我有一些
JSON进来(我没有任何控制或能力来改变JSON中的结构和/或命名…这个问题中要记住这一点很重要),它具有类似于此的“扁平”结构：
{
"name": "...","email": "...","Box_background_color": "...","Box_border_color": "...","Box_text_color": "...",...
}
现在,我可以创建一个简单的对象来保持一切平坦,如下所示：
public class Settings {
@SerializedName("name")
private String _name;
@SerializedName("email")
private String _emailAddress;
@SerializedName("Box_background_color")
private String _BoxBackgroundColor;
@SerializedName("Box_border_color")
private String _BoxBorderColor;
@SerializedName("Box_text_color")
private String _BoxTextColor;
...
}
但是,我希望与盒子设置相关的所有内容都在它自己的类中(BoxSettings).这更像我想要的：
public class Settings {
@SerializedName("name")
private String _name;
@SerializedName("email")
private String _emailAddress;
private BoxSettings _BoxSettings
...
}
public class BoxSettings {
@SerializedName("Box_background_color")
private String _BoxBackgroundColor;
@SerializedName("Box_border_color")
private String _BoxBorderColor;
@SerializedName("Box_text_color")
private String _BoxTextColor;
...
}
我知道如果JSON的结构使得盒子设置是嵌套的,那么很容易实现我想要的,但是,我没有能力改变JSON的结构,所以请不要建议(如果可以,我会这样做).
我的问题是：创建一个完整的TypeAdapter是实现我想要的唯一方法,还是我仍然可以通过注释完成大部分工作？如果不是唯一的方法,我怎么能在不改变JSON的情况下完成这个呢？
以下是“创建整个TypeAdapter”的含义示例：
public class SettingsTypeAdapter implements JsonDeserializer<Settings>,JsonSerializer<Settings> {
@Override
public JsonElement serialize(Settings src,Type typeOfSrc,JsonSerializationContext context) {
// Add _name
// Add _emailAddress
// Add BoxSettings._BoxBackgroundColor
// Add BoxSettings._BoxBorderColor
// Add BoxSettings._BoxTextColor
return jsonElement;
}
@Override
public Settings deserialize(JsonElement json,Type typeOfT,JsonDeserializationContext context) throws JsonParseException {
// Read _name
// Read _emailAddress
// Read BoxSettings._BoxBackgroundColor
// Read BoxSettings._BoxBorderColor
// Read BoxSettings._BoxTextColor
return settings;
}
}
解决方法
TypeAdapter不是唯一的方法,但在这种情况下,这是最好的方法,因为您可以将适配器与Gson实例(或您正在使用的任何库)相关联,并在那里拥有所有映射代码.
另一种方法是使用JAVA反射.我以前在我的项目中使用了以下代码的版本,但从未使用过JSON,从不使用嵌套对象(大多数时候没有其他选择,或者我想将sql结果集映射到Java对象而不调用resultSet.get … 很多时间).
这将适用于这种情况.
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Field;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import org.json.JSONObject;
public class Main {
public static void main(String[] args) {
try {
String json = "{\"name\": \"test name\",\"email\": \"email@email.com\",\"Box_background_color\": \"red\",\"Box_border_color\": \"orange\",\"Box_text_color\": \"white\",\"test3_var2\":3}";
JSONObject jsonObject = new JSONObject(json);
System.out.println(jsonObject);
System.out.println();
/*
* need to parse JSON into a map of String,Object
*/
Map<String,Object> mapAll = new HashMap<String,Object>();
Iterator<String> iter = jsonObject.keys();
while (iter.hasNext()) {
String key = (String) iter.next();
Object value = jsonObject.get(key);
mapAll.put(key,value);
System.out.println(key + "::::" + value);
}
System.out.println();
/*
* use the mapper to generate the objects
*/
MyMapper<TestClass1> myMapper = new MyMapper<TestClass1>();
TestClass1 result = myMapper.mapToObject(mapAll,TestClass1.class);
System.out.println(result);
} catch (Exception e) {
e.printStackTrace();
}
}
}
class MyMapper<T> {
@SuppressWarnings("unchecked")
public T mapToObject(Map<String,Object> flatStructure,Class<T> objectClass) {
T result = null;
Field[] fields = null;
try {
// new base object
result = objectClass.newInstance();
// get all of its fields
fields = objectClass.getDeclaredFields();
for (Field field : fields) {
// normal variable
if (field.isAnnotationPresent(MyColumn.class)) {
String variableKey = field.getAnnotation(MyColumn.class).variableKey();
setJavaFieldValue(result,field.getName(),flatStructure.get(variableKey));
}
// variable that is an object and itself has to be mapped
else if (field.isAnnotationPresent(MyInnerColumn.class)) {
String startsWith = field.getAnnotation(MyInnerColumn.class).startsWith();
// reduce the map to only have attributes that are related to this field
Map<String,Object> reducedMap = reduceMap(startsWith,flatStructure);
// make sure that there are attributes for the inner object
if (reducedMap != null) {
// map the inner object
MyMapper<T> myMapper = new MyMapper<T>();
T t2 = myMapper.mapToObject(reducedMap,(Class<T>) field.getType());
// set the mapped object to the base objecct
setJavaFieldValue(result,t2);
}
} else {
// no annotation on the field so ignored
}
}
} catch (Exception e) {
e.printStackTrace();
}
return result;
}
private Map<String,Object> reduceMap(String startsWith,Map<String,Object> mapToReduce) {
Map<String,Object> result = new HashMap<String,Object>();
for (Map.Entry<String,Object> entry : mapToReduce.entrySet()) {
if (entry.getKey().toLowerCase().startsWith(startsWith.toLowerCase())) {
result.put(entry.getKey(),entry.getValue());
}
}
return result.size() == 0 ? null : result;
}
private void setJavaFieldValue(Object object,String fieldName,Object fieldValue) {
try {
Field field = object.getClass().getDeclaredField(fieldName);
boolean fieldAccess = field.isAccessible();
// make the field accessible
field.setAccessible(true);
field.set(object,fieldValue);
// put it back to the way it was
field.setAccessible(fieldAccess);
} catch (Exception e) {
e.printStackTrace();
}
}
}
/*
* Annotation for a regular variable / field
*/
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface MyColumn {
// the variable's JSON key
String variableKey() default "";
}
/*
* Annotation for an inner / nested variable / field
*/
@Target(ElementType.FIELD)
@Retention(RetentionPolicy.RUNTIME)
@interface MyInnerColumn {
/*
* JSON keys that start with this string will be
* associated with this nested field
*/
String startsWith() default "";
}
class TestClass1 {
@MyColumn(variableKey = "name")
private String _name;
@MyColumn(variableKey = "email")
private String _emailAddress;
@MyInnerColumn(startsWith = "Box_")
private TestClass2 innerClass;
@MyInnerColumn(startsWith = "test3_")
private TestClass3 innerClass2;
@Override
public String toString() {
return "TestClass1 [_name=" + _name + ",_emailAddress=" + _emailAddress + ",innerClass=" + innerClass + ",innerClass2=" + innerClass2 + "]";
}
}
class TestClass2 {
@MyColumn(variableKey = "Box_background_color")
private String _BoxBackgroundColor;
@MyColumn(variableKey = "Box_border_color")
private String _BoxBorderColor;
@MyColumn(variableKey = "Box_text_color")
private String _BoxTextColor;
@Override
public String toString() {
return "TestClass2 [_BoxBackgroundColor=" + _BoxBackgroundColor + ",_BoxBorderColor=" + _BoxBorderColor
+ ",_BoxTextColor=" + _BoxTextColor + "]";
}
}
class TestClass3 {
@MyColumn(variableKey = "test3_var1")
private String _test3Var1;
@MyColumn(variableKey = "test3_var2")
private int _test3Var2;
@Override
public String toString() {
return "TestClass3 [_test3Var1=" + _test3Var1 + ",_test3Var2=" + _test3Var2 + "]";
}
}
产量
{"Box_background_color":"red","Box_text_color":"white","test3_var2":3,"name":"test name","email":"email@email.com","Box_border_color":"orange"}
Box_background_color::::red
Box_text_color::::white
test3_var2::::3
name::::test name
email::::email@email.com
Box_border_color::::orange
TestClass1 [_name=test name,_emailAddress=email@email.com,innerClass=TestClass2 [_BoxBackgroundColor=red,_BoxBorderColor=orange,_BoxTextColor=white],innerClass2=TestClass3 [_test3Var1=null,_test3Var2=3]]
