Introduction
Generating XML Schema Definitions (XSD) from Java classes is a common requirement when working with JAXB in Java-based applications. By using the JAXB-2 Maven Plugin, you can simplify this process and automate schema generation directly within your Maven projects. This guide walks you through the setup, configuration, and execution to generate XSD files efficiently from annotated Java classes.
We will use JAXB-2 Maven Plugin in a Maven project to generate XSD from Java classes.
JAXB2 Maven Plugin uses JAXB SchemaGenerator utility to generate XSD from Java classes. Java classes should have JAXB annotations to be used by this plugin. Minimum Java version required is Java 5.
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Setting up the Maven Project
First, create a new Maven project. You can give any name, group ID, and artifact ID you want. Once we build our project, it will generate XSD classes in the
target/generated-resources/schemagen directory. After build, our project structure will look like the image below.
Final pom.xml File
Here is the final pom.xml file we have:
<project xmlns="https://maven.apache.org/POM/4.0.0" xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="https://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>jaxb-schemagen</groupId>
<artifactId>jaxb-schemagen</artifactId>
<version>0.0.1-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>javax.xml.bind</groupId>
<artifactId>jaxb-api</artifactId>
<version>2.1</version>
</dependency>
</dependencies>
<build>
<pluginManagement>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.5.1</version>
</plugin>
</plugins>
</pluginManagement>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>jaxb2-maven-plugin</artifactId>
<version>1.5</version>
<executions>
<execution>
<id>schemagen</id>
<goals>
<goal>schemagen</goal>
</goals>
</execution>
</executions>
<configuration>
<transformSchemas>
<transformSchema>
<uri>https://www.example.org/employee</uri>
<toPrefix>empns</toPrefix>
<toFile>employee.xsd</toFile>
</transformSchema>
<transformSchema>
<uri>https://www.example.org/address</uri>
<toPrefix>addrns</toPrefix>
<toFile>address.xsd</toFile>
</transformSchema>
</transformSchemas>
<includes>
<include>com/journaldev/bean/*</include>
</includes>
<verbose>true</verbose>
</configuration>
</plugin>
</plugins>
</build>
</project>Java Classes
Here are the Java classes we have that will be used to generate XSD:
Employee.java
package com.journaldev.bean;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlType;
@XmlType(namespace = "https://www.example.org/employee")
public class Employee {
private String name;
private int id;
private String role;
private Address address;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@XmlAttribute
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getRole() {
return role;
}
public void setRole(String role) {
this.role = role;
}
public Address getAddress() {
return address;
}
public void setAddress(Address address) {
this.address = address;
}
}Address.java
package com.journaldev.bean;
import javax.xml.bind.annotation.XmlType;
@XmlType(namespace = "https://www.example.org/address")
public class Address {
private String city;
private int zip;
private String addressLine1;
private String addressLine2;
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public int getZip() {
return zip;
}
public void setZip(int zip) {
this.zip = zip;
}
public String getAddressLine1() {
return addressLine1;
}
public void setAddressLine1(String addressLine1) {
this.addressLine1 = addressLine1;
}
public String getAddressLine2() {
return addressLine2;
}
public void setAddressLine2(String addressLine2) {
this.addressLine2 = addressLine2;
}
}Generated XSD Files
Our project setup is ready. Just build the project using the command mvn clean install, and the XSD files will be generated.
employee.xsd
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema xmlns:xs="https://www.w3.org/2001/XMLSchema" targetNamespace="https://www.example.org/address" version="1.0">
<xs:complexType name="address">
<xs:sequence>
<xs:element minOccurs="0" name="addressLine1" type="xs:string"/>
<xs:element minOccurs="0" name="addressLine2" type="xs:string"/>
<xs:element minOccurs="0" name="city" type="xs:string"/>
<xs:element name="zip" type="xs:int"/>
</xs:sequence>
</xs:complexType>
</xs:schema>address.xsd
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<xs:schema xmlns:xs="https://www.w3.org/2001/XMLSchema" xmlns:addrns="https://www.example.org/address" targetNamespace="https://www.example.org/employee" version="1.0">
<xs:import namespace="https://www.example.org/address" schemaLocation="address.xsd"/>
<xs:complexType name="employee">
<xs:sequence>
<xs:element minOccurs="0" name="address" type="ns1:address"/>
<xs:element minOccurs="0" name="name" type="xs:string"/>
<xs:element minOccurs="0" name="role" type="xs:string"/>
</xs:sequence>
<xs:attribute name="id" type="xs:int" use="required"/>
</xs:complexType>
</xs:schema>Conclusion
Generating XSD from Java classes using the JAXB-2 Maven Plugin is a straightforward and efficient process. By following the steps outlined above, you can automate schema creation and maintain consistency in your XML data structures. This approach is highly beneficial for projects that require frequent updates to schemas or rely on strongly typed XML interactions. We hope this guide makes your schema generation process simpler and more reliable.
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