jackson 读文件生成object 写object到json文件_jackson writeobject-优快云博客

本文展示了如何使用Jackson库在Java中将对象转换为JSON文件，以及从JSON文件反序列化回对象。示例中，创建了一个`AccountBean`对象并将其属性设置，然后使用`ObjectMapper`和`JsonGenerator`将其写入JSON文件。同时，还演示了从JSON文件读取`AccountBean`对象的方法。

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<span style="font-size:24px;">package jiba.jacks;

import java.io.File;
import java.io.IOException;

import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.fasterxml.jackson.core.JsonEncoding;
import com.fasterxml.jackson.core.JsonFactory;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JacksonTest {
	private JsonGenerator jsonGenerator = null;
    private ObjectMapper objectMapper = null;
    private AccountBean bean = null;
    File fl = new File("F:\\javadata\\think-in-java\\src\\user.json");
    JsonFactory factory = new JsonFactory();
    @Before
    public void init() throws IOException {
        bean = new AccountBean();
        bean.setAddress("china-Guangzhou");
        bean.setEmail("hoojo_@126.com");
        bean.setId(1);
        bean.setName("hoojo");
        
        objectMapper = new ObjectMapper();
        factory.setCodec(objectMapper);
        jsonGenerator = factory.createGenerator(fl, JsonEncoding.UTF8);
    }
    @Test
    public void writeEntityJSON() throws Exception{
    	jsonGenerator.useDefaultPrettyPrinter();
    	jsonGenerator.writeObject(bean);
    	/*jsonGenerator.useDefaultPrettyPrinter();
    	jsonGenerator.writeStartObject();//开始写入json格式的字符串此语句相当于："{"  
    
  jsonGenerator.writeFieldName("name");//相当于key为"name"  
  jsonGenerator.writeString("Nacey");//相当于value为"Nacey"  
  jsonGenerator.writeStringField("sex", "male"); //方法同上//"sex":"male"  
    
  jsonGenerator.writeArrayFieldStart("Address"); //创建一个数组类似：Address:[  
  jsonGenerator.writeString("tel");  
  jsonGenerator.writeString("1555122120");  
  jsonGenerator.writeEndArray();  
    
  jsonGenerator.writeEndObject();//结束json对象  
  jsonGenerator.close(); */ 
    	AccountBean be = objectMapper.readValue(fl, AccountBean.class);  	
    	System.out.println(be.getAddress());
    }
    
    @After
    public void destory() {
        try {
            if (jsonGenerator != null) {
                jsonGenerator.flush();
            }
            objectMapper = null;
            bean = null;
            System.gc();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}
</span>