[update] JsonUtil 升级优化，增加特殊需求String的反序列化

src/main/java/com/yexuejc/base/converter/StringDeserializer.java

@@ -0,0 +1,38 @@
+package com.yexuejc.base.converter;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.JsonDeserializer;
+
+import java.io.IOException;
+
+/**
+ * <pre>
+ * json中的“”转String对象时值为null
+ * 例子：{str:""} ->
+ * JsonBean{
+ *  public String str;
+ * }
+ * str的值为null [不使用{@link StringDeserializer},str的值为“”]
+ * </pre>
+ *
+ * <pre>
+ *     使用方式：
+ *     jsonMapper.registerModule(new SimpleModule().addDeserializer(String.class, new StringDeserializer()));
+ * </pre>
+ *
+ * @author yexuejc
+ * @date 2022/10/08
+ */
+public class StringDeserializer extends JsonDeserializer<String> {
+
+    @Override
+    public String deserialize(JsonParser jsonParser, DeserializationContext deserializationContext)
+            throws IOException {
+        String timeString = jsonParser.getValueAsString();
+        if ("".equals(timeString)) {
+            return null;
+        }
+        return timeString;
+    }
+}