我一直在看杰克逊,但似乎我必须将地图转换为JSON,然后将结果JSON转换为POJO。
是否有方法将Map直接转换为POJO?
我一直在看杰克逊,但似乎我必须将地图转换为JSON,然后将结果JSON转换为POJO。
是否有方法将Map直接转换为POJO?
当前回答
如果你的类中有泛型类型,你应该使用TypeReference和convertValue()。
final ObjectMapper mapper = new ObjectMapper();
final MyPojo<MyGenericType> pojo = mapper.convertValue(map, new TypeReference<MyPojo<MyGenericType>>() {});
你也可以用它把pojo转换回java.util.Map。
final ObjectMapper mapper = new ObjectMapper();
final Map<String, Object> map = mapper.convertValue(pojo, new TypeReference<Map<String, Object>>() {});
其他回答
将Map转换为POJO的例子。注意Map键包含下划线,字段变量是驼峰。
用户阶层POJO。
import com.fasterxml.jackson.annotation.JsonProperty;
import lombok.Data;
@Data
public class User {
@JsonProperty("user_name")
private String userName;
@JsonProperty("pass_word")
private String passWord;
}
class测试这个例子
import java.util.HashMap;
import java.util.Map;
import com.fasterxml.jackson.databind.ObjectMapper;
public class App {
public static void main(String[] args) {
Map<String, String> info = new HashMap<>();
info.put("user_name", "Q10Viking");
info.put("pass_word", "123456");
ObjectMapper mapper = new ObjectMapper();
User user = mapper.convertValue(info, User.class);
System.out.println("-------------------------------");
System.out.println(user);
}
}
/**output
-------------------------------
User(userName=Q10Viking, passWord=123456)
*/
如果你的类中有泛型类型,你应该使用TypeReference和convertValue()。
final ObjectMapper mapper = new ObjectMapper();
final MyPojo<MyGenericType> pojo = mapper.convertValue(map, new TypeReference<MyPojo<MyGenericType>>() {});
你也可以用它把pojo转换回java.util.Map。
final ObjectMapper mapper = new ObjectMapper();
final Map<String, Object> map = mapper.convertValue(pojo, new TypeReference<Map<String, Object>>() {});
@Hamedz 如果使用较多的数据,则使用Jackson进行转换 光数据,使用apache… TestCase:
import java.lang.reflect.InvocationTargetException; import java.util.HashMap; import java.util.Map; import org.apache.commons.beanutils.BeanUtils; import com.fasterxml.jackson.databind.ObjectMapper; import lombok.AllArgsConstructor; import lombok.Data; import lombok.NoArgsConstructor; public class TestPerf { public static final int LOOP_MAX_COUNT = 1000; public static void main(String[] args) { Map<String, Object> map = new HashMap<>(); map.put("success", true); map.put("number", 1000); map.put("longer", 1000L); map.put("doubler", 1000D); map.put("data1", "testString"); map.put("data2", "testString"); map.put("data3", "testString"); map.put("data4", "testString"); map.put("data5", "testString"); map.put("data6", "testString"); map.put("data7", "testString"); map.put("data8", "testString"); map.put("data9", "testString"); map.put("data10", "testString"); runBeanUtilsPopulate(map); runJacksonMapper(map); } private static void runBeanUtilsPopulate(Map<String, Object> map) { long t1 = System.currentTimeMillis(); for (int i = 0; i < LOOP_MAX_COUNT; i++) { try { TestClass bean = new TestClass(); BeanUtils.populate(bean, map); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } } long t2 = System.currentTimeMillis(); System.out.println("BeanUtils t2-t1 = " + String.valueOf(t2 - t1)); } private static void runJacksonMapper(Map<String, Object> map) { long t1 = System.currentTimeMillis(); for (int i = 0; i < LOOP_MAX_COUNT; i++) { ObjectMapper mapper = new ObjectMapper(); TestClass testClass = mapper.convertValue(map, TestClass.class); } long t2 = System.currentTimeMillis(); System.out.println("Jackson t2-t1 = " + String.valueOf(t2 - t1)); } @Data @AllArgsConstructor @NoArgsConstructor public static class TestClass { private Boolean success; private Integer number; private Long longer; private Double doubler; private String data1; private String data2; private String data3; private String data4; private String data5; private String data6; private String data7; private String data8; private String data9; private String data10; } }到目前为止,使用Jackson提供的答案是很好的,但是你仍然可以有一个util函数来帮助你转换不同的pojo,如下所示:
public static <T> T convert(Map<String, Object> aMap, Class<T> t) {
try {
return objectMapper
.convertValue(aMap, objectMapper.getTypeFactory().constructType(t));
} catch (Exception e) {
log.error("converting failed! aMap: {}, class: {}", getJsonString(aMap), t.getClass().getSimpleName(), e);
}
return null;
}
与Gson的解决方案:
Gson gson = new Gson();
JsonElement jsonElement = gson.toJsonTree(map);
MyPojo pojo = gson.fromJson(jsonElement, MyPojo.class);