import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.TimeZone;
import org.apache.commons.lang3.StringEscapeUtils;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.JsonParser.Feature;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.fasterxml.jackson.databind.util.JSONPObject;
import com.fasterxml.jackson.module.jaxb.JaxbAnnotationModule;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
/**
* 简单封装Jackson，实现JSON String<->Java Object的Mapper.
* 封装不同的输出风格, 使用不同的builder函数创建实例.
*/
public class JsonMapper extends ObjectMapper {
private static final long serialVersionUID = 1L;
private static Logger logger = LoggerFactory.getLogger(JsonMapper.class);
private static JsonMapper mapper;
public JsonMapper() {
this(Include.NON_EMPTY);
}
public JsonMapper(Include include) {
// 设置输出时包含属性的风格
if (include != null) {
this.setSerializationInclusion(include);
}
// 允许单引号、允许不带引号的字段名称
this.enableSimple();
// 设置输入时忽略在JSON字符串中存在但Java对象实际没有的属性
this.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
// 空值处理为空串
this.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>(){
@Override
public void serialize(Object value, JsonGenerator jgen,
SerializerProvider provider) throws IOException,
JsonProcessingException {
jgen.writeString("");
}
});
// 进行HTML解码。
this.registerModule(new SimpleModule().addSerializer(String.class, new JsonSerializer<String>(){
@Override
public void serialize(String value, JsonGenerator jgen,
SerializerProvider provider) throws IOException,
JsonProcessingException {
jgen.writeString(StringEscapeUtils.unescapeHtml4(value));
}
}));
// 设置时区
this.setTimeZone(TimeZone.getDefault());//getTimeZone("GMT+8:00")
}
/**
* 创建只输出非Null且非Empty(如List.isEmpty)的属性到Json字符串的Mapper,建议在外部接口中使用.
*/
public static JsonMapper getInstance() {
if (mapper == null){
mapper = new JsonMapper().enableSimple();
}
return mapper;
}
/**
* 创建只输出初始值被改变的属性到Json字符串的Mapper, 最节约的存储方式，建议在内部接口中使用。
*/
public static JsonMapper nonDefaultMapper() {
if (mapper == null){
mapper = new JsonMapper(Include.NON_DEFAULT);
}
return mapper;
}
/**
* Object可以是POJO，也可以是Collection或数组。
* 如果对象为Null, 返回"null".
* 如果集合为空集合, 返回"[]".
*/
public String toJson(Object object) {
try {
return this.writeValueAsString(object);
} catch (IOException e) {
logger.warn("write to json string error:" + object, e);
return null;
}
}
/**
* 反序列化POJO或简单Collection如List<String>.
*
* 如果JSON字符串为Null或"null"字符串, 返回Null.
* 如果JSON字符串为"[]", 返回空集合.
*
* 如需反序列化复杂Collection如List<MyBean>, 请使用fromJson(String,JavaType)
* @see #fromJson(String, JavaType)
*/
public <T> T fromJson(String jsonString, Class<T> clazz) {
if (StringUtils.isEmpty(jsonString)) {
return null;
}
try {
return this.readValue(jsonString, clazz);
} catch (IOException e) {
logger.warn("parse json string error:" + jsonString, e);
return null;
}
}
/**
* 反序列化复杂Collection如List<Bean>, 先使用函數createCollectionType构造类型,然后调用本函数.
* @see #createCollectionType(Class, Class...)
*/
@SuppressWarnings("unchecked")
public <T> T fromJson(String jsonString, JavaType javaType) {
if (StringUtils.isEmpty(jsonString)) {
return null;
}
try {
return (T) this.readValue(jsonString, javaType);
} catch (IOException e) {
logger.warn("parse json string error:" + jsonString, e);
return null;
}
}
/**
* 構造泛型的Collection Type如:
* ArrayList<MyBean>, 则调用constructCollectionType(ArrayList.class,MyBean.class)
* HashMap<String,MyBean>, 则调用(HashMap.class,String.class, MyBean.class)
*/
public JavaType createCollectionType(Class<?> collectionClass, Class<?>... elementClasses) {
return this.getTypeFactory().constructParametricType(collectionClass, elementClasses);
}
/**
* 當JSON裡只含有Bean的部分屬性時，更新一個已存在Bean，只覆蓋該部分的屬性.
*/
@SuppressWarnings("unchecked")
public <T> T update(String jsonString, T object) {
try {
return (T) this.readerForUpdating(object).readValue(jsonString);
} catch (JsonProcessingException e) {
logger.warn("update json string:" + jsonString + " to object:" + object + " error.", e);
} catch (IOException e) {
logger.warn("update json string:" + jsonString + " to object:" + object + " error.", e);
}
return null;
}
/**
* 輸出JSONP格式數據.
*/
public String toJsonP(String functionName, Object object) {
return toJson(new JSONPObject(functionName, object));
}
/**
* 設定是否使用Enum的toString函數來讀寫Enum,
* 為False時時使用Enum的name()函數來讀寫Enum, 默認為False.
* 注意本函數一定要在Mapper創建後, 所有的讀寫動作之前調用.
*/
public JsonMapper enableEnumUseToString() {
this.enable(SerializationFeature.WRITE_ENUMS_USING_TO_STRING);
this.enable(DeserializationFeature.READ_ENUMS_USING_TO_STRING);
return this;
}
/**
* 支持使用Jaxb的Annotation，使得POJO上的annotation不用与Jackson耦合。
* 默认会先查找jaxb的annotation，如果找不到再找jackson的。
*/
public JsonMapper enableJaxbAnnotation() {
JaxbAnnotationModule module = new JaxbAnnotationModule();
this.registerModule(module);
return this;
}
/**
* 允许单引号
* 允许不带引号的字段名称
*/
public JsonMapper enableSimple() {
this.configure(Feature.ALLOW_SINGLE_QUOTES, true);
this.configure(Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
return this;
}
/**
* 取出Mapper做进一步的设置或使用其他序列化API.
*/
public ObjectMapper getMapper() {
return this;
}
/**
* 对象转换为JSON字符串
* @param object
* @return
*/
public static String toJsonString(Object object){
return JsonMapper.getInstance().toJson(object);
}
/**
* JSON字符串转换为对象
* @param jsonString
* @param clazz
* @return
*/
public static Object fromJsonString(String jsonString, Class<?> clazz){
return JsonMapper.getInstance().fromJson(jsonString, clazz);
}
/**
* 测试
*/
public static void main(String[] args) {
List<Map<String, Object>> list = Lists.newArrayList();
Map<String, Object> map = Maps.newHashMap();
map.put("id", 1);
map.put("pId", -1);
map.put("name", "根节点");
list.add(map);
map = Maps.newHashMap();
map.put("id", 2);
map.put("pId", 1);
map.put("name", "你好");
map.put("open", true);
list.add(map);
String json = JsonMapper.getInstance().toJson(list);
System.out.println(json);
}
}