import java.io.IOException; import org.apache.commons.lang.StringUtils; import org.codehaus.jackson.JsonProcessingException; import org.codehaus.jackson.map.DeserializationConfig; import org.codehaus.jackson.map.ObjectMapper; import org.codehaus.jackson.map.SerializationConfig; import org.codehaus.jackson.map.annotate.JsonSerialize.Inclusion; import org.codehaus.jackson.map.util.JSONPObject; import org.codehaus.jackson.type.JavaType; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * 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 { private static Logger logger = LoggerFactory.getLogger(JsonMapper.class); private ObjectMapper mapper; public JsonMapper(Inclusion inclusion) { mapper = new ObjectMapper(); //设置输出时包含属性的风格 mapper.setSerializationInclusion(inclusion); //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 mapper.configure(DeserializationConfig.Feature.FAIL_ON_UNKNOWN_PROPERTIES, false); //禁止使用int代表Enum的order()來反序列化Enum,非常危險 mapper.configure(DeserializationConfig.Feature.FAIL_ON_NUMBERS_FOR_ENUMS, true); } /** * 创建输出全部属性到Json字符串的Mapper. */ public static JsonMapper buildNormalMapper() { return new JsonMapper(Inclusion.ALWAYS); } /** * 创建只输出非空属性到Json字符串的Mapper. */ public static JsonMapper buildNonNullMapper() { return new JsonMapper(Inclusion.NON_NULL); } /** * 创建只输出初始值被改变的属性到Json字符串的Mapper. */ public static JsonMapper buildNonDefaultMapper() { return new JsonMapper(Inclusion.NON_DEFAULT); } /** * 创建只输出非Null且非Empty(如List.isEmpty)的属性到Json字符串的Mapper. */ public static JsonMapper buildNonEmptyMapper() { return new JsonMapper(Inclusion.NON_EMPTY); } /** * 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 mapper.writeValueAsString(object); } catch (IOException e) { logger.warn("write to json string error:" + object, e); return null; } } /** * 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. * * 如需读取集合如List/Map, 且不是List<String>这种简单类型时,先使用函數constructParametricType构造类型. * * @see #constructParametricType(Class, Class...) */ public <T> T fromJson(String jsonString, Class<T> clazz) { if (StringUtils.isEmpty(jsonString)) { return null; } try { return mapper.readValue(jsonString, clazz); } catch (IOException e) { logger.warn("parse json string error:" + jsonString, e); return null; } } /** * 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. * * 如需读取集合如List/Map, 且不是List<String>这种简单类型时,先使用函數constructParametricType构造类型. * * @see #constructParametricType(Class, Class...) */ public <T> T fromJson(String jsonString, JavaType javaType) { if (StringUtils.isEmpty(jsonString)) { return null; } try { return (T) mapper.readValue(jsonString, javaType); } catch (IOException e) { logger.warn("parse json string error:" + jsonString, e); return null; } } /** * 構造泛型的Type如List<MyBean>, * 则调用constructParametricType(ArrayList.class,MyBean.class) * Map<String,MyBean>则调用(HashMap.class,String.class, MyBean.class) */ public JavaType constructParametricType(Class<?> parametrized, Class<?>... parameterClasses) { return mapper.getTypeFactory().constructParametricType(parametrized, parameterClasses); } /** * 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. */ public <T> T update(T object, String jsonString) { try { return (T) mapper.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 void setEnumUseToString(boolean value) { mapper.configure(SerializationConfig.Feature.WRITE_ENUMS_USING_TO_STRING, value); mapper.configure(DeserializationConfig.Feature.READ_ENUMS_USING_TO_STRING, value); } /** * 取出Mapper做进一步的设置或使用其他序列化API. */ public ObjectMapper getMapper() { return mapper; } }
Jackson简单封装
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转载自liuna718-163-com.iteye.com/blog/2393210
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