Java 对象、JSON字符串、Map、List转换

网上大部分的转换都使用阿里的fastjson，这里使用com.fasterxml.jackson.databind.ObjectMapper。

• 将对象转为JSON字符串

ObjectMapper objectMapper = new ObjectMapper();
String str = objectMapper.writeValueAsString(javaObj);

• 将JSON字符串转为Map

JavaType valueType = objectMapper.getTypeFactory()
    .constructParametricType(HashMap.class, String.class, Object.class);
HashMap<String, Object> map = objectMapper.readValue(str, valueType);

• 将JSON字符串转为List

JavaType valueType = objectMapper.getTypeFactory()
     .constructParametricType(ArrayList.class, Person.class);
List<Person> list = objectMapper.readValue(str, valueType);