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

@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; } }

其他回答

与Gson的解决方案:

Gson gson = new Gson();
JsonElement jsonElement = gson.toJsonTree(map);
MyPojo pojo = gson.fromJson(jsonElement, MyPojo.class);

杰克逊也能做到这一点。(而且自从你考虑使用jackson后,它似乎更舒服)。

使用ObjectMapper的convertValue方法:

final ObjectMapper mapper = new ObjectMapper(); // jackson's objectmapper
final MyPojo pojo = mapper.convertValue(map, MyPojo.class);

不需要转换成JSON字符串或其他东西;直接转换要快得多。

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;
    }

@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; } }
ObjectMapper objectMapper = new ObjectMapper();
// Use this if all properties are not in the class
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
final MyPojo pojo = objectMapper.convertValue(map, MyPojo.class);

与第一个答案相同,但我得到了一个错误使用,因为我不希望Map的所有属性转换为类。我还找到了objectmap .configure(反序列化特性。FAIL_ON_UNKNOWN_PROPERTIES、假);作为解决方案。