[英]How to deserialize JSON string to enum
我的 JSON 如下所示:
{
"name": "john",
"options": {
"test": 1,
"operation": "op1", // I need to deserialize this option to enum.
...
// any number of options
}
}
我的課程如下所示:
public class Info {
public String name;
@JsonTypeInfo(use = JsonTypeInfo.Id.NONE)
public Map<String, Object> options;
}
public enum OperationEnum {OP1, OP2, OP3}
如何反序列化為options
映射operation
如enum
和test
到Integer
您應該可以使用@JsonAnySetter
來幫助您:
public class Info {
public static class Options {
public int test;
public OperationEnum operation;
}
public String name;
public Options options;
private final Map<String, Object> properties = new HashMap<>();
@JsonAnySetter
public void add(String key, String value) {
properties.put(key, value);
}
}
public enum OperationEnum {OP1, OP2, OP3}
這里有一篇很好的文章: https : //www.concretepage.com/jackson-api/jackson-jsonanygetter-and-jsonanysetter-example
為什么不這樣做:
public class Info {
public static class Options {
public int test;
public OperationEnum operation;
}
public String name;
public Options options;
}
public enum OperationEnum {OP1, OP2, OP3}
那么它應該是 JustWork!
JSON 結構,其中所有選項(不同類型)都像Map<String, Object> options;
一樣存儲Map<String, Object> options;
強制執行額外的解析,因為值類型是基於標簽識別的(如"operation"
和OperationEnum
類)這里有 2 種使用ObjectMapper.readValue
和Enum.valueOf
如果可能,請考慮更靈活的解決方案,例如來自@Matthew 的解決方案
class Demo {
public static void main(String[] args) throws Exception {
ObjectMapper om = new ObjectMapper();
Info info = om.readValue(jsonValue, Info.class);
OperationEnum operationM = om.readValue("\"" + info.options.get("operation") + "\"", OperationEnum.class);
System.out.println(operationM);
OperationEnum operationE = OperationEnum.valueOf(info.options.get("operation").toString());
System.out.println(operationE);
}
static String jsonValue = "{\n" +
" \"name\": \"john\",\n" +
" \"options\": {\n" +
" \"test\": 1,\n" +
" \"operation\": \"OP1\" \n" +
" }\n" +
"}";
}
簡單的解決方案是用一個類包裝Map
實例,並為每個非常規屬性實現額外的方法。 您可以使用@JsonAnySetter
注釋來存儲所有key-value
對。
見下面的例子:
import com.fasterxml.jackson.annotation.JsonAnySetter;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.Map;
public class JsonOptionsWithCustomEnumApp {
public static void main(String[] args) throws IOException {
File jsonFile = new File("./resource/test.json").getAbsoluteFile();
ObjectMapper mapper = new ObjectMapper();
Info info = mapper.readValue(jsonFile, Info.class);
Options options = info.getOptions();
System.out.println(options.toMap());
System.out.println(options.getOperation());
}
}
class Info {
private String name;
private Options options;
//getters, setters
}
class Options {
private Map<String, Object> values = new LinkedHashMap<>();
@JsonAnySetter
private void setValues(String key, Object value) {
values.put(key, value);
}
public OperationEnum getOperation() {
Object operation = values.get("operation");
if (operation == null) {
return null;
}
return Arrays.stream(OperationEnum.values())
.filter(op -> op.name().equalsIgnoreCase(operation.toString()))
.findFirst()
.orElse(null);
}
public Map<String, Object> toMap() {
return values;
}
}
enum OperationEnum {OP1, OP2, OP3}
上面的代碼打印:
{test=1, operation=op1}
OP1
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