Java - Learn Java by Examples

How do I delete a cookie in Servlet?

By Wayan in Servlet Last modified: June 5, 2023 0 Comment

The Servlet API doesn’t provide a direct way to delete a cookie in a Servlet application. If you want to delete a cookie you have to create a cookie that have the same name with the cookie that you want to delete and set the value to an empty string. You also need to set the max age of the cookie to 0. And then add this cookie to the servlet’s response object.

Let’s see the code example below:

package org.kodejava.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(name = "DeleteCookieServlet", urlPatterns = "/deleteCookie")
public class DeleteCookieServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        //
        // To delete a cookie, we need to create a cookie that have the same
        // name with the cookie that we want to delete. We also need to set
        // the max age of the cookie to 0 and then add it to the Servlet's
        // response method.
        //
        Cookie cookie = new Cookie("username", "");
        cookie.setMaxAge(0);
        response.addCookie(cookie);
    }
}

Maven dependencies

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>4.0.1</version>
</dependency>

How to map a bean property to an XML attribute in JAXB?

By Wayan in XML Last modified: June 5, 2023 0 Comment

In this example you will learn how to define a bean’s / pojo’s properties as an XML attribute in JAXB. To define properties as an XML attribute we use the @XmlAttribute annotation. In the Student class below the id property will be defined as an attribute of the student root element. While the name and grade property will be an element of the student.

package org.kodejava.xml.support;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Student {
    private Integer id;
    private String name;
    private Integer grade;

    @XmlAttribute
    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

    public Integer getGrade() {
        return grade;
    }

    public void setGrade(Integer grade) {
        this.grade = grade;
    }
}

Here the program that we can use to convert the Student bean into an XML document.

package org.kodejava.xml;

import org.kodejava.xml.support.Student;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import java.io.FileWriter;
import java.io.IOException;

public class JAXBElementAttribute {
    public static void main(String[] args) {
        Student student = new Student();
        student.setId(1);
        student.setName("Alice");
        student.setGrade(12);

        try {
            JAXBContext context = JAXBContext.newInstance(Student.class);
            Marshaller marshaller = context.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
            marshaller.marshal(student, new FileWriter("Student.xml"));
        } catch (JAXBException | IOException e) {
            e.printStackTrace();
        }
    }
}

When you run the program a file named Student.xml will be created with the following content:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<student id="1">
    <grade>12</grade>
    <name>Alice</name>
</student>

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>javax.xml.bind</groupId>
        <artifactId>jaxb-api</artifactId>
        <version>2.3.1</version>
    </dependency>
    <dependency>
        <groupId>com.sun.xml.bind</groupId>
        <artifactId>jaxb-ri</artifactId>
        <version>2.3.5</version>
        <type>pom</type>
    </dependency>
</dependencies>

How to generate a wrapper element around XML representation in JAXB?

By Wayan in XML Last modified: June 5, 2023 2 Comments

In this example you’ll learn how to use the JAXB @XmlElementWrapper annotation. This annotation can be used to generate a wrapper element around an XML element representation. When no name defined, the @XmlElementWrapper annotation uses the property name as the wrapper element name. Let’s see the code snippet below.

Here is the code snippet for marshaling the Record object into an XML document. Before the marshalling take place, we create an object of Record and adds a some Track into it.

package org.kodejava.xml;

import org.kodejava.xml.support.Track;
import org.kodejava.xml.support.Record;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;

public class JAXBElementWrapper {
    public static void main(String[] args) {
        Track track1 = new Track();
        track1.setId(1);
        track1.setTitle("Love Me Do");

        Track track2 = new Track();
        track2.setId(2);
        track2.setTitle("From Me To You");

        Track track3 = new Track();
        track3.setId(3);
        track3.setTitle("She Loves You");

        Record record = new Record();
        record.setId(1);
        record.setTitle("The Beatles 1");
        record.getTracks().add(track1);
        record.getTracks().add(track2);
        record.getTracks().add(track3);

        try {
            JAXBContext context = JAXBContext.newInstance(Record.class);
            Marshaller marshaller = context.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
            marshaller.marshal(record, System.out);

            try (Writer writer = new FileWriter("Record.xml")) {
                marshaller.marshal(record, writer);
            }
        } catch (JAXBException | IOException e) {
            e.printStackTrace();
        }
    }
}

package org.kodejava.xml.support;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlElementWrapper;
import javax.xml.bind.annotation.XmlRootElement;
import java.util.ArrayList;
import java.util.List;

@XmlRootElement
public class Record {
    private Integer id;
    private String title;
    private String artist;
    private String genre;
    private Integer year;
    private List<Track> tracks = new ArrayList<>();

    public Record() {
    }

    @XmlAttribute
    public Integer getId() {
        return id;
    }

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

    @XmlElement
    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getArtist() {
        return artist;
    }

    public void setArtist(String artist) {
        this.artist = artist;
    }

    public String getGenre() {
        return genre;
    }

    public void setGenre(String genre) {
        this.genre = genre;
    }

    public Integer getYear() {
        return year;
    }

    public void setYear(Integer year) {
        this.year = year;
    }

    @XmlElementWrapper(name = "trackList")
    @XmlElement(name = "track")
    public List<Track> getTracks() {
        return tracks;
    }

    public void setTracks(List<Track> tracks) {
        this.tracks = tracks;
    }

    @Override
    public String toString() {
        return "Record{" +
                "title='" + title + "'\n" +
                ", artist='" + artist + "'\n" +
                ", genre='" + genre + "'\n" +
                ", year=" + year +
                '}';
    }
}

package org.kodejava.xml.support;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Track {
    private Integer id;
    private String title;

    public Track() {
    }

    public Integer getId() {
        return id;
    }

    @XmlAttribute
    public void setId(Integer id) {
        this.id = id;
    }

    @XmlElement
    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    @Override
    public String toString() {
        return "Track{" +
                "id=" + id +
                ", title='" + title + '\'' +
                '}';
    }
}

The above program will generated the following XML document.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<record id="1">
    <title>The Beatles 1</title>
    <trackList>
        <track id="1">
            <title>Love Me Do</title>
        </track>
        <track id="2">
            <title>From Me To You</title>
        </track>
        <track id="3">
            <title>She Loves You</title>
        </track>
    </trackList>
</record>

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>javax.xml.bind</groupId>
        <artifactId>jaxb-api</artifactId>
        <version>2.3.1</version>
    </dependency>
    <dependency>
        <groupId>com.sun.xml.bind</groupId>
        <artifactId>jaxb-ri</artifactId>
        <version>2.3.5</version>
        <type>pom</type>
    </dependency>
</dependencies>

How to create an XML file of a POJO using JAXB?

By Wayan in XML Last modified: June 5, 2023 0 Comment

The code snippet below show you how to convert POJO into XML file using JAXB. To do this we can pass the output file where we want the XML to be saved to the marshaller object.

package org.kodejava.xml;

import org.kodejava.xml.support.Track;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import java.io.File;

public class JAXBObjectToXmlFile {
    public static void main(String[] args) {
        Track track = new Track();
        track.setId(2);
        track.setTitle("She Loves You");

        try {
            JAXBContext context = JAXBContext.newInstance(Track.class);

            Marshaller marshaller = context.createMarshaller();
            marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

            File output = new File("Track.xml");
            marshaller.marshal(track, output);
        } catch (JAXBException e) {
            e.printStackTrace();
        }
    }
}

This snippet will create a file called Track.xml with the following content:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<track id="2">
    <title>She Loves You</title>
</track>

package org.kodejava.xml.support;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Track {
    private Integer id;
    private String title;

    public Track() {
    }

    public Integer getId() {
        return id;
    }

    @XmlAttribute
    public void setId(Integer id) {
        this.id = id;
    }

    @XmlElement
    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    @Override
    public String toString() {
        return "Track{" +
                "id=" + id +
                ", title='" + title + '\'' +
                '}';
    }
}

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>javax.xml.bind</groupId>
        <artifactId>jaxb-api</artifactId>
        <version>2.3.1</version>
    </dependency>
    <dependency>
        <groupId>com.sun.xml.bind</groupId>
        <artifactId>jaxb-ri</artifactId>
        <version>2.3.5</version>
        <type>pom</type>
    </dependency>
</dependencies>

How to convert an XML file into object using JAXB?

By Wayan in XML Last modified: June 5, 2023 0 Comment

In this code snippet you can learn how to convert or unmarshall an XML file into it corresponding POJO. The steps on unmarshalling XML to object begin by creating an instance of JAXBContext. With the context object we can then create an instance of Unmarshaller class. Using the unmarshall() method and pass an XML file will give us the target POJO as the result.

Let’s see the code snippet below:

package org.kodejava.xml;

import org.kodejava.xml.support.Track;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Unmarshaller;
import java.io.File;
import java.net.URL;
import java.util.Objects;

public class JAXBXmlToObject {
    public static void main(String[] args) {
        try {
            URL resource = JAXBXmlToObject.class.getResource("/Track.xml");
            File file = new File(Objects.requireNonNull(resource).toURI());
            JAXBContext context = JAXBContext.newInstance(Track.class);

            Unmarshaller unmarshaller = context.createUnmarshaller();
            Track track = (Track) unmarshaller.unmarshal(file);

            System.out.println("Track = " + track);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Here is the context of Track.xml:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<track id="2">
    <title>She Loves You</title>
</track>

package org.kodejava.xml.support;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Track {
    private Integer id;
    private String title;

    public Track() {
    }

    public Integer getId() {
        return id;
    }

    @XmlAttribute
    public void setId(Integer id) {
        this.id = id;
    }

    @XmlElement
    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    @Override
    public String toString() {
        return "Track{" +
                "id=" + id +
                ", title='" + title + '\'' +
                '}';
    }
}

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>javax.xml.bind</groupId>
        <artifactId>jaxb-api</artifactId>
        <version>2.3.1</version>
    </dependency>
    <dependency>
        <groupId>com.sun.xml.bind</groupId>
        <artifactId>jaxb-ri</artifactId>
        <version>2.3.5</version>
        <type>pom</type>
    </dependency>
</dependencies>