【Java爬虫】008-网页内容解析：JSON解析

落日映苍穹つ 2023-10-05 09:23 98阅读 0赞

# 一、JSON矫正 #

## 1、概述 ##

使用网络爬虫向服务器发送请求时，服务器经常返回的数据是包含JSON的字符串，如下所示：

jQuery6({
    	"id":"07",
    	"language":"C++",
    	"edition":"second",
    	"author":"E.Balagurusamy"
    })

上述字符串虽包含JSON，但并不能直接用org.json、Gson和Fastjson等工具进行直接解析，因为其头部和尾部包含多余的字符（“jQuery6(”和“)”）。为使上述字符串能够正常解析，需要对其进行预处理（掐头去尾）操作，将其转化成标准的JSON字符串。

## 2、代码示例 ##

package com.zb.book.parse;
    
    //JSON预处理
    public class ParseJSON {
        public static void main(String[] args) {
            //JSON
            String json = "jQuery6({\n" +
                    "\t\"id\":\"07\",\n" +
                    "\t\"language\":\"C++\",\n" +
                    "\t\"edition\":\"second\",\n" +
                    "\t\"author\":\"E.Balagurusamy\"\n" +
                    "})";
            //预处理
            String attr = json.split("\\(")[1];
            System.out.println(attr.substring(0,attr.length()-1));
        }
    }

### 运行结果： ###

{
    	"id":"07",
    	"language":"C++",
    	"edition":"second",
    	"author":"E.Balagurusamy"
    }

## 3、补充 ##

与处理好的JSON字符串可以复制到JSON在线校准网站进行校准（常用）；

# 二、org.json解析JSON #

## 1、概述 ##

org.json是Java中常用的一款JSON解析工具，其常用的两个类是JSONObject和JSONArray；

## 2、Maven坐标 ##

<dependency>
        <groupId>org.json</groupId>
        <artifactId>json</artifactId>
        <version>20200518</version>
    </dependency>

## 3、JSONObject类 ##

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzI5Njg5MzQz_size_16_color_FFFFFF_t_70][]

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## 4、代码演示 ##

### 说明： ###

在解析数据时，常用getString(String key)方法获取JSON数据中key值对应的value值；

### 代码： ###

package com.zb.book.parse;
    
    import org.json.JSONObject;
    
    //JSON解析
    public class ParseJSON {
        public static void main(String[] args) {
            //JSON
            String json = "jQuery6({\n" +
                    "\t\"id\":\"07\",\n" +
                    "\t\"language\":\"C++\",\n" +
                    "\t\"edition\":\"second\",\n" +
                    "\t\"author\":\"E.Balagurusamy\"\n" +
                    "})";
            //预处理
            String attr = json.split("\\(")[1];
            attr = attr.substring(0,attr.length()-1);
            //解析
            JSONObject jsonObject = new JSONObject(attr);
            System.out.println(jsonObject.getString("id"));
            System.out.println(jsonObject.getString("language"));
            System.out.println(jsonObject.getString("edition"));
            System.out.println(jsonObject.getString("author"));
        }
    }

### 运行结果： ###

07
    C++
    second
    E.Balagurusamy

## 5、JSONArray类 ##

### 概述： ###

JSONArray类的功能是解析JSON数组，该类中包括一些实例化JSONArray对象的构造方法、获取指定JSONObject对象的方法等。

### 代码演示： ###

package com.zb.book.parse;
    
    import org.json.JSONArray;
    import org.json.JSONObject;
    
    //JSON解析
    public class ParseJSON {
        public static void main(String[] args) {
            //JSON
            String json = "jQuery6([{\n" +
                    "\t\"id\":\"07\",\n" +
                    "\t\"language\":\"C++\",\n" +
                    "\t\"edition\":\"second\",\n" +
                    "\t\"author\":\"E.Balagurusamy\"\n" +
                    "},{\n" +
                    "\t\"id\":\"08\",\n" +
                    "\t\"language\":\"C++\",\n" +
                    "\t\"edition\":\"second\",\n" +
                    "\t\"author\":\"E.Balagurusamy\"\n" +
                    "}])";
            //预处理
            String attr = json.split("\\(")[1];
            attr = attr.substring(0,attr.length()-1);
            //解析
            JSONArray jsonArray = new JSONArray(attr);
            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject jsonObject = jsonArray.getJSONObject(i);
                System.out.println(jsonObject.getString("id"));
                System.out.println(jsonObject.getString("language"));
                System.out.println(jsonObject.getString("edition"));
                System.out.println(jsonObject.getString("author"));
                System.out.println();
            }
        }
    }

### 运行结果： ###

07
    C++
    second
    E.Balagurusamy
    
    08
    C++
    second
    E.Balagurusamy

# 三、Gson解析JSON #

## 1、概述 ##

Gson是Google提供的处理JSON数据的Java类库，主要用于转换Java对象和JSON对象；

## 2、Maven坐标 ##

<dependency>
        <groupId>com.google.code.gson</groupId>
        <artifactId>gson</artifactId>
        <version>2.8.6</version>
    </dependency>

## 3、代码示例 ##

### 解析JSON对象： ###

package com.zb.book.parse.gson;
    
    import com.google.gson.Gson;
    
    //Gson解析JSON对象
    public class ParseJSONObject {
        public static void main(String[] args) {
            //实例化Gson对象
            Gson gson = new Gson();//方法一
            //Gson gson = new GsonBuilder().create();方法二
            String json = "{\n" +
                    "\t\"name\":\"Java程序设计\",\n" +
                    "\t\"page\":\"800\",\n" +
                    "\t\"money\":\"98\"\n" +
                    "}";
            //解析成Book对象
            Book book = gson.fromJson(json, Book.class);
            System.out.println(book.toString());
            //book{name='Java程序设计', page='800', money='98'}
        }
    }
    class Book {
        private String name;
        private String page;
        private String money;
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getPage() {
            return page;
        }
    
        public void setPage(String page) {
            this.page = page;
        }
    
        public String getMoney() {
            return money;
        }
    
        public void setMoney(String money) {
            this.money = money;
        }
    
        @Override
        public String toString() {
            return "book{" +
                    "name='" + name + '\'' +
                    ", page='" + page + '\'' +
                    ", money='" + money + '\'' +
                    '}';
        }
    }

### 解析JSON对象数组： ###

package com.zb.book.parse.gson;
    
    import com.google.gson.Gson;
    import com.google.gson.reflect.TypeToken;
    
    import java.lang.reflect.Type;
    import java.util.List;
    
    //Gson解析JSON对象
    public class ParseJSONObject {
        public static void main(String[] args) {
            //实例化Gson对象
            Gson gson = new Gson();//方法一
            //Gson gson = new GsonBuilder().create();方法二
            String json = "[{\n" +
                    "\t\"name\":\"Java程序设计\",\n" +
                    "\t\"page\":\"800\",\n" +
                    "\t\"money\":\"98\"\n" +
                    "},{\n" +
                    "\t\"name\":\"C语言程序设计\",\n" +
                    "\t\"page\":\"700\",\n" +
                    "\t\"money\":\"88\"\n" +
                    "}]";
            //TypeToken操作，可支持类型包括泛型
            Type listType = new TypeToken<List<Book>>() {}.getType();
            //转化成集合
            List<Book> list = gson.fromJson(json, listType);
            //循环打印
            for (Book book : list) {
                System.out.println(book.toString());
            }
            //book{name='Java程序设计', page='800', money='98'}
            //book{name='C语言程序设计', page='700', money='88'}
        }
    }
    class Book {
        private String name;
        private String page;
        private String money;
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getPage() {
            return page;
        }
    
        public void setPage(String page) {
            this.page = page;
        }
    
        public String getMoney() {
            return money;
        }
    
        public void setMoney(String money) {
            this.money = money;
        }
    
        @Override
        public String toString() {
            return "book{" +
                    "name='" + name + '\'' +
                    ", page='" + page + '\'' +
                    ", money='" + money + '\'' +
                    '}';
        }
    }

### 解析复杂嵌套式JSON数据： ###

**json示例：**

{
    	"name" : "訾博",
    	"tall" : "183CM",
    	"books" : [
    		{
    		"name":"Java程序设计",
    		"page":"800",
    		"money":"98"
    		},{
    			"name":"C语言程序设计",
    			"page":"700",
    			"money":"88"
    		}
    	]
    }

**java代码：**

package com.zb.book.parse.gson;
    
    import com.google.gson.Gson;
    
    import java.util.List;
    
    //Gson解析JSON对象
    public class ParseJSONObject {
        public static void main(String[] args) {
            //实例化Gson对象
            Gson gson = new Gson();//方法一
            //Gson gson = new GsonBuilder().create();方法二
            String json = "{\n" +
                    "\t\"name\" : \"訾博\",\n" +
                    "\t\"tall\" : \"183CM\",\n" +
                    "\t\"books\" : [\n" +
                    "\t\t{\n" +
                    "\t\t\"name\":\"Java程序设计\",\n" +
                    "\t\t\"page\":\"800\",\n" +
                    "\t\t\"money\":\"98\"\n" +
                    "\t\t},{\n" +
                    "\t\t\t\"name\":\"C语言程序设计\",\n" +
                    "\t\t\t\"page\":\"700\",\n" +
                    "\t\t\t\"money\":\"88\"\n" +
                    "\t\t}\n" +
                    "\t]\n" +
                    "}";
            //转化成集合
            People people = gson.fromJson(json, People.class);
            //打印
            System.out.println(people);
            List<Book> books = people.getBooks();
            for (Book book : books) {
                System.out.println(book);
            }
        }
    }
    class People{
        private String name;
        private String tall;
        private List<Book> books;
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getTall() {
            return tall;
        }
    
        public void setTall(String tall) {
            this.tall = tall;
        }
    
        public List<Book> getBooks() {
            return books;
        }
    
        public void setBooks(List<Book> books) {
            this.books = books;
        }
    
        @Override
        public String toString() {
            return "People{" +
                    "name='" + name + '\'' +
                    ", tall='" + tall + '\'' +
                    ", books=" + books +
                    '}';
        }
    }
    class Book {
        private String name;
        private String page;
        private String money;
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getPage() {
            return page;
        }
    
        public void setPage(String page) {
            this.page = page;
        }
    
        public String getMoney() {
            return money;
        }
    
        public void setMoney(String money) {
            this.money = money;
        }
    
        @Override
        public String toString() {
            return "book{" +
                    "name='" + name + '\'' +
                    ", page='" + page + '\'' +
                    ", money='" + money + '\'' +
                    '}';
        }
    }

**运行结果：**

People{name='訾博', tall='183CM', books=[book{name='Java程序设计', page='800', money='98'}, book{name='C语言程序设计', page='700', money='88'}]}
    book{name='Java程序设计', page='800', money='98'}
    book{name='C语言程序设计', page='700', money='88'}

# 四、Fastjson解析JSON #

## 1、概述 ##

Fastjson是阿里巴巴基于Java语言开发的高性能且功能完善的JSON操作类库；

Fastjson解析JSON的方式与Gson类似，都是讲JSON数据转化为JavaBean对象；

## 2、Maven坐标 ##

<dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.2.73</version>
    </dependency>

## 3、代码示例 ##

### 解析JSON对象： ###

package com.zb.book.parse.fastjson;
    
    import com.alibaba.fastjson.JSON;
    
    //使用fastJson解析JSON对象
    public class ParseJSONObject {
        public static void main(String[] args) {
            String json = "{\n" +
                    "\t\"name\":\"Java程序设计\",\n" +
                    "\t\"page\":\"800\",\n" +
                    "\t\"money\":\"98\"\n" +
                    "}";
            //使用fastJson解析JSON对象
            Book book = JSON.parseObject(json, Book.class);
            System.out.println(book.toString());
            //book{name='Java程序设计', page='800', money='98'}
        }
    }
    class Book {
        private String name;
        private String page;
        private String money;
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getPage() {
            return page;
        }
    
        public void setPage(String page) {
            this.page = page;
        }
    
        public String getMoney() {
            return money;
        }
    
        public void setMoney(String money) {
            this.money = money;
        }
    
        @Override
        public String toString() {
            return "book{" +
                    "name='" + name + '\'' +
                    ", page='" + page + '\'' +
                    ", money='" + money + '\'' +
                    '}';
        }
    }

### 解析JSON数组： ###

package com.zb.book.parse.fastjson;
    
    import com.alibaba.fastjson.JSON;
    
    import java.util.List;
    
    //使用fastJson解析JSON对象
    public class ParseJSONObject {
        public static void main(String[] args) {
            String json = "[\n" +
                    "\t{\n" +
                    "\t\"name\":\"Java程序设计\",\n" +
                    "\t\"page\":\"800\",\n" +
                    "\t\"money\":\"98\"\n" +
                    "\t},{\n" +
                    "\t\t\"name\":\"C语言程序设计\",\n" +
                    "\t\t\"page\":\"700\",\n" +
                    "\t\t\"money\":\"88\"\n" +
                    "\t}\n" +
                    "]";
            //使用fastJson解析JSON对象
            //方法一
            List<Book> books = JSON.parseArray(json, Book.class);
            //方法二
            //List<Book> books = JSON.parseObject(json, new TypeReference<List<Book>>() {});
            for (Book book : books) {
                System.out.println(book.toString());
            }
            //book{name='Java程序设计', page='800', money='98'}
            //book{name='C语言程序设计', page='700', money='88'}
        }
    }
    class Book {
        private String name;
        private String page;
        private String money;
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public String getPage() {
            return page;
        }
    
        public void setPage(String page) {
            this.page = page;
        }
    
        public String getMoney() {
            return money;
        }
    
        public void setMoney(String money) {
            this.money = money;
        }
    
        @Override
        public String toString() {
            return "book{" +
                    "name='" + name + '\'' +
                    ", page='" + page + '\'' +
                    ", money='" + money + '\'' +
                    '}';
        }
    }

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