Java基础-处理json字符串解析案例

　　　　　　　　　　　　　　　　Java基础-处理json字符串解析案例

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　作者：尹正杰

版权声明：原创作品，谢绝转载！否则将追究法律责任。

　　作为一名开发人员，想必大家或多或少都有接触到XML文件，XML全称为“extensible markup language”，即可扩展性标记语言。它由于可读性很好，但是在网络传输上，这种数据格式往往很占用带宽等诸多缺点，因此就诞生了Json，它比XML数据更小、更快、更容易解析。数据由名称-值 对表示，由逗号分隔开，花括号保存对象，方括号保存数组。Json值可以是：数字/字符串/逻辑值/数组/对象/null。

　　接下来我们就一起看看如何创建一个json文件以及如何解析json文件。

一.java自定义对象对象和json字符串的互转

1>.添加Maven依赖（添加最后一个依赖json即可）

 <?xml version="1.0" encoding="UTF-8"?>
 <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/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>

     <groupId>groupId</groupId>
     <artifactId>MyHadoop</artifactId>
     <version>1.0-SNAPSHOT</version>

     <dependencies>
         <dependency>
             <groupId>org.apache.hadoop</groupId>
             <artifactId>hadoop-client</artifactId>
             <version>2.7.3</version>
         </dependency>

         <!-- https://mvnrepository.com/artifact/junit/junit -->
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
             <version>4.12</version>
             <scope>test</scope>
         </dependency>

         <dependency>
             <groupId>mysql</groupId>
             <artifactId>mysql-connector-java</artifactId>
             <version>5.1.17</version>
         </dependency>
         <dependency>
             <groupId>com.alibaba</groupId>
             <artifactId>fastjson</artifactId>
             <version>1.2.47</version>
         </dependency>

     </dependencies>

 </project>

2>.具体实现代码如下：

 /*
 @author :yinzhengjie
 Blog:http://www.cnblogs.com/yinzhengjie/tag/Java%E5%9F%BA%E7%A1%80/
 EMAIL:y1053419035@qq.com
 */
 package cn.org.yinzhengjie.json;

 public class Teacher {
     private String name;
     private int age;

     public Teacher(String name, int age) {
         this.name = name;
         this.age = age;
     }

     public Teacher() {
     }

     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;
     }

     public String toString() {
         return "Teacher{" + "name='" + name  + ", age=" + age + '}';
     }
 }

Teacher.java 文件内容

 /*
 @author :yinzhengjie
 Blog:http://www.cnblogs.com/yinzhengjie/tag/Java%E5%9F%BA%E7%A1%80/
 EMAIL:y1053419035@qq.com
 */
 package cn.org.yinzhengjie.json;

 import com.alibaba.fastjson.JSONObject;

 import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;

 public class JsonOperation {
     public static final String filePath =  "D:\\10.Java\\IDE\\yhinzhengjieData\\MyHadoop\\JSON\\teacher.txt";

     public static void main(String[] args) throws Exception {
         generatingJSON();
         System.out.println("=============我是分割线=============");
         parsingJSON();
     }
     //生成json文本
     private static void generatingJSON() throws IOException {
         Teacher yzj = new Teacher("尹正杰", 18);
         String json = JSONObject.toJSONString(yzj);
         System.out.println(json);
         FileOutputStream fos = new FileOutputStream(filePath);
         byte[] buf = new byte[1024];
         fos.write(json.getBytes());
         fos.close();
     }

     //解析json文本
     private static void parsingJSON() throws IOException {
         byte[] buf = new byte[1024];
         FileInputStream fis = new FileInputStream(filePath);
         //由于我的文件较小，为了实验方便我就一次性读取出来了
         JSONObject json = JSONObject.parseObject( new String(buf,0,fis.read(buf)));
         System.out.println(json);
     }
 }

 /*
 以上代码执行结果如下:
 {"age":18,"name":"尹正杰"}
 =============我是分割线=============
 {"name":"尹正杰","age":18}
  */

二.Java数据类型和Json互相转换案例

以下是list和json字符串的互转，当然，map的转换json和其方法类似，我这里就不多举例了：

 /*
 @author :yinzhengjie
 Blog:http://www.cnblogs.com/yinzhengjie/tag/Java%E5%9F%BA%E7%A1%80/
 EMAIL:y1053419035@qq.com
 */
 package cn.org.yinzhengjie.json;

 public class Teacher {
     private String name;
     private int age;

     public Teacher(String name, int age) {
         this.name = name;
         this.age = age;
     }

     public Teacher() {
     }

     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;
     }

     public String toString() {
         return "Teacher{" + "name='" + name  + ", age=" + age + '}';
     }
 }

Teacher.java 文件内容

 /*
 @author :yinzhengjie
 Blog:http://www.cnblogs.com/yinzhengjie/tag/Java%E5%9F%BA%E7%A1%80/
 EMAIL:y1053419035@qq.com
 */
 package cn.org.yinzhengjie.json;

 import com.alibaba.fastjson.JSON;
 import com.alibaba.fastjson.JSONArray;
 import com.alibaba.fastjson.JSONObject;

 import java.util.ArrayList;
 import java.util.List;

 public class JsonOperation {

     public static void main(String[] args) throws Exception {
         listToJSON();
         System.out.println("=============我是分割线=============");
         jsonToList();
     }
     public static void listToJSON(){
         Teacher yzj = new Teacher("尹正杰",18);
         Teacher yzj1 = new Teacher("yinzhengjie",19);
         Teacher yzj2 = new Teacher("YINZHENGJIE",20);
         List<Teacher> lists=new ArrayList<Teacher>();
         lists.add(yzj);
         lists.add(yzj1);
         lists.add(yzj2);
         String listArray=JSONArray.toJSONString(lists);
         System.out.println("arrayList:"+listArray);
     }

     public static void jsonToList(){
         String str ="{\"names\":[\"尹正杰\",\"yinzhengjie\"]}";
         JSONObject jo = JSON.parseObject(str);
         JSONArray jsonArray = jo.getJSONArray("names");
         for (Object o : jsonArray) {
             System.out.println(o.toString());
         }
     }
 }

 /*
 以上代码执行结果如下:
 arrayList:[{"age":18,"name":"尹正杰"},{"age":19,"name":"yinzhengjie"},{"age":20,"name":"YINZHENGJIE"}]
 =============我是分割线=============
 尹正杰
 yinzhengjie
  */

三.小试牛刀

　　是不是觉得json处理其实蛮简单的，不是吗？接下来我们来练习以下，解析以下的字符串：需要解析商家评论数据：

{"reviewPics":null,"extInfoList":[{"title":"contentTags","values":["环境优雅","性价比高","干净卫生","停车方便","音响效果好"],"desc":"","defineType":0},{"title":"tagIds","values":["24","300","852","506","173"],"desc":"","defineType":0}],"expenseList":null,"reviewIndexes":[2],"scoreList":null}

 /*
 @author :yinzhengjie
 Blog:http://www.cnblogs.com/yinzhengjie/tag/Java%E5%9F%BA%E7%A1%80/
 EMAIL:y1053419035@qq.com
 */
 package cn.org.yinzhengjie.json;

 import com.alibaba.fastjson.JSON;
 import com.alibaba.fastjson.JSONArray;
 import com.alibaba.fastjson.JSONObject;

 import java.util.ArrayList;
 import java.util.List;

 public class JsonOperation {

     public static void main(String[] args) throws Exception {
         String comment = "{\"reviewPics\":null,\"extInfoList\":[{\"title\":\"contentTags\",\"values\":[\"环境优雅\",\"性价比高\",\"干净卫生\",\"停车方便\",\"音响效果好\"],\"desc\":\"\",\"defineType\":0},{\"title\":\"tagIds\",\"values\":[\"24\",\"300\",\"852\",\"506\",\"173\"],\"desc\":\"\",\"defineType\":0}],\"expenseList\":null,\"reviewIndexes\":[2],\"scoreList\":null}";
         List<String> taggen = taggen(comment);
         for (String s : taggen) {
             System.out.println(s);
         }

     }
     /**
      * 解析商家评论数据
      */
     public static List<String> taggen(String comment){
         JSONObject jo = JSON.parseObject(comment);
         JSONArray jArray = jo.getJSONArray("extInfoList");
         if(jArray != null && jArray.size() != 0){
             List<String> list = new ArrayList<String>();
             //通过jArray得到第一个json串，作为json对象
             JSONObject jo2 = jArray.getJSONObject(0);
             JSONArray jArray2 = jo2.getJSONArray("values");
             if(jArray2 != null && jArray2.size() != 0){
                 for (Object o : jArray2) {
                     //System.out.println(o.toString());
                     list.add(o.toString());
                 }
                 return list;
             }
         }
         return null;
     }
 }

 /*
 以上代码执行结果如下:
 环境优雅
 性价比高
 干净卫生
 停车方便
 音响效果好
  */

”