jackson是一个用Java编写的，用来处理JSON格式数据的类库，它速度非常快，目前来看使用很广泛，逐渐替代了Gson和json-lib。
这是大神解析效率的测试数据的网站http://wangym.iteye.com/blog/738933
20141127152011390.png
最终结果是Jackson > Gson > Json-lib。这也就是为什么要掌握jackson解析的意义了
下面是我练习写的一个demo,其实使用起来和Gson比较类似****
首先建一个单例的类提供ObjectMapper对象,后面很多操作会用到这个对象
import org.codehaus.jackson.map.ObjectMapper;
/** * 只用创建一次ObjectMapper对象就可以了 */
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;
}
}
然后创建ProductBean对象
这是我解析用的json字符串
{"productProperty":[{"v":"红色","k":"颜色","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 + '}';
}
}
//商品属性
public class ProductPropertyBean {
/** * id : 1 * k : 颜色 * v : 红色
*/
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比较类似
传递对应的json字符串,和bean对象的字节码就可以了,
如果是数组就传对应的List的字节码
mMapper.readValue(jsonString, ProductBean.class);
想把bean对象转换成json字符串
同样的如果是List直接传递List对象就可以了
mMapper.writeValueAsString(objectBean);
一般也就这两种用法
还有节点解析要用到JsonNode这个对象,类似map根据key获取对应的value值然后asInt()等对应的数据类型就可以了,如果获取的是对象或数组,那只能先tostring()获取对象的json字符串才能接着解析,也就是要一层一层的解析
(注意:对象或数组用asText()获取的字符串为空,所以必须用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();
//创建ProductBean对象
ProductBean productBean = createObject();
//将对象解析成json字符串
String objectJson = toJson(productBean);
// String json = toJson2(productBean);
mObjectTvTojson.setText("toJson==="+objectJson);
//将数组转化成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);
//将json字符串解析为bean
ProductBean bean = toObjectBean(objectJson);
mTvToObject.setText("toObjectBean==="+bean.toString());
//将json字符串解析为List
ArrayList<ProductBean> list = toArrayBean(arrayJson);
mTvToList.setText("toArrayBean==="+list.toString());
//jackson节点解析
jsonNode(objectJson);
}
public void jsonNode(String objectJson) {
//{"productProperty":[{"v":"红色","k":"颜色","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();
//如果要转化成对象的话还得用 ObjectMapper的readValue(), productProperty如果用JsonNode的asText()获取的是空
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(){
//创建ProductBean对象
ProductPropertyBean color = new ProductPropertyBean(1,"颜色","红色");
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 {
//将对象解析成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 {
//将对象解析成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;
}
}
练习demo的下载https://github.com/starrysky0/jacksondemo
初次尝试写这些东西,主要是总结一下自己的学习情况,如果有什么错误或不足,真诚的希望大神们能指出来
