MyObject类包含常见基础类型字段和子类SubObject,SubObject包含LocalDateTime、LocalDate字段,模拟从前端接收到json字符串,然后转为对象,再把对象转为字符串。
之前有粉丝问我类里面包含内部类如何反序列化,所以这个例子也为了给粉丝一个参考。
代码片段如下,需要整个代码的请到gitee下载,文章中的测试类路径:src/test/java/com/javalaoniu/tool/JacksonMapperTest.java
@Test
public void demoTest() {
JacksonMapper instance = JacksonMapper.getInstance();
JacksonMapper jacksonMapper = JacksonMapper.nonDefaultMapper();
System.out.println(instance == jacksonMapper);
String s = "{\n" +
" \"serviceUuid\": \"9430be4f4cb244d79a5c0bf5e77136dc\", \n" +
" \"secretId\": \"dsvb942f67c43cb475\", \n" +
" \"nonceStr\": \"90907e\", \n" +
" \"sign\": \"6071BF709864F21AB1B218F3122358B4\", \n" +
" \"pageIndex\": 1, \n" +
" \"pageSize\": 100, \n" +
" \"customParams\": {\n" +
" \"startTime\": \"2019-11-19 14:42:47\",\n" +
" \"endDate\": \"2019-11-20\",\n" +
" \"itemCodes\": \"90000700100754196914440306,90000600100754196914440309,90000800100754196914440306," +
"90000700100754196914440342\"\n" +
" }\n" +
"}";
MyObject myObject = JacksonMapper.fromJsonString(s, MyObject.class);
logger.info(myObject.toString());
String json = instance.toJson(myObject);
logger.info(json);
}
实体类
/**
* 静态内部类,jackson解析内部类时需要static修饰,否则需要把类单独放到java文件中
*
* @JsonFormat 来自定义时间格式
* @JsonIgnore可以忽略某个 Java 对象中的属性,它将不参与 JSON 的序列化与反序列化
* @JsonGetter可以在对 Java 对象进行 JSON 序列化时自定义属性名称
* @JsonSetter可以在对 JSON 进行反序列化时设置 JSON 中的 key 与 Java 属性的映射关系
*/
static class MyObject {
private String serviceUuid;
private String secretId;
private String nonceStr;
private String sign;
private Integer pageIndex;
private Integer pageSize;
private SubObject customParams;
。。。。。get/set等代码
}
/**
* 静态内部类,jackson解析内部类时需要static修饰,否则需要把类单独放到java文件中
*
* @JsonSerialize 指定序列化使用的类
* @JsonDeserialize 指定反序列化使用的类
*/
static class SubObject {
@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")
@JsonDeserialize(using = LocalDateTimeDeserializer.class)
@JsonSerialize(using = LocalDateTimeSerializer.class)
private LocalDateTime startTime;
@JsonFormat(pattern = "yyyy-MM-dd")
@JsonDeserialize(using = LocalDateDeserializer.class)
@JsonSerialize(using = LocalDateSerializer.class)
private LocalDate endDate;
private String itemCodes;
。。。。。get/set等代码
}
jackson工具类
package com.javalaoniu.tool.utils;
import com.fasterxml.jackson.annotation.JsonInclude.Include;
import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonParser.Feature;
import com.fasterxml.jackson.core.JsonProcessingException;
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.util.JSONPObject;
import com.fasterxml.jackson.module.jaxb.JaxbAnnotationModule;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.util.TimeZone;
/**
* 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 JacksonMapper extends ObjectMapper {
private static final long serialVersionUID = 1L;
private static Logger logger = LoggerFactory.getLogger(JacksonMapper.class);
private static JacksonMapper mapper;
private JacksonMapper() {
this(Include.NON_EMPTY);
}
private JacksonMapper(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);
// 运行empty的属性
this.disable(SerializationFeature.FAIL_ON_EMPTY_BEANS);
// 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("");
}
});
//this.registerModule(new SimpleModule().addSerializer(new MyBigDecimalDesirializer()));
// 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")
}
/**
* 设定是否使用Enum的toString函数来读写Enum,
* 为False时使用Enum的name()函数来 读写Enum, 默认为False.
* 注意本函数一定要在Mapper创建后, 所有的读写动作之前调用.
*/
public JacksonMapper 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 JacksonMapper 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 JacksonMapper enableSimple() {
this.configure(Feature.ALLOW_SINGLE_QUOTES, true);
this.configure(Feature.ALLOW_UNQUOTED_FIELD_NAMES, true);
this.configure(SerializationFeature.WRITE_BIGDECIMAL_AS_PLAIN,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;
}
/**
* 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 (jsonString==null || jsonString.isEmpty()) {
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>, 先使用函数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 (jsonString==null || jsonString.isEmpty()) {
return null;
}
try {
return (T) this.readValue(jsonString, javaType);
} catch (IOException e) {
logger.warn("parse json string error:" + jsonString, e);
return null;
}
}
/**
* 构造泛型的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);
}
/**
* 当JSON里只含有Bean的部分属性时,更新一个已存在Bean,只覆盖该部分的属性.
*/
@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;
}
/**
* 输出JSONP格式数据.
*/
public String toJsonP(String functionName, Object object) {
return toJson(new JSONPObject(functionName, object));
}
/**
* 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 JacksonMapper getInstance() {
if (mapper == null){
mapper = new JacksonMapper(Include.ALWAYS).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 JacksonMapper nonDefaultMapper() {
if (mapper == null){
mapper = new JacksonMapper(Include.NON_DEFAULT);
}
return mapper;
}
/**
* 封装这个方法便于直接类名调用
* 对象转换为JSON字符串
* @param object
* @return
*/
public static String toJsonString(Object object){
return JacksonMapper.getInstance().toJson(object);
}
/**
* 封装这个方法便于直接类名调用
* JSON字符串转换为对象
* @param jsonString
* @param clazz
* @return
*/
public static <T> T fromJsonString(String jsonString, Class<T> clazz){
return JacksonMapper.getInstance().fromJson(jsonString, clazz);
}
}
maven依赖
<jackson.version>2.16.0</jackson.version>
<!--jackson-module-jaxb-annotations 依赖jackson-databind、jackson-core、jackson-annotations,
所以可以只显示地添加jackson-module-jaxb-annotations依赖,
jackson-databind、jackson-core、jackson-annotations 也随之添加到 Java 项目工程中-->
<dependency>
<groupId>com.fasterxml.jackson.module</groupId>
<artifactId>jackson-module-jaxb-annotations</artifactId>
<version>${jackson.version}</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jsr310</artifactId>
<version>${jackson.version}</version>
</dependency>