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This article mainly explains "how to map the list in YAML to Java List". The content in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "how to map the list in YAML to Java List".

1. Overview

In this short tutorial, we will learn more about how to map YAML lists to lists in Spring Boot.

Let's start with some background on how to define lists in YAML. Then, we'll take a closer look at how to bind an YAML list to an object list.

two。 Take a quick look at the list in YAML

In short, YAML is a human-readable data serialization standard that provides a concise and clear way to write configuration files. The advantage of YAML is that it supports multiple data types, such as list, mapping, and scalar types.

The elements in the YAML list are defined with the "-" character, and they share the same indentation level:

Yamlconfig:

List:

-item1

-item2

-item3

-item4

Compared with properties:

Yamlconfig.list [0] = item1

Yamlconfig.list [1] = item2

Yamlconfig.list [2] = item3

Yamlconfig.list [3] = item4

In fact, the hierarchy of YAML significantly enhances readability compared to properties files. Another interesting feature of YAML is the ability to define different properties for different Spring profiles.

It is worth mentioning that Spring bootstrapping provides out-of-the-box support for YAML configuration. By design, the Spring boot loads configuration properties from the application. Yml starts without any extra work.

3. Bind a YAML list to a simple list of objects

Spring Boot provides @ ConfigurationProperties annotations to simplify the logic of mapping external configuration data to the object model.

In this section, we will use @ ConfigurationProperties to bind a YAML list to list.

Let's first define a simple list in application.yml:

Application:

Profiles:

-dev

-test

-prod

-1

-2

Then, we will create a simple ApplicationProps POJO to hold the logic for binding the YAML list to the object list:

@ Component

@ ConfigurationProperties (prefix = "application")

Public class ApplicationProps {

Private List profiles

/ / getter and setter

}

The ApplicationProps class needs to be decorated with @ ConfigurationProperties to express the intention to map all YAML attributes with the specified prefix to the ApplicationProps object.

To bind the profiles list, we only need to define a field of type list, and the rest is processed by the @ ConfigurationProperties annotation.

Notice that we use @ Component to register the ApplicationProps class as a normal Spring bean. Therefore, we can inject it into other classes in the same way as any other Spring bean.

Finally, we inject ApplicationProps bean into a test class and verify that our profile YAML list is correctly injected as list:

@ ExtendWith (SpringExtension.class)

@ ContextConfiguration (initializers = ConfigFileApplicationContextInitializer.class)

@ EnableConfigurationProperties (value = ApplicationProps.class)

Class YamlSimpleListUnitTest {

@ Autowired

Private ApplicationProps applicationProps

@ Test

Public void whenYamlList_thenLoadSimpleList () {

AssertThat (applicationProps.getProfiles () .get (0)) .isEqualTo ("dev")

AssertThat (applicationProps.getProfiles (). Get (4). GetClass ()) .isEqualTo (Integer.class)

AssertThat (applicationProps.getProfiles (). Size ()) .isEqualTo (5)

}

4. Bind a YAML list to a complex list

Now, let's take a closer look at how to inject nested YAML lists into complex structured lists.

First, let's add some nested lists to application.yml:

Application:

/ /...

Props:

-

Name: YamlList

Url: http://yamllist.dev

Description: Mapping list in Yaml to list of objects in Spring Boot

-

Ip: 10.10.10.10

Port: 8091

-

Email: support@yamllist.dev

Contact: http://yamllist.dev/contact

Users:

-

Username: admin

Password: admin@10@

Roles:

-READ

-WRITE

-VIEW

-DELETE

-

Username: guest

Password: guest@01

Roles:

-VIEW

In this example, we bind the prop property to a List. Similarly, we will map users to a list of User objects.

However, in the case of the user, all items share the same key, so to simplify its mapping, we may need to create a dedicated user class that encapsulates the key as a field:

Public class ApplicationProps {

/ /...

Private List props

Private List users

/ / getters and setters

Public static class User {

Private String username

Private String password

Private List roles

/ / getters and setters

}

}

Now let's verify that the nested YAML list is mapped correctly:

@ ExtendWith (SpringExtension.class)

@ ContextConfiguration (initializers = ConfigFileApplicationContextInitializer.class)

@ EnableConfigurationProperties (value = ApplicationProps.class)

Class YamlComplexListsUnitTest {

@ Autowired

Private ApplicationProps applicationProps

@ Test

Public void whenYamlNestedLists_thenLoadComplexLists () {

AssertThat (applicationProps.getUsers (). Get (0). GetPassword ()) .isEqualTo ("admin@10@")

AssertThat (applicationProps.getProps (). Get (0). Get ("name"). IsEqualTo ("YamlList")

AssertThat (applicationProps.getProps (). Get (1). Get ("port"). GetClass () .isEqualTo (Integer.class)

}

} Thank you for reading, the above is the content of "how to map the list in YAML to Java List". After the study of this article, I believe you have a deeper understanding of how to map the list in YAML to Java List, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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