pom中Jackson详细介绍

Jackson是基于Java平台的一套数据处理工具，被称为”最好的Java Json解析器”。它可以使我们高效、简便的处理json字符串。

我想回忆一下我在pom文件中的架包jackson-core是什么

然后发现就是解析处理json的东西

1、Jackson的版本以及maven依赖重点内容

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.7.4</version>
</dependency>

2、将java对象转换为json字符串

public class Goods {

    //商品id
    private BigInteger goodsId;


    private String data;

    //商品是否可用标志，true可用，false不可用
    private String status;

    //数据插入或者更新时间
    private String ctime;

    //商品版本号
    private Long version;

    public BigInteger getGoodsId() {
        return goodsId;
    }

    public void setGoodsId(BigInteger goodsId) {
        this.goodsId = goodsId;
    }

    public String getData() {
        return data;
    }

    public void setData(String data) {
        this.data = data;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public String getCtime() {
        return ctime;
    }

    public void setCtime(String ctime) {
        this.ctime = ctime;
    }

    public Long getVersion() {
        return version;
    }

    public void setVersion(Long version) {
        this.version = version;
    }
}

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

public class TestWriteJson1 {

     private ObjectMapper OBJECT_MAPPER = new ObjectMapper()
            .setSerializationInclusion(JsonInclude.Include.NON_EMPTY)  //类级别的设置，JsonInclude.Include.NON_EMPTY标识只有非NULL的值才会被纳入json string之中，其余的都将被忽略
            .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES) //禁止使用出现未知属性之时，抛出异常

.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
            .setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);//转化后的json的key命名格式

    @Test
    public void writeJson() throws JsonProcessingException {

        Goods goods = new Goods();
        goods.setGoodsId("1234");
        goods.setData("data");
        goods.setCtime("2017-02-24");

        String jsonStr = OBJECT_MAPPER.writeValueAsString(goods);

        System.out.println("JSON:" + jsonStr);
    }
}

3、String对象转为json格式

public class TestWriteJson2 {

     private ObjectMapper OBJECT_MAPPER = new ObjectMapper()
            .setSerializationInclusion(JsonInclude.Include.NON_EMPTY)//类级别的设置，JsonInclude.Include.NON_EMPTY标识只有非NULL的值才会被纳入json string之中，其余的都将被忽略
            .disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)//禁止使用出现未知属性之时，抛出异常

.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS)
            .setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);//转化后的json的key命名格式

    @Test
    public void writeJson() throws JsonProcessingException {

        //1、str对象的属性具有很强的统一性，属性固定
        String str = "";

        Goods goods = null;
        try {
            goods = new ObjectMapper().readValue(str, new TypeReference<Goods>() {
            });
        } catch (IOException e) {

        }

        if(goods != null){
            //取出相应属性
        }


        //2、str对象的属性没有很强的统一性，有可能属性缺失
        String str = "";
        // Jackson提供一个树节点被称为"JsonNode",ObjectMapper提供方法来读json作为树的JsonNode根节点
        JsonNode jsonNode = objectMapper.readTree(valueParser);
        List<JsonNode> dataList = jsonNode.findValues("data");
        if(dataList != null && dataList.size() > 0){
            //取出相应属性

            // 得到所有node节点的子节点名称
            Iterator<String> fieldNames = dataList.fieldNames();  
            while (fieldNames.hasNext()) { 
                String fieldName = fieldNames.next();  
                System.out.print(fieldName+" ");  
            }


            //得到某个属性值
            JsonNode goodId = dataList.get("goodId"); 

        }               
    }
}