XML Marshalling and UnMarshalling using Spring and Castor XML binding framework - Annotation Config

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What Is Spring OXM and Castor?

In enterprise Java systems, converting Java objects to XML (and vice versa) is a common requirement for integrations, messaging, and web services. Spring OXM (Object/XML Mapping) provides a clean abstraction layer over popular XML binding frameworks. Among these, the Castor XML Binding Framework is an efficient, battle-tested tool that allows developers to map complex Java objects into structured XML documents seamlessly using modern Java annotation configuration.

Marshalling vs Unmarshalling Explained

• Marshalling (Serialization): The process of converting an in-memory Java object into an XML representation (such as writing to an XML file, stream, or HTTP payload).
• Unmarshalling (Deserialization): The reverse process, taking raw XML input and converting it back into a fully populated Java object graph.
• CastorMarshaller: Spring's dedicated bean that implements both the Marshaller and Unmarshaller interfaces, acting as the bridge to Castor's engine.

Key Steps for Annotation-Based Configuration

1. Define Java Configuration (@Configuration): Create an application configuration class marked with @Configuration and @ComponentScan to eliminate legacy XML configuration files.
2. Configure the CastorMarshaller Bean: Declare a @Bean method returning CastorMarshaller and set the mapping file resource location if custom schema mapping is required.
3. Implement the Converter Service: Inject Spring's Marshaller and Unmarshaller into your service bean to execute transformations using marshal(Object, Result) and unmarshal(Source).
4. Execute via ApplicationContext: Bootstrap the container using AnnotationConfigApplicationContext to perform conversions effortlessly at runtime.

Why Use Spring with Castor?

• Clean Abstraction: Spring wraps vendor-specific checked exceptions into runtime data-access exceptions, reducing boilerplate try-catch logic.
• Modern Java Config: Utilizing pure Java annotations makes your application easier to maintain, refactor, and test.
• Flexible Integration: Seamlessly integrate XML processing with Spring Boot, Spring Batch, or Spring Integration pipelines.

Recommended Next Videos

Expand your knowledge of Spring Object/XML Mapping with these related tutorials from our channel:

• XML Marshalling and UnMarshalling Using Spring & Castor XML Binding Framework - XML Config
• Spring and JAXB Integration | Spring Object/XML Mapping | jaxb marshalling and unmarshalling
• Spring XStream Integration: Object/XML Mapping Tutorial

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XML Marshalling and UnMarshalling using Spring and Castor XML binding framework - Annotation Config

XML Marshalling and UnMarshalling using Spring and Castor XML binding framework - Annotation Config

XML Marshalling and UnMarshalling using Spring and Castor XML binding framework - Annotation Config

XML Marshalling and UnMarshalling using Spring and Castor XML binding framework - Annotation Config

XML Marshalling and UnMarshalling using Spring and Castor XML binding framework - Annotation Config

XML Marshalling and UnMarshalling using Spring and Castor XML binding framework - Annotation Config

XML Marshalling and UnMarshalling using Spring and Castor XML binding framework - Annotation Config

XML Marshalling and UnMarshalling using Spring and Castor XML binding framework - Annotation Config

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.ram.core</groupId>
    <artifactId>SpringDemo</artifactId>
    <packaging>jar</packaging>
    <version>1.0-SNAPSHOT</version>
    <name>SpringDemo</name>
    <url>http://maven.apache.org</url>

    <properties>
        <spring.version>5.1.1.RELEASE</spring.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.8.2</version>
            <scope>test</scope>
        </dependency>

        <!-- Spring 3 dependencies -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>


        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-oxm</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- Uses Castor for XML -->
        <dependency>
            <groupId>org.codehaus.castor</groupId>
            <artifactId>castor</artifactId>
            <version>1.2</version>
        </dependency>

        <!-- Castor need this -->
        <dependency>
            <groupId>xerces</groupId>
            <artifactId>xercesImpl</artifactId>
            <version>2.8.1</version>
        </dependency>

    </dependencies>
</project>

Customer.java

package com.ram.core.model;

public class Customer
{
    private String name;
    private int age;
    private String address;

    public String getName()
    {
        return name;
    }

    public void setName(String name)
    {
        this.name = name;
    }

    public int getAge()
    {
        return age;
    }

    public void setAge(int age)
    {
        this.age = age;
    }

    public String getAddress()
    {
        return address;
    }

    public void setAddress(String address)
    {
        this.address = address;
    }

    @Override
    public String toString()
    {
        return "Customer [name=" + name + ", age=" + age
                + ", address=" + address + "]";
    }

}

customer_mapping.xml

<mapping>
    <class name="com.ram.core.model.Customer">

        <map-to xml="customer" />

        <field name="name" type="string">
            <bind-xml name="name" node="element" />
        </field>

        <field name="age" type="integer">
            <bind-xml name="age" node="attribute" />
        </field>

        <field name="address" type="string">
            <bind-xml name="address" node="element" />
        </field>
    </class>
</mapping>

XMLConverter.java

package com.ram.core;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

import org.springframework.oxm.Marshaller;
import org.springframework.oxm.Unmarshaller;

public class XMLConverter
{
    private Marshaller marshaller; 
    private Unmarshaller unmarshaller;

    public Marshaller getMarshaller()
    {
        return marshaller;
    }

    public void setMarshaller(Marshaller marshaller)
    {
        this.marshaller = marshaller;
    }

    public Unmarshaller getUnmarshaller()
    {
        return unmarshaller;
    }

    public void setUnmarshaller(Unmarshaller unmarshaller)
    {
        this.unmarshaller = unmarshaller;
    }

    public void convertFromObjectToXML(Object object, String filepath)
            throws IOException
    {

        FileOutputStream os = null;
        try
        {
            os = new FileOutputStream(filepath);
            getMarshaller().marshal(object, new StreamResult(os));
        }
        finally
        {
            if (os != null)
            {
                os.close();
            }
        }
    }

    public Object convertFromXMLToObject(String xmlfile)
            throws IOException
    {
        FileInputStream is = null;
        try
        {
            is = new FileInputStream(xmlfile);
            return getUnmarshaller().unmarshal(new StreamSource(is));
        }
        finally
        {
            if (is != null)
            {
                is.close();
            }
        }
    }

}

AppConfig.java

package com.ram.core.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.oxm.castor.CastorMarshaller;

import com.ram.core.XMLConverter;

@Configuration
public class AppConfig
{

    @Bean
    public XMLConverter getHandler()
    {
        XMLConverter xmlConverter = new XMLConverter();
        xmlConverter.setMarshaller(getCastorMarshaller());
        xmlConverter.setUnmarshaller(getCastorMarshaller());
        return xmlConverter;
    }

    @Bean
    public CastorMarshaller getCastorMarshaller()
    {
        @SuppressWarnings("deprecation")
        CastorMarshaller castorMarshaller = new CastorMarshaller();
        Resource resource = new ClassPathResource(
                "customer_mapping.xml");
        castorMarshaller.setMappingLocation(resource);
        return castorMarshaller;
    }

}

castor.properties

org.exolab.castor.indent = true

App.java

package com.ram.core;

import java.io.IOException;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

import com.ram.core.config.AppConfig;
import com.ram.core.model.Customer;

public class App
{
    private static final String XML_FILE_NAME = "customer.xml";

    public static void main(String[] args) throws IOException
    {
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(
                AppConfig.class);
        XMLConverter converter = (XMLConverter) context
                .getBean(XMLConverter.class);

        Customer customer = new Customer();
        customer.setName("Peter");
        customer.setAge(52);
        customer.setAddress("A505,North Street,Bangalore");

        // from object to XML file
        converter.convertFromObjectToXML(customer, XML_FILE_NAME);
        System.out.println("Converted Object to XML!");

        // from XML to object
        Customer customer2 = (Customer) converter
                .convertFromXMLToObject(XML_FILE_NAME);
        System.out.println(customer2);
        System.out.println("Converted XML to Object!");

    }
}

Output:

Converted Object to XML!
Customer [name=Peter, age=52, address=A505,North Street,Bangalore]
Converted XML to Object!

customer.xml

<?xml version="1.0" encoding="UTF-8"?>
<customer age="52">
    <name>Peter</name>
    <address>A505,North Street,Bangalore</address>
</customer>

Click the below link to download the code:
https://sites.google.com/site/javaspringram2019/java_spring_2019/SpringDemo_Object_XML_mapping_castor_Annotation_config.zip?attredirects=0&d=1

Github Link:
https://github.com/ramram43210/Java_Spring_2019/tree/master/Spring_2019/SpringDemo_Object_XML_mapping_castor_Annotation_config

Bitbucket Link:
https://bitbucket.org/ramram43210/java_spring_2019/src/c049acad029f0a80d06bdf2c723a2d5703cecc59/Spring_2019/SpringDemo_Object_XML_mapping_castor_Annotation_config/?at=master

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