jackson是一個用Java編寫的，用來處理JSON格式數(shù)據(jù)的類庫，它速度非常快，目前來看使用很廣泛，逐漸替代了Gson和json-lib。
這是大神解析效率的測試數(shù)據(jù)的網(wǎng)站http://wangym.iteye.com/blog/738933

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最終結(jié)果是Jackson > Gson > Json-lib。這也就是為什么要掌握jackson解析的意義了
下面是我練習(xí)寫的一個demo,其實使用起來和Gson比較類似****
首先建一個單例的類提供ObjectMapper對象,后面很多操作會用到這個對象

import org.codehaus.jackson.map.ObjectMapper;
/** * 只用創(chuàng)建一次ObjectMapper對象就可以了 */
public class JacksonMapper {  
  private static ObjectMapper mapper ; 
   public static ObjectMapper getMapper(){
        if(mapper==null){
            synchronized (JacksonMapper.class){
                if(mapper == null){
                    mapper = new ObjectMapper(); 
               }
            }
        }
        return mapper; 
   }
}

然后創(chuàng)建ProductBean對象
這是我解析用的json字符串

{"productProperty":[{"v":"紅色","k":"顏色","id":1},{"v":"L","k":"尺寸","id":2}],"name":"毛衣","price":130.0,"id":1}

 import java.util.List;
public class ProductBean {
    public int id;    public String name;
    public float price;
    public List<ProductPropertyBean> productProperty;
    public ProductBean() {    }
    public ProductBean(int id, String name, float price, List<ProductPropertyBean> productProperty) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.productProperty = productProperty;
    }
    @Override
    public String toString() {
        return "ProductBean{" +
                "id=" + id +              
                ", name='" + name + '\'' +
                ", price=" + price +
                ", productProperty=" + productProperty +                '}';
    }
}

//商品屬性
public class ProductPropertyBean {
    /**     * id : 1     * k : 顏色     * v : 紅色
     */
    public int id;
    public String k;
    public String v;
    public ProductPropertyBean() {    } 
   public ProductPropertyBean(int id, String k, String v) {
        this.id = id;
        this.k = k;
        this.v = v;
    }   
 @Override
    public String toString() {
        return "ProductPropertyBean{" + 
               "id=" + id +
                ", k='" + k + '\'' +
                ", v='" + v + '\'' +                '}';
    }
}

jackson使用和Gson比較類似
傳遞對應(yīng)的json字符串,和bean對象的字節(jié)碼就可以了,
如果是數(shù)組就傳對應(yīng)的List的字節(jié)碼

mMapper.readValue(jsonString, ProductBean.class);

想把bean對象轉(zhuǎn)換成json字符串
同樣的如果是List直接傳遞List對象就可以了

mMapper.writeValueAsString(objectBean);

一般也就這兩種用法
還有節(jié)點解析要用到JsonNode這個對象,類似map根據(jù)key獲取對應(yīng)的value值然后asInt()等對應(yīng)的數(shù)據(jù)類型就可以了,如果獲取的是對象或數(shù)組,那只能先tostring()獲取對象的json字符串才能接著解析,也就是要一層一層的解析
(注意:對象或數(shù)組用asText()獲取的字符串為空,所以必須用tostring())

 JsonNode jsonNode = mMapper.readTree(objectJson); 
 JsonNode name = jsonNode.get("name"); 
 JsonNode price = jsonNode.get("price"); 
 JsonNode id = jsonNode.get("id");
name.asText();

public class MainActivity extends AppCompatActivity {
    private static final String TAG ="MainActivity" ;
    @Bind(R.id.tv_object_tojson) 
   TextView mObjectTvTojson; 
   @Bind(R.id.tv_array_tojson)
    TextView mArrayTvTojson;
    @Bind(R.id.tv_toObject)
    TextView mTvToObject;
    @Bind(R.id.tv_toList) 
   TextView mTvToList;
    @Bind(R.id.activity_main)
    LinearLayout mActivityMain;
    private ObjectMapper mMapper;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);
        mMapper = JacksonMapper.getMapper();
        //創(chuàng)建ProductBean對象
        ProductBean productBean = createObject();
        //將對象解析成json字符串
        String objectJson = toJson(productBean);
       // String json = toJson2(productBean);
        mObjectTvTojson.setText("toJson==="+objectJson);
        //將數(shù)組轉(zhuǎn)化成json字符串
        ArrayList<ProductBean> beanArrayList = new ArrayList<>(); 
       beanArrayList.add(productBean);
        beanArrayList.add(productBean);
        beanArrayList.add(productBean);
        String arrayJson =toJson(beanArrayList);
        mArrayTvTojson.setText("toJson==="+arrayJson);
        //將json字符串解析為bean
        ProductBean bean = toObjectBean(objectJson);
        mTvToObject.setText("toObjectBean==="+bean.toString()); 
       //將json字符串解析為List 
       ArrayList<ProductBean> list = toArrayBean(arrayJson);
        mTvToList.setText("toArrayBean==="+list.toString());
        //jackson節(jié)點解析 
       jsonNode(objectJson);
    }
    public void jsonNode(String objectJson) { 
       //{"productProperty":[{"v":"紅色","k":"顏色","id":1},{"v":"L","k":"尺寸","id":2}],"name":"毛衣","price":130.0,"id":1}
        try { 
           JsonNode jsonNode = mMapper.readTree(objectJson); 
           JsonNode productProperty = jsonNode.get("productProperty");
            JsonNode name = jsonNode.get("name");
            JsonNode price = jsonNode.get("price");
            JsonNode id = jsonNode.get("id");
            String propertyString = productProperty.toString(); 
           //如果要轉(zhuǎn)化成對象的話還得用 ObjectMapper的readValue(), productProperty如果用JsonNode的asText()獲取的是空 
           ArrayList productPropertyBeans = mMapper.readValue(propertyString, new ArrayList<ProductPropertyBean>().getClass());
            Log.d(TAG, "jsonNode:name: "+name.asText()); 
           Log.d(TAG, "jsonNode:id: "+id.asInt());
            Log.d(TAG, "jsonNode: price:"+price.asDouble());
            Log.d(TAG, "jsonNode:
 productPropertyBeans"+productPropertyBeans.toString());
        } catch (IOException e) { 
           e.printStackTrace();
            Log.d(TAG, "jsonNode: "+e.toString());
        } 
   }
    public ProductBean createObject(){ 
       //創(chuàng)建ProductBean對象
        ProductPropertyBean color = new ProductPropertyBean(1,"顏色","紅色"); 
       ProductPropertyBean size = new ProductPropertyBean(2,"尺寸","L"); 
       ArrayList<ProductPropertyBean> productPropertyBeen = new ArrayList<>();  
      productPropertyBeen.add(color);        productPropertyBeen.add(size);
        ProductBean productBean = new ProductBean(1,"毛衣",130,productPropertyBeen);
        return productBean;
    }
    public String toJson(Object o){
        String s;
        try { 
           //將對象解析成json字符串
          s = mMapper.writeValueAsString(o);
        } catch (IOException e) {
            e.printStackTrace();
            s = e.toString(); 
       } 
       Log.i(TAG, "getJson: "+s); 
       return s;
    }
    public String toJson2(Object o){ 
       String s;
        try {
            //將對象解析成json字符串 
           StringWriter stringWriter = new StringWriter();
            JsonFactory jsonFactory = mMapper.getJsonFactory(); 
           JsonGenerator jgen = jsonFactory.createJsonGenerator(stringWriter); 
           mMapper.writeValue(jgen,o);
            jgen.flush();
            jgen.close();
            s = stringWriter.toString();
            stringWriter.close();
        } catch (IOException e) { 
           e.printStackTrace();
            s = e.toString();
        }
        Log.i(TAG, "getJson: "+s);
        return s; 
   }
    public ProductBean toObjectBean(String json){
        ProductBean productBean = null;
        try {
          productBean = mMapper.readValue(json, ProductBean.class); 
       } catch (IOException e) { 
           e.printStackTrace(); 
       } 
       return productBean;
    }
    public ArrayList<ProductBean> toArrayBean(String json){
       ArrayList list = null; 
       try {
            list = mMapper.readValue(json, new ArrayList<ProductBean>().getClass());
        } catch (IOException e) { 
           e.printStackTrace();
        } 
       return list;
    }
}

練習(xí)demo的下載https://github.com/starrysky0/jacksondemo
初次嘗試寫這些東西,主要是總結(jié)一下自己的學(xué)習(xí)情況,如果有什么錯誤或不足,真誠的希望大神們能指出來