I have the following code and I need to output a json object with key value pairs.
public enum General implements Catalogue {
TOUR("3D Tour"),
VIDEOS("Videos"),
PHOTOS_ONLY("Photos Only"),
PRICE_REDUCED("Price Reduced"),
FURNISHED("Furnished"),
LUXURY("Luxury");
private final String value;
General(String value) {
this.value = value;
}
public String getValue() {
return value;
}
public static List<String> valuesList() {
return Arrays.stream(General.values()).map(General::getValue).collect(Collectors.toList());
}
}
My response should be like this
This method inside your Enum will return General jsonArray alone. You need to construct the final json on top of it.
public static List<Map<String, String>> jsonList() {
return Arrays.stream(General.values()).map(e -> {
Map<String, String> m = new HashMap<>();
m.put("text", e.name());
m.put("value", e.getValue());
return m;
}).collect(Collectors.toList());
}
Having pojo class with text & value will be good one, instead of putting in map.
public class GeneralPojo {
private String text;
private String value;
public GeneralPojo(String text, String value) {
this.text = text;
this.value = value;
}
public String getText() {
return text;
}
public void setText(String text) {
this.text = text;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
If using the above Pojo, then your method should be
public static List<GeneralPojo> jsonObjList() {
return Arrays.stream(General.values()).map(e -> new GeneralPojo(e.name(), e.getValue()))
.collect(Collectors.toList());
}
Related
I'm writing annotated model classes for json serialization/deserialization using jackson.
I have a json that contains a map, where the key is an enum and the value can be different types (including arrays) depending on key value.
A simplified example, this is what I need:
{
"key1": "string value",
"key2": [{"id":"1", "value": "test1"}, {"id":"2", "value": "test2"}]
}
I have tried, and I get this:
{
"KEY1": {"value": "string value"},
"KEY2": {"list": [{"id": "1", "value": "test1"}, {"id": "2", "value": "test2"}]}
}
So, unwrapping does not work.
Could anyone tell me what I am doing wrong ?
Here is the code:
public class Main {
public static void main(String[] args) throws Exception {
HashMap<Keys, ValueType> map = new HashMap<>();
map.put(Keys.KEY1, new StringValue("string value"));
map.put(Keys.KEY2, new ListValue( Arrays.asList(new Element[] {
new Element("1", "test1"),
new Element("2", "test2")
} )));
ObjectMapper objectMapper = new ObjectMapper();
String s = objectMapper.writeValueAsString(map);
System.out.println(s);
}
}
public enum Keys {
KEY1("key1"),
KEY2("key2");
private String value;
Keys(String s) {
this.value = s;
}
}
public interface ValueType {
}
public class StringValue implements ValueType {
#JsonUnwrapped
private String value;
public StringValue(String value) {
this.value = value;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
public class ListValue implements ValueType {
#JsonUnwrapped
private List<Element> list;
public ListValue(List<Element> list) {
this.list = list;
}
public List<Element> getList() {
return list;
}
public void setList(List<Element> list) {
this.list = list;
}
}
public class Element {
#JsonProperty
private String id;
#JsonProperty
private String value;
public Element(String id, String value) {
this.id = id;
this.value = value;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
You can annotate the classes' getters methods with the JsonValue annotation that indicates that the value of annotated accessor is to be used as the single value to serialize for the instance, instead of the usual method of collecting properties of value:
public class StringValue implements ValueType {
#JsonUnwrapped
private String value;
public StringValue(String value) {
this.value = value;
}
#JsonValue //<-- added annotation to the original getter method
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
public class ListValue implements ValueType {
#JsonUnwrapped
private List<Element> list;
public ListValue(List<Element> list) {
this.list = list;
}
#JsonValue //<-- added annotation to the original getter method
public List<Element> getList() {
return list;
}
public void setList(List<Element> list) {
this.list = list;
}
}
The json structure is the following:
{
"key":"Key",
"value":{
"first": "first",
"second": "second"
}
}
I want using Spring Boot get this json as Plain Old Java Object.
public class File {
private String key;
private JsonObject value;
public File(String key, JsonObject value) {
this.key = key;
this.value = value;
}
public File() {
}
public String getKey() {
return key;
}
public void setKey(String key) {
this.key = key;
}
public JsonObject getValue() {
return value;
}
public void setValue(JsonObject value) {
this.value = value;
}
}
JsonObject - the class from lib com.google.gson
I am getting {}
It would be perfect to get field "value" as String but JsonObject is okay too.
Done! It's possible with com.google.json lib using setter:
public class File {
private String key;
private String value;
public File() {
}
public String getKey() {
return key;
}
public void setKey(String key) {
this.key = key;
}
public String getValue() {
return value;
}
public void setValue(Object value) {
this.value = new Gson().toJson(value);
}
}
I was asked to make a a column called Type a varchar2(1)which has values partial or all
That what i made in Model.Java
#Column(name="TYPE")
#Enumerated(EnumType.STRING)
public TypeEnum getType() {
return type;
}
public void setType(TypeEnum type) {
this.type = type;
}
And this is my TypeEnum.java
public enum TypeEnum {
ALL(0, "all"),
PARTIAL(1, "partial");
private int code;
private String value;
private TypeEnum(int code, String value) {
this.code = code;
this.value = value;
}
public String getValue() {
return value;
}
public int getCode() {
return code;
}
public static TypeEnum getTypeEnum(String value){
TypeEnum[] types = values();
for(int i=0; i<types.length; i++){
TypeEnum type = types[i];
if(value.equals(type.getValue()))
return type;
}
return null;
}
}
So how to store the TypeEnum in DB to achieve the varchar2(1)
You could use a Converter to map your enums to varchar(1) yourself. Something like:
#Column("TYPE") #Convert(TypeEnumToString.class) TypeEnum type;
with the converter class implemented something like:
public class TypeEnumToString implements AttributeConverter<TypeEnum, String> {
#Override
public TypeEnum convertToEntityAttribute(String value) {
// return conversion;
}
#Override
public String convertToDatabaseColumn(TypeEnum value) {
// return conversion;
}
}
You can achieve this by implementing AttributeConverter<TypeEnum, String>
#Converter
public class TypeEnumConverter implements AttributeConverter<TypeEnum, String> {
#Override
public String convertToDatabaseColumn(TypeEnum attribute) {
return String.valueOf(attribute.getCode());
}
#Override
public TypeEnum convertToEntityAttribute(String dbData) {
return getTypeEnumFromCode(parseInt(dbData));
}
}
getTypeEnumFromCode can be implemented similar to your getTypeEnum method.
Then, define it like
#Column("TYPE")
#Convert(TypeEnumToString.class)
TypeEnum type;
p.s.I just used code from your enum but it can be any other logic too.
I have a CustomObject declared as raw type of <T>. And when I populate a List<CustomObject> with new instances of it, I can't get them back as a CustomObject, only as an Object.
public class CustomObject<T> {
private String name;
private T value;
// getters and setters
}
But obviously when I use subclass, all is working as expecting;
public class CustomObject {
private class SubCustomObject<T> {
private String name;
private T value;
}
public CustomObject() {
this.customObject = new SubCustomObject();
private SubCustomObject customObject;
// getters and setters
}
Is there a way to make the first example to behave like the second one, and avoid using extra object and so I could do this:
public class CustomObject<T> {
private String name;
private T value;
private boolean isGroup;
// getters and setters
private void setValue(T value) {
if (value instanceof String) {
this.value = value;
this.isGroup = false;
}
if (value instanceof CustomObject) {
if (isGroup()) {
((List<CustomObject>) this.value).add((CustomObject) value);
} else {
this.value = (T) new ArrayList<CustomObject>();
this.isGroup = true;
setValue(value);
}
}
}
}
public void getItemByName(String name) {
// say the list is already populated
for (CustomObject object : listOfCustomObject) {
String nameField = object.getName();
if (name.equals(nameField) {
System.out.println(nameField);
}
}
}
Instead of this one:
public void getItemByName(String name) {
// say the list is already populated
for (Object object : listOfCustomObject) {
String nameField = ((CustomObject)object).getName();
if (name.equals(nameField) {
System.out.println(nameField);
}
}
}
// Apply that behavior to this and avoid to use inner class.
public class MetadataEntry {
public MetadataEntry() {
this.entity = new Entry();
}
private class Entry<T> {
private String name;
private T value;
private boolean isGroup;
private void setValue(T value) {
if (value instanceof String) {
this.value = value;
this.isGroup = false;
}
if (value instanceof MetadataEntry) {
if (isGroup()) {
((List<MetadataEntry>) this.value).add((MetadataEntry) value);
} else {
this.value = (T) new ArrayList<MetadataEntry>();
this.isGroup = true;
setValue(value);
}
}
}
}
private Entry entity;
public void setName(String name) {
this.entity.name = name;
}
public String getName() {
return this.entity.name;
}
public void setValue(String value) {
entity.setValue(value);
}
public void setValue(MetadataEntry value) {
entity.setValue(value);
}
public boolean isGroup() {
return this.entity.isGroup;
}
public List<MetadataEntity> getChildNodes() {
if (isGroup()) {
return (List<MetadataEntry>) this.entity.value;
}
return null;
}
public String getValue() {
if (!isGroup()) {
return (String) this.entity.value;
}
return null;
}
}
You can not make a list of different types X,Y,Z and put it in a single container of type W. You need to define a bounding parameter on your raw type so that your items and list are of same type. probably your T should be bounded by some interface type or it should extends some class.
Here’s my suggestion. I have abandoned the generics. Instead of just one inner class there is now an abstract inner class with two subclasses, one for groups and one for entries that are not groups. The good news: no cast is necessary anywhere.
public class MetadataEntry {
private String name;
static abstract class Entry {
abstract Entry setValue(String value);
abstract Entry setValue(MetadataEntry value);
abstract boolean isGroup();
abstract List<MetadataEntry> getChildNodes();
abstract String getSimpleValue();
}
static class SimpleEntry extends Entry {
private String value;
public SimpleEntry(String value) {
this.value = value;
}
#Override
Entry setValue(String value) {
this.value = value;
return this;
}
#Override
Entry setValue(MetadataEntry value) {
return new GroupEntry(value);
}
#Override
public boolean isGroup() {
return false;
}
#Override
public List<MetadataEntry> getChildNodes() {
return null;
}
#Override
public String getSimpleValue() {
return value;
}
}
static class GroupEntry extends Entry {
List<MetadataEntry> value;
public GroupEntry(MetadataEntry value) {
this.value = new ArrayList<>();
this.value.add(value);
}
#Override
Entry setValue(String value) {
return new SimpleEntry(value);
}
#Override
Entry setValue(MetadataEntry value) {
this.value.add(value);
return this;
}
#Override
public boolean isGroup() {
return true;
}
#Override
public List<MetadataEntry> getChildNodes() {
return value;
}
#Override
public String getSimpleValue() {
return null;
}
}
private Entry entity;
public void setName(String name) {
this.name = name;
}
public String getName() {
return this.name;
}
public void setValue(String value) {
entity = entity.setValue(value);
}
public void setValue(MetadataEntry value) {
entity = entity.setValue(value);
}
public boolean isGroup() {
return this.entity.isGroup();
}
public List<MetadataEntry> getChildNodes() {
return entity.getChildNodes();
}
public String getValue() {
return entity.getSimpleValue();
}
}
I have used an idea similar to what m 1987 said about a class that returns an instance of itself. I applied it to the inner classes only to free the users of the outer class from caring about this trickery. If you prefer, I am sure it could be applied to the outer class instead. Then you would have an abstrat class on the outer level with two subclasses, and would no longer need the inner classes. This is one of the things you asked for, so you may prefer it, but it comes at a cost: anyone calling setValue() on the outer class would need to remember that they got a new instance back.
I have a CustomObject declared as raw type of <T>.
That doesn't makes sense. You either have a raw type or a generic, not a raw type of a generic.
And when I populate a List with new instances of it, I can't get them back as a CustomObject, only as an Object.
Because your list is not generic (always bad). When you declare a List<Something> it will return Something on a get call. That Something can be generic or a raw type. A List<CustomObject<String>> will not accept a CustomObject<Integer> and using the raw type List<CustomObject> will end in disaster, hence the danger in raw types.
Now let's look at your code. The class
public class CustomObject<T> {
private String name;
private T value;
}
defines an object that behaves the same for any type. In essence what you have here is just a glorified Object with a String serving as its name attached to it.
However, now you do
private void setValue(T value) {
if (value instanceof String)
// ...
if (value instanceof CustomObject)
// ...
}
which separates the behavior for different types. and what happens if the generic type is not a String or a CustomObject?
Let's try to solve your problem. Since generics are meant to unify the behavior, let's look at what the unified behavior is that you're trying to get:
public void getItemByName(String name) {
for (CustomObject object : listOfCustomObject) {
String nameField = object.getName();
// ...
}
}
}
Basically, you require that all the items in listOfCustomObject implement a String getName() method. That's it as far as I can see from your question. That means that your CustomObject<T> should either implement an interface or extend a class (call it Superthing) with that method. Then you will just declare your list as List<? extends Superthing>.
As for the CustomObject itself, it doesn't need to be generic as you hint that there are only 2 types of generics you want to deal with (you have 2 ifs, but no else to deal with a general case). It looks like what you want are 2 different classes with different behaviors that both implement or extend a common supertype.
Try something like this:
abstract class AbstractEntry {
private String name;
protected boolean isGroup;
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public boolean isGroup() {
return isGroup;
}
}
class MetaEntry extends AbstractEntry {
AbstractEntry value;
MetaEntry(AbstractEntry value) {
this.value = value;
// handle isGroup
}
public void setValue(AbstractEntry value) {
this.value = value;
}
public AbstractEntry getValue() {
if (!isGroup)
return value;
return null;
}
}
class StringEntry extends AbstractEntry {
String value;
StringEntry(String value) {
this.value = value;
isGroup = false;
}
public void setValue(String value) {
this.value = value;
}
public String getValue() {
return value;
}
}
I think there is no need of list as it always hold only one element. As #Ole V.V mentioned, the requirement naturally calls for the use of composition and in fact, generic does not fit into your requirements. Here is how I would tackle your requirements:
public interface Named {
public String getName();
public String getValue();
}
public class CustomObject implements Named {
private String name;
private String value;
private boolean isGroup;
// getters and setters
private boolean isGroup() {
return isGroup;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
public class CustomObject2 implements Named {
private String name;
private CustomObject value;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getValue() {
return value.getValue();
}
public void setValue(CustomObject value) {
this.value = value;
}
}
public class DriverCustomObject {
public static void main(String arg[]) {
CustomObject t = new CustomObject();
t.setName("key1");
t.setValue("value1");
CustomObject2 t2 = new CustomObject2();
t2.setName("complex");
t2.setValue(t);
List<Named> list = new ArrayList<Named>();
list.add(t);
list.add(t2);
for (Named l : list) {
System.out.println(l.getName());
System.out.println(l.getValue());
}
}
}
While converting JSON data to POJO using Gson I get this error.
com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was STRING
at line 1 column 119
My JSON is :
{
"success":true,
"result":[
{
"htmlId":"edit_text_1",
"value":"3",
"contentType":"Snippet"
},
{
"htmlId":"edit_text_2",
"value":[
{
"type":"HTML",
"value":"<ul>\n<li>This is a text from the static editable content.</li>\n</ul>"
},
{
"type":"Text",
"value":"- This is a text from the static editable content."
} ],
"contentType":"Text"
}
]
}
for each result the value type may differ. Sometimes it is a string value or an array.
Here's my pojo for results:
private String htmlId;
private Object value = new ArrayList<Object>();
private String contentType;
public String getHtmlId() {
return htmlId;
}
public void setHtmlId(String htmlId) {
this.htmlId = htmlId;
}
public Object getValue() {
return value;
}
public void setValue(Object value) {
if(value instanceof String)
this.value = (List<String>)value;
else if(value instanceof ArrayList)
this.value = (ArrayList<MarketoTypeValue>)value;
}
public String getContentType() {
return contentType;
}
public void setContentType(String contentType) {
this.contentType = contentType;
}
When there is no snippet type in the result, my code works fine.
Tried with typecast, that did not help me either.
What can be the best way to handle such scenario?
First define a value class
class Value {
private String type;
private String value;
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
}
Then update your big root pojo
class Pojo {
private String htmlId;
private Collection<Value> valuea;
private String contentType;
public String getHtmlId() {
return htmlId;
}
public void setHtmlId(String htmlId) {
this.htmlId = htmlId;
}
public Collection<Value> getValuea() {
return valuea;
}
public void setValuea(Collection<Value> valuea) {
this.valuea = valuea;
}
public String getContentType() {
return contentType;
}
public void setContentType(String contentType) {
this.contentType = contentType;
}
}
And convert it using Gson
GsonBuilder builder = new GsonBuilder();
Gson gson = builder.create();
final Collection<Pojo> collection = gson.fromJson(json, Collection.class);