调用第三方接口时，需要将javabean转换成map，这是为啥
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因为现在的接口一般都是用json字符串传输。javaBean转成map之后，再转成json字符串传过去，第三方接口就能直接转换成json格式获取对应的信息 参考技术A 方便转换成XML或 JSON等格式~~~~~~~~~~~
gson和fastjson将json对象转换成javaBean 简单对照
同事离职，项目后端部分的迭代和重构后面由我接手.
今天看项目代码时，发现项目使用了Gson，用于将json字符串转换成javaBean.
以前没使用过Gson，随即，简单入了个们，
想起fastjson也有将json字符串转换成javaBean的API，随即简单比较了下源码.
fastjson中的API如下：
/**
* @since 1.2.9
*/
public <T> T toJavaObject(Class<T> clazz) {
return TypeUtils.cast(this, clazz, ParserConfig.getGlobalInstance());
}
@SuppressWarnings({ "unchecked", "rawtypes" })
public static <T> T cast(Object obj, Class<T> clazz, ParserConfig config) {
if (obj == null) {
return null;
}
if (clazz == null) {
throw new IllegalArgumentException("clazz is null");
}
if (clazz == obj.getClass()) {
return (T) obj;
}
if (obj instanceof Map) {
if (clazz == Map.class) {
return (T) obj;
}
Map map = (Map) obj;
if (clazz == Object.class && !map.containsKey(JSON.DEFAULT_TYPE_KEY)) {
return (T) obj;
}
return castToJavaBean((Map<String, Object>) obj, clazz, config);
}
if (clazz.isArray()) {
if (obj instanceof Collection) {
Collection collection = (Collection) obj;
int index = 0;
Object array = Array.newInstance(clazz.getComponentType(), collection.size());
for (Object item : collection) {
Object value = cast(item, clazz.getComponentType(), config);
Array.set(array, index, value);
index++;
}
return (T) array;
}
if (clazz == byte[].class) {
return (T) castToBytes(obj);
}
}
if (clazz.isAssignableFrom(obj.getClass())) {
return (T) obj;
}
if (clazz == boolean.class || clazz == Boolean.class) {
return (T) castToBoolean(obj);
}
if (clazz == byte.class || clazz == Byte.class) {
return (T) castToByte(obj);
}
// if (clazz == char.class || clazz == Character.class) {
// return (T) castToCharacter(obj);
// }
if (clazz == short.class || clazz == Short.class) {
return (T) castToShort(obj);
}
if (clazz == int.class || clazz == Integer.class) {
return (T) castToInt(obj);
}
if (clazz == long.class || clazz == Long.class) {
return (T) castToLong(obj);
}
if (clazz == float.class || clazz == Float.class) {
return (T) castToFloat(obj);
}
if (clazz == double.class || clazz == Double.class) {
return (T) castToDouble(obj);
}
if (clazz == String.class) {
return (T) castToString(obj);
}
if (clazz == BigDecimal.class) {
return (T) castToBigDecimal(obj);
}
if (clazz == BigInteger.class) {
return (T) castToBigInteger(obj);
}
if (clazz == Date.class) {
return (T) castToDate(obj);
}
if (clazz == java.sql.Date.class) {
return (T) castToSqlDate(obj);
}
if (clazz == java.sql.Timestamp.class) {
return (T) castToTimestamp(obj);
}
if (clazz.isEnum()) {
return (T) castToEnum(obj, clazz, config);
}
if (Calendar.class.isAssignableFrom(clazz)) {
Date date = castToDate(obj);
Calendar calendar;
if (clazz == Calendar.class) {
calendar = Calendar.getInstance(JSON.defaultTimeZone, JSON.defaultLocale);
} else {
try {
calendar = (Calendar) clazz.newInstance();
} catch (Exception e) {
throw new JSONException("can not cast to : " + clazz.getName(), e);
}
}
calendar.setTime(date);
return (T) calendar;
}
if (obj instanceof String) {
String strVal = (String) obj;
if (strVal.length() == 0 //
|| "null".equals(strVal) //
|| "NULL".equals(strVal)) {
return null;
}
if (clazz == java.util.Currency.class) {
return (T) java.util.Currency.getInstance(strVal);
}
}
throw new JSONException("can not cast to : " + clazz.getName());
}
@SuppressWarnings({ "unchecked" })
public static <T> T castToJavaBean(Map<String, Object> map, Class<T> clazz, ParserConfig config) {
try {
if (clazz == StackTraceElement.class) {
String declaringClass = (String) map.get("className");
String methodName = (String) map.get("methodName");
String fileName = (String) map.get("fileName");
int lineNumber;
{
Number value = (Number) map.get("lineNumber");
if (value == null) {
lineNumber = 0;
} else {
lineNumber = value.intValue();
}
}
return (T) new StackTraceElement(declaringClass, methodName, fileName, lineNumber);
}
{
Object iClassObject = map.get(JSON.DEFAULT_TYPE_KEY);
if (iClassObject instanceof String) {
String className = (String) iClassObject;
Class<?> loadClazz = (Class<T>) loadClass(className);
if (loadClazz == null) {
throw new ClassNotFoundException(className + " not found");
}
if (!loadClazz.equals(clazz)) {
return (T) castToJavaBean(map, loadClazz, config);
}
}
}
if (clazz.isInterface()) {
JSONObject object;
if (map instanceof JSONObject) {
object = (JSONObject) map;
} else {
object = new JSONObject(map);
}
return (T) Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(),
new Class<?>[] { clazz }, object);
}
if (config == null) {
config = ParserConfig.getGlobalInstance();
}
JavaBeanDeserializer javaBeanDeser = null;
ObjectDeserializer deserizer = config.getDeserializer(clazz);
if (deserizer instanceof JavaBeanDeserializer) {
javaBeanDeser = (JavaBeanDeserializer) deserizer;
}
if (javaBeanDeser == null) {
throw new JSONException("can not get javaBeanDeserializer");
}
return (T) javaBeanDeser.createInstance(map, config);
} catch (Exception e) {
throw new JSONException(e.getMessage(), e);
}
}
简单捋了一遍，看到代码中标黄的部分代码，可知，是利用反射原理来获得javaBean的.
如下，为Gson的demo：
1 package cn.code.gson; 2 3 import java.io.*; 4 5 import java.util.Map; 6 7 import com.google.gson.Gson; 8 import com.google.gson.GsonBuilder; 9 10 import cn.code.entity.Person; 11 12 /** 13 * Created by zq on 2017/6/16. 14 */ 15 public class GsonTest { 16 17 /** 18 * @param args 主函数形参 19 */ 20 public static void main(String[] args) { 21 Gson gson = new GsonBuilder().create(); 22 23 gson.toJson("Hello", System.out); 24 gson.toJson("123", System.out); 25 System.out.println(); 26 27 // try (Writer writer = new FileWriter("d:\\gson.txt")) { 28 // gson.toJson("Hello", writer); 29 // gson.toJson("123", writer); 30 // } catch (IOException e) { 31 // e.printStackTrace(); 32 // } 33 FileInputStream fileInputStream = null; 34 35 try { 36 fileInputStream = new FileInputStream("d:\\gson.txt"); 37 } catch (FileNotFoundException e) { 38 e.printStackTrace(); 39 } 40 41 Person person = getJavaBean(fileInputStream); 42 43 System.out.println(person); 44 } 45 46 /** 47 * 48 * @param fileInputStream 根据附件字节流 返回java类 49 * @return 50 */ 51 public static Person getJavaBean(FileInputStream fileInputStream) { 52 Gson gson = new GsonBuilder().create(); 53 Person person = null; 54 55 try (Reader reader = new InputStreamReader(fileInputStream)) { 56 person = gson.fromJson(reader, Person.class); 57 } catch (FileNotFoundException e) { 58 e.printStackTrace(); 59 } catch (IOException e) { 60 e.printStackTrace(); 61 } 62 63 return person; 64 } 65 } 66 67 68 //~ Formatted by Jindent --- http://www.jindent.com
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gson和fastjson将json对象转换成javaBean 简单对照