服務器端生成JSON數據

JSON的全稱是：JavaScript Object Notation，是一種輕量級的數據交換格式。它構建於兩種結構：

1、"名稱/值" 對的集合(a collection of name / value pairs)。

不同的語言中，它被理解爲對象(Object)，記錄(Record)，結構(struct)，字典(Dictionary)，哈希表(HashTable)，有鍵列表(Keyed list)，或者關聯數組(Associative array)。

2、值的有序列表(An ordered list of values)。在大部分語言中，它被理解爲數組(array)。

JSON數據格式的特點：

JSON對象是一個無序的" '名稱/值' 對"的集合，一個對象以“{”(左括號)開始， 以"}"(右括號)結束，每個"名稱"後跟一個"："(冒號)，名稱/值 對之間使用"，"(逗號)分隔。

如：

{

"name":"jackson",

"age":100

}

稍微複雜一點的情況，數組是值的有序集合，一個數組以“[”(左中括號)開始，以"]"(右中括號)結束。值之間使用","(逗號)分隔。

如：

{

"studengs":

[

{"name": "jackson", "age": 100},

{"name": "michael", "age": 51},

]

}

源代碼：

Person.java

<span style="font-size:14px;">package com.json.domain; 
 
public class Person { 
    private int id; 
    private String name; 
    private String address; 
     
    public Person() { 
        super(); 
    } 
    public Person(int id, String name, String addrss) { 
        super(); 
        this.id = id; 
        this.name = name; 
        this.address = addrss; 
    } 
    public int getId() { 
        return id; 
    } 
    public void setId(int id) { 
        this.id = id; 
    } 
    public String getName() { 
        return name; 
    } 
    public void setName(String name) { 
        this.name = name; 
    } 
    public String getAddress() { 
        return address; 
    } 
    public void setAddress(String address) { 
        this.address = address; 
    } 
    @Override 
    public String toString() { 
        return "Person [addrss=" + address + ", id=" + id + ", name=" + name 
                + "]"; 
    } 
     
} 
</span>

JsonService.java

package com.json.service; 
import java.util.ArrayList; 
import java.util.HashMap; 
import java.util.List; 
import java.util.Map; 
import com.json.domain.Person; 
public class JsonService { 
    public JsonService() { 
    } 
    public Person getPerson(){ 
        Person person = new Person(1001,"jack","上海黃浦區"); 
        return person; 
    } 
    public List<Person> getListPerson(){ 
        List<Person> list = new ArrayList<Person>(); 
        Person person1 = new Person(1001,"jack","上海黃浦區"); 
        Person person2 = new Person(1002,"rose","上海閔行區"); 
        Person person3 = new Person(1003,"mick","上海黃浦區"); 
        list.add(person1); 
        list.add(person2); 
        list.add(person3); 
        return list; 
    } 
    public List<String> getListString(){ 
        List<String> list = new ArrayList<String>(); 
        list.add("北京"); 
        list.add("上海"); 
        list.add("湖南"); 
        return list; 
    } 
    public List<Map<String,Object>> getListMaps(){ 
        List<Map<String,Object>> list = new ArrayList<Map<String,Object>>(); 
        Map<String,Object> map1 = new HashMap<String, Object>(); 
        Map<String,Object> map2 = new HashMap<String, Object>(); 
        map1.put("id", 1001); 
        map1.put("name", "jack"); 
        map1.put("address", "北京"); 
        map2.put("id", 1001); 
        map2.put("name", "rose"); 
        map2.put("address", "上海"); 
        list.add(map1); 
        list.add(map2); 
        return list; 
    } 
} 

JsonServlet.java

package com.json.servlet; 
import java.io.IOException; 
import java.io.PrintWriter; 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import com.json.service.JsonService; 
import com.json.tools.JsonTools; 
public class JsonServlet extends HttpServlet { 
    private JsonService service; 
    /** 
     * Constructor of the object. 
     */ 
    public JsonServlet() { 
        super(); 
    } 
    /** 
     * Destruction of the servlet. <br> 
     */ 
    public void destroy() { 
        super.destroy(); // Just puts "destroy" string in log 
        // Put your code here 
    } 
 
    /** 
     * The doGet method of the servlet. <br> 
     * 
     * This method is called when a form has its tag value method equals to get. 
     *   
     * @param request the request send by the client to the server 
     * @param response the response send by the server to the client 
     * @throws ServletException if an error occurred 
     * @throws IOException if an error occurred 
     */ 
    public void doGet(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException { 
        this.doPost(request, response); 
    } 
 
    /** 
     * The doPost method of the servlet. <br> 
     * 
     * This method is called when a form has its tag value method equals to post. 
     *   
     * @param request the request send by the client to the server 
     * @param response the response send by the server to the client 
     * @throws ServletException if an error occurred 
     * @throws IOException if an error occurred 
     */ 
    public void doPost(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException { 
        response.setContentType("text/html;charset=utf-8"); 
        request.setCharacterEncoding("utf-8"); 
        response.setCharacterEncoding("utf-8"); 
        PrintWriter out = response.getWriter(); 
         
        String jsonString = ""; 
        String action_flag = request.getParameter("action_flag"); 
        if(action_flag.equals("person")){ 
            jsonString = JsonTools.createJsonString("person", service.getPerson()); 
        }else if(action_flag.equals("persons")){ 
            jsonString = JsonTools.createJsonString("persons", service.getListPerson()); 
        }else if(action_flag.equals("listString")){ 
            jsonString = JsonTools.createJsonString("listString", service.getListString()); 
        }else if(action_flag.equals("listMap")){ 
            jsonString = JsonTools.createJsonString("listMap", service.getListMaps()); 
        } 
        out.println(jsonString); 
        out.flush(); 
        out.close(); 
    } 
    /** 
     * Initialization of the servlet. <br> 
     * 
     * @throws ServletException if an error occurs 
     */ 
    public void init() throws ServletException { 
        service = new JsonService(); 
    } 
} 

web.xml中servlet映射

<span style="font-size:14px;"><servlet> 
    <description>This is the description of my J2EE component</description> 
    <display-name>This is the display name of my J2EE component</display-name> 
    <servlet-name>JsonServlet</servlet-name> 
    <servlet-class>com.json.servlet.JsonServlet</servlet-class> 
  </servlet> 
 
  <servlet-mapping> 
    <servlet-name>JsonServlet</servlet-name> 
    <url-pattern>/servlet/JsonServlet</url-pattern> 
  </servlet-mapping> </span>

<span style="font-size:14px;">
</span>

訪問地址一：http://wulianghuan-pc:8080/JsonProject/servlet/JsonServlet?action_flag=person

輸出以下結果：

{"persons":{"address":"上海黃浦區","id":1001,"name":"jack"}}

訪問地址二：http://wulianghuan-pc:8080/JsonProject/servlet/JsonServlet?action_flag=persons

輸出以下結果：

{"persons":[{"address":"上海黃浦區","id":1001,"name":"jack"},{"addrss":"上海閔行區","id":1002,"name":"rose"},{"address":"上海黃浦區","id":1003,"name":"mick"}]}

訪問地址三：http://wulianghuan-pc:8080/JsonProject/servlet/JsonServlet?action_flag=listString

輸出以下結果：

{"persons":["北京","上海","湖南"]}

訪問地址四：http://wulianghuan-pc:8080/JsonProject/servlet/JsonServlet?action_flag=listMap

輸出以下結果：

{"persons":[{"id":1001,"address":"北京","name":"jack"},{"id":1001,"address":"上海","name":"rose"}]}