该文章为原创（转载请注明出处）：申请类中的json字符串字段如何主动转换（@RequestBody、@ModelAttribute） - 简书 (jianshu.com)
应用场景
前端传值：
{ "userJson": "{\"phone\":\"123\",\"name\":\"xxx\"}"}
为了反对前端的数据结构，后端做了斗争，没法应用对本人更不便更正当的构造？
后端@RequestBody注解的类中的字段为 userJson 传输，须要在controller层手动解决
@GetMapping("test.do")public RestResponse<Void> test(@RequestBody TestBody body) { body.setUser(JSON.parseObject(body.getUserJson(), User.class)); // service.handleUser(body);}
@Datastatic class TestBody { private String userJson; private User user;}static class User { private String phone; private String name;}
如何把逻辑提取到框架或者工具层面，实现主动拆卸，无感应用对象 ？
1. 扩大Jackson的反序列化器，转换String到字段类型的对象
import com.fasterxml.jackson.core.JsonParser;import com.fasterxml.jackson.databind.*;import com.fasterxml.jackson.databind.annotation.JsonDeserialize;import com.fasterxml.jackson.databind.deser.ContextualDeserializer; import java.io.IOException; /** * @author uhfun * @see JsonDeserialize#using() */public class JacksonStringToJavaObjectDeserializer extends JsonDeserializer<Object> implements ContextualDeserializer { private JavaType javaType; @Override public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException { ObjectMapper mapper = (ObjectMapper) p.getCodec(); String value = p.getValueAsString(); return value == null ? null : mapper.readValue(value, javaType.getRawClass()); } @Override public JsonDeserializer<?> createContextual(DeserializationContext ctxt, BeanProperty property) { javaType = property.getType(); return this; }}
2. 扩大FastJson的反序列化器，转换String到字段类型的对象
import com.alibaba.fastjson.JSON;import com.alibaba.fastjson.annotation.JSONField;import com.alibaba.fastjson.parser.DefaultJSONParser;import com.alibaba.fastjson.parser.deserializer.ObjectDeserializer; import java.lang.reflect.Type; import static com.alibaba.fastjson.parser.JSONToken.LITERAL_STRING; /** * @author uhfun * @see JSONField#deserializeUsing() */public class FastJsonStringToJavaObjectDeserializer implements ObjectDeserializer { @Override public <T> T deserialze(DefaultJSONParser parser, Type type, Object fieldName) { String s = parser.parseObject(String.class); return JSON.parseObject(s, type); } @Override public int getFastMatchToken() { return LITERAL_STRING; }}
如何应用扩大的反序列化器
1. Jackson
@Datastatic class TestBody { @JsonDeserialize(using = JacksonStringToJavaObjectDeserializer.class) private User userJson;}
2. FastJson
@Datastatic class TestBody { @JSONField(deserializeUsing = FastJsonStringToJavaObjectDeserializer.class) private User userJson;}
@ModelAttribute如何反对主动绑定json字符串的字段 为 对象 ？
@GetMapping("test.do")public RestResponse<Void> test(@ModelAttribute TestBody body) { body.setUser(JSON.parseObject(body.getUserJson(), User.class)); // service.handleUser(body);}@Datastatic class TestBody { private String userJson; private User user;}static class User { private String phone; private String name;}
实现上面的切面，主动注册须要转换的转换器
import com.alibaba.fastjson.JSON;import com.alibaba.fastjson.annotation.JSONField;import com.fasterxml.jackson.databind.annotation.JsonDeserialize;import com.google.common.collect.Sets;import org.springframework.boot.autoconfigure.web.format.WebConversionService;import org.springframework.core.annotation.AnnotatedElementUtils;import org.springframework.core.annotation.AnnotationUtils;import org.springframework.core.convert.TypeDescriptor;import org.springframework.core.convert.converter.GenericConverter;import org.springframework.web.bind.WebDataBinder;import org.springframework.web.bind.annotation.ControllerAdvice;import org.springframework.web.bind.annotation.InitBinder;import org.springframework.web.bind.annotation.ModelAttribute;import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter; import java.lang.reflect.Field;import java.util.Set; import static java.util.Collections.singleton; /** * 使@ModelAttribute反对绑定Json字符串为对象 * * @author uhfun * @see RequestMappingHandlerAdapter#initControllerAdviceCache() * 寻找@ControllerAdvice切面下@InitBinder注解的办法 * @see org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#INIT_BINDER_METHODS * @see org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#getDataBinderFactory(org.springframework.web.method.HandlerMethod) * 依据切面构建InitBinderMethod办法 * @see org.springframework.web.method.annotation.InitBinderDataBinderFactory#initBinder * 初始化binder时反射调用 * @see ModelAttribute */@ControllerAdvicepublic class StringToJsonObjectSupport { private static final Set<Class<?>> CONVERTER_INITIALIZED = Sets.newConcurrentHashSet(); @InitBinder public void initStringJsonObjectConverter(WebDataBinder dataBinder) { Object target = dataBinder.getTarget(); WebConversionService conversionService; if (dataBinder.getConversionService() instanceof WebConversionService) { conversionService = (WebConversionService) dataBinder.getConversionService(); if (target != null && !CONVERTER_INITIALIZED.contains(target.getClass())) { for (Field field : dataBinder.getTarget().getClass().getDeclaredFields()) { JSONField jsonField = AnnotationUtils.findAnnotation(field, JSONField.class); boolean jsonFieldAnnotated = jsonField != null && jsonField.deserialize(), deserializeAnnotated = jsonFieldAnnotated || AnnotatedElementUtils.hasAnnotation(field, JsonDeserialize.class); if (deserializeAnnotated) { Class<?> type = field.getType(); conversionService.addConverter(new JsonStringToObjectConverter(type)); } } CONVERTER_INITIALIZED.add(target.getClass()); } } else { throw new IllegalStateException("dataBinder的ConversionService不是WebConversionService类型实例"); } } static class JsonStringToObjectConverter implements GenericConverter { private final Class<?> targetType; public JsonStringToObjectConverter(Class<?> targetType) { this.targetType = targetType; } @Override public Set<ConvertiblePair> getConvertibleTypes() { return singleton(new ConvertiblePair(String.class, targetType)); } @Override public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) { return JSON.parseObject((String) source, targetType.getType()); } }}
@Datastatic class TestBody { @JsonDeserialize private User userJson;}
该文章为原创（转载请注明出处）：申请类中的json字符串字段如何主动转换（@RequestBody、@ModelAttribute） - 简书 (jianshu.com)