Java JSON Schema Generator: https://github.com/victools/jsonschema-generator

Creates JSON Schema (Draft 6, Draft 7 or Draft 2019-09) from Java classes using Jackson.

Try http://www.jsonschema2pojo.org

Or the jsonschema2pojo plug-in for Maven:

<plugin>
    <groupId>org.jsonschema2pojo</groupId>
    <artifactId>jsonschema2pojo-maven-plugin</artifactId>
    <version>1.0.2</version>
    <configuration>
        <sourceDirectory>${basedir}/src/main/resources/schemas</sourceDirectory>
        <targetPackage>com.myproject.jsonschemas</targetPackage>
        <sourceType>json</sourceType>
    </configuration>
    <executions>
        <execution>
            <goals>
                <goal>generate</goal>
            </goals>
        </execution>
    </executions>
</plugin>

The <sourceType>json</sourceType> covers the case where the sources are json (like the OP). If you have actual json schemas, remove this line.

Updated in 2014: Two things have happened since Dec '09 when this question was asked:

• The JSON Schema spec has moved on a lot. It's still in draft (not finalised) but it's close to completion and is now a viable tool specifying your structural rules

• I've recently started a new open source project specifically intended to solve your problem: jsonschema2pojo. The jsonschema2pojo tool takes a json schema document and generates DTO-style Java classes (in the form of .java source files). The project is not yet mature but already provides coverage of the most useful parts of json schema. I'm looking for more feedback from users to help drive the development. Right now you can use the tool from the command line or as a Maven plugin.

So, something like that you may have to build out yourself. However, I found that this question has been asked before. And it's been recommend to use the following resource:

http://www.jsonschema2pojo.org/

or go through the headache and build out this feature. Original: Generate Java class from JSON?