jackson工具类json转list、json转map、json转bean、bean转json

import java.io.IOException;
import java.util.List;
import java.util.Map;

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

/**
* Json工具类，基于Jackson实现
*
* @author Val Song
* @date Sep 4, 2017
*
*/
public class JacksonUtils {

/**
* 将对象转化成json
*
* @param t
* @return
* @throws JsonProcessingException
*/
public static <T> String toJson(T t) throws JsonProcessingException {
return OBJECT_MAPPER.get().writeValueAsString(t);
}

/**
* 将json转化成bean
*
* @param json
* @param valueType
* @return
* @throws JsonParseException
* @throws JsonMappingException
* @throws IOException
*/
public static <T> T toEntity(String json, Class<T> valueType)
throws JsonParseException, JsonMappingException, IOException {
return OBJECT_MAPPER.get().readValue(json, valueType);
}

/**
* 将json转化成List
*
* @param json
* @param collectionClass
* @param elementClass
* @return
* @throws JsonParseException
* @throws JsonMappingException
* @throws IOException
*/
public static <T> List<T> toList(String json, Class<? extends List> collectionClass, Class<T> elementClass)
throws JsonParseException, JsonMappingException, IOException {
JavaType javaType = OBJECT_MAPPER.get().getTypeFactory().constructCollectionType(collectionClass, elementClass);
return OBJECT_MAPPER.get().readValue(json, javaType);
}

/**
* 将json转化成Map
*
* @param json
* @param mapClass
* @param keyClass
* @param valueClass
* @return
* @throws JsonParseException
* @throws JsonMappingException
* @throws IOException
*/
public static <K, V> Map<K, V> toMap(String json, Class<? extends Map> mapClass, Class<K> keyClass,
Class<V> valueClass) throws JsonParseException, JsonMappingException, IOException {
JavaType javaType = OBJECT_MAPPER.get().getTypeFactory().constructMapType(mapClass, keyClass, valueClass);
return OBJECT_MAPPER.get().readValue(json, javaType);
}

// ################################################################################################################

/**
* 禁止调用无参构造
*
* @throws IllegalAccessException
*/
private JacksonUtils() throws IllegalAccessException {
throw new IllegalAccessException("Can't create an instance!");
}

/**
* 使用ThreadLocal创建对象，防止出现线程安全问题
*/
private static final ThreadLocal<ObjectMapper> OBJECT_MAPPER = new ThreadLocal<ObjectMapper>() {
@Override
protected ObjectMapper initialValue() {
ObjectMapper objectMapper = new ObjectMapper();
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false); // 忽略不存在的字段
return objectMapper;
}
};

}