杰克逊从类创建JavaType [英] Jackson create JavaType from Class

问题描述

必须有一种方法可以从String.class创建JavaType吗?

There must be a way to create a JavaType from String.class?

注意:在我的用例中，方法的输入必须 JavaType，因为该值是使用TypeFactory动态创建的.

Note: The input for the method must be JavaType for my use case because that value is created dynamically using TypeFactory.

/** Returns a JavaType for Map<String, valueType> **/
private static JavaType stringToJavaType(JavaType valueType) {
    TypeFactory typeFactory = objectMapper.getTypeFactory();
    // this does not compile, can't mix Class and JavaType
    return typeFactory.constructMapType(Map.class, String.class, valueType);
}

如果我想回答一个相关问题，相对于constructParametricType，constructMapType有什么优势?

If I may tack on a related question, what is the advantage of constructMapType over constructParametricType?

推荐答案

您可以通过以下方式实现:

You can do it by:

• constructFromCanonical 方法.例如:typeFactory.constructFromCanonical(String.class.getName())
• constructArrayType 方法.例如:typeFactory.constructArrayType(String.class).getContentType().但这看起来有点像变通办法.
• SimpleType.constructUnsafe 方法.例如:SimpleType.constructUnsafe(String.class).文档中的注释:杰克逊核心类使用的方法:不能由应用程序代码使用:它不能正确处理超类型的检查，因此父类和已实现的接口都无法通过生成的类型实例进行访问.因此，甚至可以尝试使用它来避免这种情况.

• constructFromCanonical method. For example: typeFactory.constructFromCanonical(String.class.getName())
• constructType method. For example: typeFactory.constructType(new TypeReference<String>() {}).
• constructArrayType method. For example: typeFactory.constructArrayType(String.class).getContentType(). But it looks a little bit like a workaround.
• SimpleType.constructUnsafe method. For example: SimpleType.constructUnsafe(String.class). Note from documentation: Method used by core Jackson classes: NOT to be used by application code: it does NOT properly handle inspection of super-types, so neither parent Classes nor implemented Interfaces are accessible with resulting type instance. So, even it is possible to use try to avoid it.

这篇关于杰克逊从类创建JavaType的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！