Java 如何使用Jackson反序列化对象数组
表示Jackson支持反序列化“所有受支持类型的数组”,但我不知道具体的语法 对于单个对象,我会这样做:Java 如何使用Jackson反序列化对象数组,java,json,jackson,Java,Json,Jackson,表示Jackson支持反序列化“所有受支持类型的数组”,但我不知道具体的语法 对于单个对象,我会这样做: //json input { "id" : "junk", "stuff" : "things" } //Java MyClass instance = objectMapper.readValue(json, MyClass.class); 现在,对于阵列,我要执行以下操作: //json input [{ "id" : "junk", "stuff"
//json input
{
"id" : "junk",
"stuff" : "things"
}
//Java
MyClass instance = objectMapper.readValue(json, MyClass.class);
现在,对于阵列,我要执行以下操作:
//json input
[{
"id" : "junk",
"stuff" : "things"
},
{
"id" : "spam",
"stuff" : "eggs"
}]
//Java
List<MyClass> entries = ?
//json输入
[{
“id”:“垃圾”,
“东西”:“东西”
},
{
“id”:“垃圾邮件”,
“东西”:“鸡蛋”
}]
//爪哇
列表条目=?
有人知道是否有一个神奇的缺失命令吗?如果没有,那么解决方案是什么?首先创建一个映射器:
import com.fasterxml.jackson.databind.ObjectMapper;// in play 2.3
ObjectMapper mapper = new ObjectMapper();
作为阵列:
MyClass[] myObjects = mapper.readValue(json, MyClass[].class);
名单如下:
List<MyClass> myObjects = mapper.readValue(jsonInput, new TypeReference<List<MyClass>>(){});
List myObjects=mapper.readValue(jsonInput,newtypereference(){});
指定列表类型的另一种方法:
List<MyClass> myObjects = mapper.readValue(jsonInput, mapper.getTypeFactory().constructCollectionType(List.class, MyClass.class));
List myObjects=mapper.readValue(jsonInput,mapper.getTypeFactory().constructioncollectiontype(List.class,MyClass.class));
来自
List myObjects=Arrays.asList(mapper.readValue(json,MyClass[].class))
这个解决方案似乎对我来说是最好的。试试看{
try {
ObjectMapper mapper = new ObjectMapper();
JsonFactory f = new JsonFactory();
List<User> lstUser = null;
JsonParser jp = f.createJsonParser(new File("C:\\maven\\user.json"));
TypeReference<List<User>> tRef = new TypeReference<List<User>>() {};
lstUser = mapper.readValue(jp, tRef);
for (User user : lstUser) {
System.out.println(user.toString());
}
} catch (JsonGenerationException e) {
e.printStackTrace();
} catch (JsonMappingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
ObjectMapper mapper=新的ObjectMapper();
JsonFactory f=新的JsonFactory();
List lstUser=null;
JsonParser jp=f.createJsonParser(新文件(“C:\\maven\\user.json”);
TypeReference tRef=新的TypeReference(){};
lstUser=mapper.readValue(jp,tRef);
for(用户:lstUser){
System.out.println(user.toString());
}
}捕获(JsonGenerationException e){
e、 printStackTrace();
}捕获(JsonMappingException e){
e、 printStackTrace();
}捕获(IOE异常){
e、 printStackTrace();
}
对于一般实施:
public static <T> List<T> parseJsonArray(String json,
Class<T> classOnWhichArrayIsDefined)
throws IOException, ClassNotFoundException {
ObjectMapper mapper = new ObjectMapper();
Class<T[]> arrayClass = (Class<T[]>) Class.forName("[L" + classOnWhichArrayIsDefined.getName() + ";");
T[] objects = mapper.readValue(json, arrayClass);
return Arrays.asList(objects);
}
publicstaticlist-parseJsonArray(字符串json,
类(已定义其上的数组)
抛出IOException,ClassNotFoundException{
ObjectMapper mapper=新的ObjectMapper();
类arrayClass=(类)Class.forName(“[L”+classwhicharrayIsdefined.getName()+”;”;
T[]objects=mapper.readValue(json,arrayClass);
返回数组.asList(对象);
}
首先创建线程安全的ObjectReader实例
ObjectMapper objectMapper = new ObjectMapper();
ObjectReader objectReader = objectMapper.reader().forType(new TypeReference<List<MyClass>>(){});
ObjectMapper ObjectMapper=new ObjectMapper();
ObjectReader=objectMapper.reader().forType(新类型引用(){});
然后使用它:
List<MyClass> result = objectReader.readValue(inputStream);
List result=objectReader.readValue(inputStream);
这里有一个实用程序,用于转换json2object或Object2json,
无论您的pojo是什么(实体T)
import java.io.IOException;
导入java.io.StringWriter;
导入java.util.List;
导入com.fasterxml.jackson.core.jsongGenerationException;
导入com.fasterxml.jackson.core.JsonParseException;
导入com.fasterxml.jackson.core.type.TypeReference;
导入com.fasterxml.jackson.databind.DeserializationFeature;
导入com.fasterxml.jackson.databind.JsonMappingException;
导入com.fasterxml.jackson.databind.ObjectMapper;
导入com.fasterxml.jackson.databind.SerializationFeature;
/**
*
*@author TIAGO.MEDICI
*
*/
公共类JsonUtils{
公共静态布尔值isJSONValid(字符串jsonInString){
试一试{
最终ObjectMapper映射器=新ObjectMapper();
readTree(jsonInString);
返回true;
}捕获(IOE异常){
返回false;
}
}
公共静态字符串serializeAsJsonString(对象对象)抛出JsonGenerationException、JsonMappingException、IOException{
ObjectMapper objMapper=新的ObjectMapper();
enable(SerializationFeature.INDENT_输出);
禁用(SerializationFeature.FAIL_ON_EMPTY_bean);
StringWriter sw=新的StringWriter();
objMapper.writeValue(sw,object);
返回sw.toString();
}
公共静态字符串serializeAsJsonString(对象对象,布尔缩进)抛出JsonGenerationException、JsonMappingException、IOException{
ObjectMapper objMapper=新的ObjectMapper();
如果(缩进==真){
enable(SerializationFeature.INDENT_输出);
禁用(SerializationFeature.FAIL_ON_EMPTY_bean);
}
StringWriter StringWriter=新StringWriter();
writeValue(stringWriter,对象);
返回stringWriter.toString();
}
公共静态TJSONSTRINGTOObject(字符串内容,类clazz)抛出JsonParseException、JsonMappingException、IOException{
T obj=null;
ObjectMapper objMapper=新的ObjectMapper();
obj=objMapper.readValue(内容、类别);
返回obj;
}
@抑制警告(“原始类型”)
公共静态T JSONStringToObject数组(字符串内容)抛出JsonParseException、JsonMappingException、IOException{
T obj=null;
ObjectMapper mapper=新的ObjectMapper();
obj=mapper.readValue(内容,新类型引用(){
});
返回obj;
}
公共静态T JSONStringToObject数组(字符串内容,类clazz)抛出JsonParseException、JsonMappingException、IOException{
T obj=null;
ObjectMapper mapper=新的ObjectMapper();
mapper=new ObjectMapper().configure(反序列化功能。接受单个值作为数组,true);
obj=mapper.readValue(content,mapper.getTypeFactory().ConstructionCollectionType(List.class,clazz));
返回obj;
}
您还可以创建一个扩展ArrayList
的类:
公共静态类MyList扩展了ArrayList{}
然后像这样使用它:
List<MyClass> list = objectMapper.readValue(json, MyList.class);
List List=objectMapper.readValue(json,MyList.class);
我无法使用,因为我的过梁不允许未经检查的投射
这是一个你可以使用的替代方案。我觉得它实际上是一个更清洁的解决方案
public <T> List<T> parseJsonArray(String json, Class<T> clazz) throws JsonProcessingException {
var tree = objectMapper.readTree(json);
var list = new ArrayList<T>();
for (JsonNode jsonNode : tree) {
list.add(objectMapper.treeToValue(jsonNode, clazz));
}
return list;
}
public List parseJsonArray(字符串json,类clazz)抛出JsonProcessingException{
var-tree=objectMapper.readTree(json);
var list=new ArrayList();
for(JsonNode JsonNode:tree){
add(objectMapper.treeToValue(jsonNode,clazz));
}
退货清单;
}
List<MyClass> list = objectMapper.readValue(json, MyList.class);
public <T> List<T> parseJsonArray(String json, Class<T> clazz) throws JsonProcessingException {
var tree = objectMapper.readTree(json);
var list = new ArrayList<T>();
for (JsonNode jsonNode : tree) {
list.add(objectMapper.treeToValue(jsonNode, clazz));
}
return list;
}