B.1 Meta-data format

Configuration meta-data files are located inside jars under META-INF/spring-configuration-metadata.json They use a simple JSON format with items categorized under either “groups” or “properties” and additional values hint categorized under "hints":

{"groups": [
    {
        "name": "server",
        "type": "org.springframework.boot.autoconfigure.web.ServerProperties",
        "sourceType": "org.springframework.boot.autoconfigure.web.ServerProperties"
    },
    {
        "name": "spring.jpa.hibernate",
        "type": "org.springframework.boot.autoconfigure.orm.jpa.JpaProperties$Hibernate",
        "sourceType": "org.springframework.boot.autoconfigure.orm.jpa.JpaProperties",
        "sourceMethod": "getHibernate()"
    }
    ...
],"properties": [
    {
        "name": "server.port",
        "type": "java.lang.Integer",
        "sourceType": "org.springframework.boot.autoconfigure.web.ServerProperties"
    },
    {
        "name": "server.servlet-path",
        "type": "java.lang.String",
        "sourceType": "org.springframework.boot.autoconfigure.web.ServerProperties",
        "defaultValue": "/"
    },
    {
          "name": "spring.jpa.hibernate.ddl-auto",
          "type": "java.lang.String",
          "description": "DDL mode. This is actually a shortcut for the \"hibernate.hbm2ddl.auto\" property.",
          "sourceType": "org.springframework.boot.autoconfigure.orm.jpa.JpaProperties$Hibernate"
    }
    ...
],"hints": [
    {
        "name": "spring.jpa.hibernate.ddl-auto",
        "values": [
            {
                "value": "none",
                "description": "Disable DDL handling."
            },
            {
                "value": "validate",
                "description": "Validate the schema, make no changes to the database."
            },
            {
                "value": "update",
                "description": "Update the schema if necessary."
            },
            {
                "value": "create",
                "description": "Create the schema and destroy previous data."
            },
            {
                "value": "create-drop",
                "description": "Create and then destroy the schema at the end of the session."
            }
        ]
    }
]}

Each “property” is a configuration item that the user specifies with a given value. For example server.port and server.servlet-path might be specified in application.properties as follows:

server.port=9090
server.servlet-path=/home

The “groups” are higher level items that don’t themselves specify a value, but instead provide a contextual grouping for properties. For example the server.port and server.servlet-path properties are part of the server group.

	Note
It is not required that every “property” has a “group”, some properties might just exist in their own right.

Finally, “hints” are additional information used to assist the user in configuring a given property. When configuring the spring.jpa.hibernate.ddl-auto property, a tool can use it to offer some auto-completion help for the none, validate, update, create and create-drop values.

B.1.1 Group Attributes

The JSON object contained in the groups array can contain the following attributes:

B.1.2 Property Attributes

The JSON object contained in the properties array can contain the following attributes:

The JSON object contained in the deprecation attribute of each properties element can contain the following attributes:

	Note
Prior to Spring Boot 1.3, a single deprecated boolean attribute can be used instead of the deprecation element. This is still supported in a deprecated fashion and should no longer be used. If no reason and replacement are available, an empty deprecation object should be set.

Deprecation can also be specified declaratively in code by adding the @DeprecatedConfigurationProperty annotation to the getter exposing the deprecated property. For instance, let’s assume the app.foo.target property was confusing and was renamed to app.foo.name

_@ConfigurationProperties("app.foo")_
public class FooProperties {

    private String name;

    public String getName() { ... }

    public void setName(String name) { ... }

    _@DeprecatedConfigurationProperty(replacement = "app.foo.name")_
    _@Deprecated_
    public String getTarget() {
        return getName();
    }

    _@Deprecated_
    public void setTarget(String target) {
        setName(target);
    }
}

The code above makes sure that the deprecated property still works (delegating to the name property behind the scenes). Once the getTarget and setTarget methods can be removed from your public API, the automatic deprecation hint in the meta-data will go away as well.

B.1.3 Hint Attributes

The JSON object contained in the hints array can contain the following attributes:

The JSON object contained in the values attribute of each hint element can contain the following attributes:

The JSON object contained in the providers attribute of each hint element can contain the following attributes:

B.1.4 Repeated meta-data items

It is perfectly acceptable for “property” and “group” objects with the same name to appear multiple times within a meta-data file. For example, you could bind two separate classes to the same prefix, with each potentially offering overlap of property names. While this is not supposed to be a frequent scenario, consumers of meta-data should take care to ensure that they support such scenarios.