jackson 完美用法

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import java.io.StringWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.codehaus.jackson.JsonFactory;
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.map.DeserializationConfig.Feature;
import org.codehaus.jackson.map.MappingJsonFactory;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.JavaType;
public class JsonUtils {
public static <K, V> String toJson(Map<K, V> obj) {
String jsonString = "";
try {
if (obj == null) {
return "";
}
StringWriter sw = new StringWriter();
JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);
ObjectMapper mapper = new ObjectMapper();
mapper.writeValue(gen, obj);
jsonString = sw.toString();
sw.close();
} catch (Exception ex) {
ex.printStackTrace();
return "";
}
return jsonString;
}
@SuppressWarnings("unchecked")
public static Map<String, Object> toMap(String json) {
Map<String, Object> result = new HashMap<String, Object>();
try {
if (json == null || json.equals("")) {
return null;
}
ObjectMapper objectMapper = new ObjectMapper();
result = objectMapper.readValue(json, Map.class);
if (result == null) {
return new HashMap<String, Object>();
}
} catch (Exception ex) {
ex.printStackTrace();
}
return result;
}
public static String toJson(Object object) {
String json = "";
try {
if (object == null) {
return "";
}
StringWriter sw = new StringWriter();
JsonGenerator gen = new JsonFactory().createJsonGenerator(sw);
ObjectMapper mapper = new ObjectMapper();
mapper.writeValue(gen, object);
json = sw.toString();
sw.close();
} catch (Exception ex) {
ex.printStackTrace();
json = "";
}
return json;
}
public static <T> T toObject(String json, Class<T> clazz) {
T obj = null;
try {
if (json == null || json.equals("")) {
return null;
}
JsonFactory jsonFactory = new MappingJsonFactory();
JsonParser jsonParser = jsonFactory.createJsonParser(json);
ObjectMapper mapper = new ObjectMapper();
mapper.getDeserializationConfig().set(Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
obj = mapper.readValue(jsonParser, clazz);
} catch (Exception ex) {
ex.printStackTrace();
obj = null;
}
return obj;
}
public static <T> List<T> toList(String json, Class<T> clazz) {
if (json == null || json.equals("")) {
return null;
}
ObjectMapper mapper = new ObjectMapper();
mapper.getDeserializationConfig().set(Feature.FAIL_ON_UNKNOWN_PROPERTIES, false);
List<T> list = new ArrayList<T>();
try {
JavaType type = mapper.getTypeFactory().constructParametricType(List.class, clazz);
list = mapper.readValue(json, type);
return list;
} catch (Exception e) {
e.printStackTrace();
}
return list;
}
}

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