o7planning

Java XStream Tutorial

  1. What is XStream?
  2. XStream Library
  3. Quick Create a Project to work with XStream
  4. Some classes participated in the examples
  5. Converting Java object to XML
  6. Using Alias
    1. Class Aliasing
    2. Field Aliasing
    3. Implicit Collection Aliasing
    4. Attribute Aliasing
    5. Package Aliasing
  7. XStream Annotation
  8. XStream Converter

1- What is XStream?

XStream is an open source Java library, which is used to convert a Java object to an XML document and vice versa.

2- XStream Library

You can download the XStream library at:
Or declare XStream library with Maven 
<!-- http://mvnrepository.com/artifact/com.thoughtworks.xstream/xstream -->
<dependency>
    <groupId>com.thoughtworks.xstream</groupId>
    <artifactId>xstream</artifactId>
    <version>1.4.8</version>
</dependency>

3- Quick Create a Project to work with XStream

Now I quickly create a Maven project.
  • File/New/Other..
Enter:
  • Group Id: org.o7planning
  • Artifact Id: XStreamTutorial
  • Package: org.o7planning.xstreamtutorial
Declaring XStream library with Maven.
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/xsd/maven-4.0.0.xsd">
   
   <modelVersion>4.0.0</modelVersion>

   <groupId>org.o7planning</groupId>
   <artifactId>XStreamTutorial</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <packaging>jar</packaging>

   <name>XStreamTutorial</name>
   <url>http://maven.apache.org</url>

   <properties>
       <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
   </properties>

   <dependencies>
   
       <dependency>
           <groupId>junit</groupId>
           <artifactId>junit</artifactId>
           <version>3.8.1</version>
           <scope>test</scope>
       </dependency>

       <!-- http://mvnrepository.com/artifact/com.thoughtworks.xstream/xstream -->
       <dependency>
           <groupId>com.thoughtworks.xstream</groupId>
           <artifactId>xstream</artifactId>
           <version>1.4.8</version>
       </dependency>
       
   </dependencies>
   
</project>

4- Some classes participated in the examples

Address.java
package org.o7planning.xstreamtutorial.beans;

public class Address {
   
   private String street;
   private String city;

   public Address() {

   }

   public Address(String street, String city) {
       this.street = street;
       this.city = city;
   }

   public String getStreet() {
       return street;
   }

   public void setStreet(String street) {
       this.street = street;
   }

   public String getCity() {
       return city;
   }

   public void setCity(String city) {
       this.city = city;
   }

   @Override
   public String toString() {
       return street + ", " + city;
   }
   
}
Company.java
package org.o7planning.xstreamtutorial.beans;

public class Company {

   private int id;
   private String name;
   private String[] websites;
   private Address address;

   public int getId() {
       return id;
   }

   public void setId(int id) {
       this.id = id;
   }

   public String getName() {
       return name;
   }

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

   public String[] getWebsites() {
       return websites;
   }

   public void setWebsites(String[] websites) {
       this.websites = websites;
   }

   public Address getAddress() {
       return address;
   }

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

   @Override
   public String toString() {
       StringBuilder sb = new StringBuilder();

       sb.append("\n id:" + this.id);
       sb.append("\n name:" + this.name);
       if (this.websites != null) {
           sb.append("\n website: ");
           for (String website : this.websites) {
               sb.append(website + ", ");
           }
       }
       if (this.address != null) {
           sb.append("\n address:" + this.address.toString());
       }
       return sb.toString();
   }

}
DataDAO.java
package org.o7planning.xstreamtutorial;

import org.o7planning.xstreamtutorial.beans.Address;
import org.o7planning.xstreamtutorial.beans.Company;

public class DataDAO {

   
   
   public static Company createCompany() {

       Company company = new Company();
       company.setId(111);
       company.setName("Microsoft");

       String[] websites = { "http://microsoft.com",
               "http://msn.com", "http://hotmail.com" };
       company.setWebsites(websites);

       Address address = new Address();
       address.setCity("Redmond");
       address.setStreet("1 Microsoft Way");

       company.setAddress(address);

       return company;
   }
   
}

5- Converting Java object to XML

Unlike JAXB, XStream can convert a Java object to XML without a mapping, it uses a default mapping. Consider the following example:
JavaObject2Xml.java
package org.o7planning.xstreamtutorial;

import org.o7planning.xstreamtutorial.beans.Company;

import com.thoughtworks.xstream.XStream;

public class JavaObject2Xml {

   public static void main(String[] args) {
       
       Company company = DataDAO.createCompany();
       
       XStream xs = new XStream();
       
       
       // JAVA OBJECT --> XML
       String xml = xs.toXML(company);
       
       System.out.println(xml);
   }
   
   
}
Running the example: 
<org.o7planning.xstreamtutorial.beans.Company>
  <id>111</id>
  <name>Microsoft</name>
  <websites>
    <string>http://microsoft.com</string>
    <string>http://msn.com</string>
    <string>http://hotmail.com</string>
  </websites>
  <address>
    <street>1 Microsoft Way</street>
    <city>Redmond</city>
  </address>
</org.o7planning.xstreamtutorial.beans.Company>

6- Using Alias

When converting Java object into XML, By default XStream convert class name to XML tag name. Aliasing is technique to customize XML created. There are 5 types of alias: 
  1. Class Aliasing
  2. Field Aliasing
  3. Implicit Collections Aliasing
  4. Attribute Aliasing
  5. Package Aliasing

6.1- Class Aliasing

ClassAliasingExample.java
package org.o7planning.xstreamtutorial;

import org.o7planning.xstreamtutorial.beans.Company;

import com.thoughtworks.xstream.XStream;

public class ClassAliasingExample {

   public static void main(String[] args) {
       
       Company company = DataDAO.createCompany();
       
       XStream xs = new XStream();
       
       xs.alias("company", Company.class);
       
       // JAVA OBJECT --> XML
       String xml = xs.toXML(company);
       
       System.out.println(xml);
   }
   
}
Running the example: 
<company>
 <id>111</id>
 <name>Microsoft</name>
 <websites>
   <string>http://microsoft.com</string>
   <string>http://msn.com</string>
   <string>http://hotmail.com</string>
 </websites>
 <address>
   <street>1 Microsoft Way</street>
   <city>Redmond</city>
 </address>
</company

6.2- Field Aliasing

FieldAliasingExample.java
package org.o7planning.xstreamtutorial;

import org.o7planning.xstreamtutorial.beans.Company;

import com.thoughtworks.xstream.XStream;

public class FieldAliasingExample {

   public static void main(String[] args) {
       
       Company company = DataDAO.createCompany();
       
       XStream xstream = new XStream();
       
       // Class aliasing.
       xstream.alias("company", Company.class);
       
       // Field aliasing.
       // aliasField(String alias, Class definedIn, String fieldName).
       xstream.aliasField("companyName", Company.class, "name");
       xstream.aliasField("companyId", Company.class, "id");
       
       // JAVA OBJECT --> XML
       String xml = xstream.toXML(company);
       
       System.out.println(xml);
   }
   
}
Running the example: 
<company>
  <companyId>111</companyId>
  <companyName>Microsoft</companyName>
  <websites>
    <string>http://microsoft.com</string>
    <string>http://msn.com</string>
    <string>http://hotmail.com</string>
  </websites>
  <address>
    <street>1 Microsoft Way</street>
    <city>Redmond</city>
  </address>
</company>

6.3- Implicit Collection Aliasing

Usually a collection (Array/Collection) in Java when it is converted to XML it is enclosed in a tag. You can use the implicit alias for the collection to remove this tag.
ImplicitCollectionsAliasingExample.java
package org.o7planning.xstreamtutorial;

import org.o7planning.xstreamtutorial.beans.Company;

import com.thoughtworks.xstream.XStream;

public class ImplicitCollectionsAliasingExample {

   public static void main(String[] args) {
       
       Company company = DataDAO.createCompany();
       
       XStream xstream = new XStream();
       
       // Class aliasing.
       xstream.alias("company", Company.class);
       
       
       // addImplicitArray(Class ownerType, String fieldName).
       xstream.addImplicitArray(Company.class, "websites", "website");
       
       // JAVA OBJECT --> XML
       String xml = xstream.toXML(company);
       
       System.out.println(xml);

   }

}
Running the example: 
<company>
  <id>111</id>
  <name>Microsoft</name>
  <website>http://microsoft.com</website>
  <website>http://msn.com</website>
  <website>http://hotmail.com</website>
  <address>
    <street>1 Microsoft Way</street>
    <city>Redmond</city>
  </address>
</company>

6.4- Attribute Aliasing

AttributeAliasingExample.java
package org.o7planning.xstreamtutorial;

import org.o7planning.xstreamtutorial.beans.Company;

import com.thoughtworks.xstream.XStream;

public class AttributeAliasingExample {

   public static void main(String[] args) {
       
       Company company = DataDAO.createCompany();
       
       XStream xstream = new XStream();
       
       // Class aliasing.
       xstream.alias("company", Company.class);
       
       
       // useAttributeFor(Class definedIn, String fieldName).
       xstream.useAttributeFor(Company.class, "id");        
       
       xstream.useAttributeFor(Company.class, "name");
       xstream.aliasAttribute("companyName", "name");
       
       // JAVA OBJECT --> XML
       String xml = xstream.toXML(company);
       
       System.out.println(xml);

   }

}
Running the example: 
<company id="111" companyName="Microsoft">
  <websites>
    <string>http://microsoft.com</string>
    <string>http://msn.com</string>
    <string>http://hotmail.com</string>
  </websites>
  <address>
    <street>1 Microsoft Way</street>
    <city>Redmond</city>
  </address>
</company>

6.5- Package Aliasing

PackageAliasingExample.java
package org.o7planning.xstreamtutorial;

import org.o7planning.xstreamtutorial.beans.Address;
import org.o7planning.xstreamtutorial.beans.Company;

import com.thoughtworks.xstream.XStream;

public class PackageAliasingExample {

    public static void main(String[] args) {
        
        Company company = DataDAO.createCompany();
        
        XStream xstream = new XStream();  
        
        String packgeName=  Address.class.getPackage().getName();
        
        // aliasPackage(String name, String pkgName).
        xstream.aliasPackage("com.newcompany", packgeName);          
        
        
        
        // JAVA OBJECT --> XML
        String xml = xstream.toXML(company);
        
        System.out.println(xml);

    }

}
Running the example: 
<com.newcompany.Company>
  <id>111</id>
  <name>Microsoft</name>
  <websites>
    <string>http://microsoft.com</string>
    <string>http://msn.com</string>
    <string>http://hotmail.com</string>
  </websites>
  <address>
    <street>1 Microsoft Way</street>
    <city>Redmond</city>
  </address>
</com.newcompany.Company>

7- XStream Annotation

With XStream you can use the code to customize the XML generated from Java objects, in using the Alias has been mentioned above. However you can also use Annotation to tell XStream how to generate XML from Java objects.

Below is a list of Annotation:
  • @XStreamAlias
  • @XStreamAsAttribute
  • @XStreamImplicit
  • @XStreamOmitField
Using Code Using Annotation
xs.alias("dept", Department.class); @XStreamAlias("dept")
public class Department {

}
xs.aliasField("no", Department.class, "deptNo"); @XStreamAlias("no")
private int deptNo;
xs.useAttributeFor(Department.class, "deptNo") @XStreamAsAttribute
private int deptNo;
xs.omitField(Employee.class, "bonus"); @XStreamOmitField
private float bonus;
xs.addImplicitCollection(Department.class, "employees"); @XStreamImplicit
private List<Employee> employees;
Department.java
package org.o7planning.xstreamtutorial.beans;

import java.util.List;

import com.thoughtworks.xstream.annotations.XStreamAlias;
import com.thoughtworks.xstream.annotations.XStreamAsAttribute;
import com.thoughtworks.xstream.annotations.XStreamImplicit;

@XStreamAlias("dept")
public class Department {

  @XStreamAlias("no")
  @XStreamAsAttribute
  private int deptNo;

  @XStreamAlias("name")
  private String deptName;

  @XStreamImplicit
  private List<Employee> employees;

  public int getDeptNo() {
      return deptNo;
  }

  public void setDeptNo(int deptNo) {
      this.deptNo = deptNo;
  }

  public String getDeptName() {
      return deptName;
  }

  public void setDeptName(String deptName) {
      this.deptName = deptName;
  }

  public List<Employee> getEmployees() {
      return employees;
  }

  public void setEmployees(List<Employee> employees) {
      this.employees = employees;
  }

}
Employee.java
package org.o7planning.xstreamtutorial.beans;

import com.thoughtworks.xstream.annotations.XStreamAlias;
import com.thoughtworks.xstream.annotations.XStreamAsAttribute;
import com.thoughtworks.xstream.annotations.XStreamOmitField;

@XStreamAlias("emp")
public class Employee {

    @XStreamAlias("no")
    @XStreamAsAttribute
    private int empNo;
    private String empName;

    private float salary;

    // Ignore this field.
    @XStreamOmitField
    private float bonus;

    public Employee(int empNo, String empName, float salary) {
        this.empNo = empNo;
        this.empName = empName;
        this.salary = salary;
    }

    public int getEmpNo() {
        return empNo;
    }

    public void setEmpNo(int empNo) {
        this.empNo = empNo;
    }

    public String getEmpName() {
        return empName;
    }

    public void setEmpName(String empName) {
        this.empName = empName;
    }

    public float getSalary() {
        return salary;
    }

    public void setSalary(float salary) {
        this.salary = salary;
    }

    public float getBonus() {
        return bonus;
    }

    public void setBonus(float bonus) {
        this.bonus = bonus;
    }

}
XStreamAnnotationExample.java
package org.o7planning.xstreamtutorial;

import java.util.ArrayList;
import java.util.List;

import org.o7planning.xstreamtutorial.beans.Department;
import org.o7planning.xstreamtutorial.beans.Employee;

import com.thoughtworks.xstream.XStream;

public class XStreamAnnotationExample {

    public static void main(String[] args) {
        Department dept = createDepartment();

        XStream xstream = new XStream();
        
        // Using annotations in class Department
        xstream.processAnnotations(Department.class);
        
        // Using annotations in class Employee
        xstream.processAnnotations(Employee.class);
        
        String xml = xstream.toXML(dept);
        
        System.out.println(xml);
    }

    public static Department createDepartment() {
        Department dept = new Department();
        dept.setDeptNo(10);
        dept.setDeptName("ACCOUNTING");

        Employee king = new Employee(7839, "KING", 5000f);
        Employee clark = new Employee(7839, "CLARK", 2450f);
        Employee miller = new Employee(7839, "MILLER", 1300f);

        List<Employee> list = new ArrayList<Employee>();
        list.add(king);
        list.add(clark);
        list.add(miller);
        dept.setEmployees(list);
        return dept;
    }
    
}
Running the example: 
<dept no="10">
  <name>ACCOUNTING</name>
  <emp no="7839">
    <empName>KING</empName>
    <salary>5000.0</salary>
  </emp>
  <emp no="7839">
    <empName>CLARK</empName>
    <salary>2450.0</salary>
  </emp>
  <emp no="7839">
    <empName>MILLER</empName>
    <salary>1300.0</salary>
  </emp>
</dept>

8- XStream Converter

XStream Converter is the most important component in the XStream library, it is the API used to convert a Java object to an XML and vice versa. You can create a custom converter to convert between Java and XML:

  • TODO