1. Introduction

1.导言

While working with Jackson, we might face situations where we’ll have to produce a JavaType from the given Class object.

在使用 Jackson 时、的情况下，我们可能需要生成一个 JavaType 从给定的 Class 对象中生成。</span

In this tutorial, we’ll see how to create a JavaType from a Class with the aid of Jackson library.

在本教程中，我们将了解如何借助 Jackson 库从 Class 创建 JavaType。<br

2. Introduction to JavaType and Class

2.JavaType 和 Class 简介

Before getting into details, let’s glance at JavaType and Class.

在了解细节之前、让我们浏览一下JavaType 和 Class.</span

2.1. The JavaType in Java

2.1.Java 中的 JavaType

In Jackson, the JavaType class represents Java types. It is a mechanism that enables working with generic types, such as parameterized types and arrays.

在杰克逊、JavaType 类代表 Java 类型。它是一种机制，可用于处理通用类型，例如参数化类型和数组。

Creating the JavaType instance is important, especially when we are processing generic structures during the JSON handling.

创建JavaType实例非常重要，尤其是当我们在处理 JSON 时处理泛型结构时。实例非常重要，尤其是当我们在处理 JSON 时处理通用结构时。

2.2. The Class in Java

2.2.Java 中的类</span

In Java, the Class class is a member of the reflection API and is used at runtime to represent a class or interface.

在Java中、 Class 类是反射 API 的成员，在运行时用于表示类或接口。</span

Moreover, it offers the class information, including its name, fields, methods, and constructors.

此外，它还提供类信息，包括名称、字段、方法、和构造函数。 <br

3. Using TypeFactory to Create JavaType

3.使用 TypeFactory 创建 JavaType</em

To generate a JavaType instance from a provided Class object using Jackson, we harness the TypeFactory class.

要使用 Jackson 从提供的 Class 对象生成 JavaType实例、我们利用 TypeFactory 类。</span

The TypeFactory provides a default instance, and as such, we can construct different types, whether generic or parameterized.

TypeFactory 提供了默认实例、因此，我们可以构建不同的类型，无论是通用类型还是参数化类型。

自动调整程序的参数。

Let’s take an example using TypeFactory to generate a JavaType object from a generic class:

让我们以使用 TypeFactory从一个泛型类生成一个JavaType对象：</span

class MyGenericClass<T> {
    // Class Implementation
}

@Test
void givenGenericClass_whenCreatingJavaType_thenJavaTypeNotNull() {
    Class<?> myClass = MyGenericClass.class;

    JavaType javaType = TypeFactory.defaultInstance().constructType(myClass);

    assertNotNull(javaType);
}

Here, we first define a Class object named myClass, representing the generic class MyGenericClass.

在这里，我们首先定义一个 Class 对象，名为myClass 、代表泛型类 MyGenericClass。

Then, we use the constructType() method to create a JavaType instance based on the provided Class object (myClass).

然后、我们使用constructType()方法创建一个JavaType实例，该实例基于提供的类对象 (myClass)。。

In addition, we use the assertNotNull() assertion to ensure that the JavaType instance is successfully created, validating the correctness of the process.

此外、我们使用 assertNotNull()断言来确保JavaType 实例已成功创建、验证过程的正确性。</span

4. Handling Parameterized Types

4.处理参数化类型

To smoothly build upon our knowledge of JavaType creation, we’ll see working with parameterized types with the TypeFactory class.

顺利地积累我们的JavaType创建知识、我们将了解如何使用参数化类型来处理类型工厂类。</span

Additionally, this will be based on the section that we have just discussed, which talks about the generation of JavaType instances for generic classes.

此外，这将基于我们刚才讨论的部分、JavaType泛型类实例的生成。

Let’s see an example:

让我们来看一个例子：

class Container<T> {
    // Class Implementation
}

@Test
void givenParametricType_whenCreatingJavaType_thenJavaTypeNotNull() {
    Class<?> containerClass = Container.class;
    Class<?> elementType = String.class;

    JavaType javaType = TypeFactory.defaultInstance().constructParametricType(containerClass, elementType);

    assertNotNull(javaType);
}

In this case, we have a Container parameterized class with String elements. Moreover, an instance of JavaType is created with the constructParametricType() method representing the parameterized type.

在这种情况下，我们有一个带有 String 元素的 Container 参数化类。此外、 一个 JavaType的实例是用 创建的。SpellingErrorV2Themed SCXW59581134 BCX0″>constructParametricType()方法代表参数化类型。参数化类型。

The assertion is also used to verify that the JavaType object is successfully created, hence the routine of handling parameterized type is correct.

断言还用于验证JavaType 对象已成功创建、因此处理参数化类型的例程是正确的。

5. Conclusion

5.结论

In this tutorial, we learned how to build instances of JavaType from Class objects with the help of the Jackson library.

在本教程中，我们学习了如何借助 Jackson 库从 Class 对象构建 JavaType 的实例。

As always, the source code for the examples is available over on GitHub.

一如既往，示例的源代码可从 GitHub 上获取。