java读取json文件（Gson）

叁歲伎倆 2021-12-18 06:49 695阅读 0赞

**一、Gson的基本用法**

Gson提供了fromJson() 和toJson() 两个直接用于解析和生成的方法，前者实现反序列化，后者实现了序列化；同时每个方法都提供了重载方法;Gson提供了良好的容错率，即使你的json文件没有写对，例如少写引号或者多写引号，都可以解析出来。  
二、举例  
读取下列文件中的内容  
![在这里插入图片描述][20190702204625240.png]

package com.fjh.json;
    
    public class Person { 
    	private int id;
    	private String name;
    	private int age;
    	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 int getAge() { 
    		return age;
    	}
    	public void setAge(int age) { 
    		this.age = age;
    	}
    	@Override
    	public String toString() { 
    		return "Person [id=" + id + ", name=" + name + ", age=" + age + "]";
    	}
    }

package com.fjh.json;
    
    import java.io.BufferedReader;
    import java.io.File;
    import java.io.FileReader;
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.List;
    
    public class Data { 
    
    	private int rows;
    	private List<Person> datas = new ArrayList<Person>();
    	String time;
    
    	public String getTime() { 
    		return time;
    	}
    
    	public void setTime(String time) { 
    		this.time = time;
    	}
    
    	public int getRows() { 
    		return rows;
    	}
    
    	public void setRows(int rows) { 
    		this.rows = rows;
    	}
    
    	public List<Person> getDatas() { 
    		return datas;
    	}
    
    	public void setDatas(List<Person> datas) { 
    		this.datas = datas;
    	}
    
    	public String getFileContent(String fileName) { 
    		String userPath = System.getProperty("user.dir");
    		StringBuffer content = new StringBuffer();
    		BufferedReader reader = null;
    		try { 
    			reader = new BufferedReader(new FileReader(new File(userPath + "/" + fileName)));
    			String line = null;
    			while ((line = reader.readLine()) != null) { 
    				content.append(line);
    			}
    		} catch (Exception e) { 
    			e.printStackTrace();
    		} finally { 
    			try { 
    				if (reader != null)
    					reader.close();
    			} catch (IOException e) { 
    				e.printStackTrace();
    			}
    		}
    
    		return content.toString();
    	}
    
    	@Override
    	public String toString() { 
    		return "Data [rows=" + rows + ", datas=" + datas + ", time=" + time + "]";
    	}
    	
    	
    }

package com.fjh.json;
    
    import com.google.gson.Gson;
    
    public class GsonTest { 
    
    	public static void main(String[] args) { 
    		Data data = new Data();
    		
    		String content = data.getFileContent("Persons.json");
    		Gson gson = new Gson();
    		Data fromJson = gson.fromJson(content, Data.class);
    		System.out.println(fromJson);
    	}
    
    }

**读取结果**  
Data \[rows=3, datas=\[Person \[id=1, name=张三, age=20\], Person \[id=2, name=zz, age=21\], Person \[id=3, name=lw, age=22\]\], time=2019-07-01\]

[20190702204625240.png]: /images/20211218/b0281cfd11c74824a1490115377a4d66.png