throwsException*/privateStringgetContent(Stringurl)throwsExceptionStringBuildersb=newStringBuilder();HttpClientclient=newDefaultHttpClient();HttpParamshttpParams=cli

39、ent.getParams();/设置网络超时参数HttpConnectionParams.setConnectionTimeout(httpParams,3000);HttpConnectionParams.setSoTimeout(httpParams,5000);HttpResponseresponse=client.execute(newHttpGet(url);HttpEntityentity=response.getEntity();if(entity!=null)BufferedReaderreader=newBufferedReader(newInputStreamReader

40、(entity.getContent(),UTF-8),8192);Stringline=null;while(line=reader.readLine()!=null)sb.append(line+n);reader.close();returnsb.toString();/*获取网址内容*paramurl*return*throwsException*/privateStringgetContent(Stringurl)throwsExceptionStringBuildersb=newStringBuilder();HttpClientclient=newDefaultHttpClien

41、t();HttpParamshttpParams=client.getParams();/设置网络超时参数HttpConnectionParams.setConnectionTimeout(httpParams,3000);HttpConnectionParams.setSoTimeout(httpParams,5000);HttpResponseresponse=client.execute(newHttpGet(url);HttpEntityentity=response.getEntity();if(entity!=null)BufferedReaderreader=newBuffere

42、dReader(newInputStreamReader(entity.getContent(),UTF-8),8192);Stringline=null;while(line=reader.readLine()!=null)sb.append(line+n);reader.close();returnsb.toString();修改MainActivity.java，在onCreate方法里增加解析服务端接口内容的代码，如下所示：HYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9viewplainHYP

43、ERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9copytoclipboardHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9printHYPERLINK/article/show/129;jsessionid=B5B61D9FD03EDDC65C50F7FA73B558E9?OverridepublicvoidonCreate(BundlesavedInstanceState)super.onCreate(savedInstanceState