How to annotate a list using @XmlElement?

Question

I have the following annotation using javax.xml.bind.annotation.XmlElement:

@XmlElement          public List<String> getKeywords() {     return keywords; } 

Which produces the following XML when I marshall some example content:

<keywords>keyword1</keywords> <keywords>keyword2</keywords> 

I would like to get the following XML:

<keywords>     <keyword>keyword1</keyword>     <keyword>keyword2</keyword> </keywords> 

What kind of an annotation should I use?

I've tried

@XmlElementWrapper @XmlElement(name="keyword") 

But then the whole content disappears and the result is:

<keywords/> 

The same happens also if I only try to rename the element:

@XmlElement(name="keyword") 

What am I doing wrong?

UPDATE:

Here is the updated full code for the class according to the first answers, but it is still not working (the result is an empty list <keywords/> when marshalled to XML):

import java.util.List; import javax.xml.bind.annotation.XmlElement; import javax.xml.bind.annotation.XmlElementWrapper; import javax.xml.bind.annotation.XmlRootElement;  @XmlRootElement public class Content {      private List<String> keywords;      public Content() {}      @XmlElementWrapper(name="keywords")     @XmlElement(name="keyword")     public List<String> getKeywords() {         return keywords;     }      public void setKeywords(List<String> keywords) {         this.keywords = keywords;     }    } 

I also tried the following with the same result:

import java.util.List; import javax.xml.bind.annotation.XmlAccessType; import javax.xml.bind.annotation.XmlAccessorType; import javax.xml.bind.annotation.XmlElement; import javax.xml.bind.annotation.XmlElementWrapper; import javax.xml.bind.annotation.XmlRootElement;  @XmlRootElement @XmlAccessorType(XmlAccessType.FIELD) public class Content {      @XmlElementWrapper(name="keywords")     @XmlElement(name="keyword")     private List<String> keywords;      public Content() {}      public List<String> getKeywords() {         return keywords;     }      public void setKeywords(List<String> keywords) {         this.keywords = keywords;     }    } 

However, the keywords are not empty as the following produces <keywords>keyword1</keywords><keywords>keyword2</keywords> instead of an empty list:

import java.util.List; import javax.xml.bind.annotation.XmlElement; import javax.xml.bind.annotation.XmlElementWrapper; import javax.xml.bind.annotation.XmlRootElement;  @XmlRootElement public class Content {      private List<String> keywords;      public Content() {}      @XmlElement     public List<String> getKeywords() {         return keywords;     }      public void setKeywords(List<String> keywords) {         this.keywords = keywords;     }    } 

The code for marshalling is (JAX-RS):

import java.io.StringWriter; import javax.ws.rs.Consumes; import javax.ws.rs.Path; import javax.ws.rs.POST; import javax.ws.rs.Produces; import javax.ws.rs.core.MediaType; import javax.ws.rs.core.Response; import javax.xml.bind.JAXBContext; import javax.xml.bind.JAXBException; import javax.xml.bind.Marshaller;  @Path("process") @Consumes(MediaType.APPLICATION_JSON) @Produces(MediaType.APPLICATION_XML) public class ContentHandler {      @POST     public Response process(Content content) {          StringWriter stringWriter = new StringWriter();         try {             JAXBContext jaxbContext = JAXBContext.newInstance(Content.class);             Marshaller jaxbMarshaller = jaxbContext.createMarshaller();             jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);             jaxbMarshaller.marshal(content, stringWriter);         } catch (JAXBException e) {             return Response.serverError().entity(e.getMessage()).build();         }         return Response.ok(stringWriter.toString(), MediaType.APPLICATION_XML).build();            }  } 

Answer 1

You need to leverage @XmlElementWrapper and @XmlElement.

Java Model

Content

import java.util.List; import javax.xml.bind.annotation.*;  @XmlRootElement public class Content {      private List<String> keywords;      public Content() {}      @XmlElementWrapper     @XmlElement(name="keyword")     public List<String> getKeywords() {         return keywords;     }      public void setKeywords(List<String> keywords) {         this.keywords = keywords;     }    } 

Demo Code

Demo

import java.util.*; import javax.xml.bind.*;  public class Demo {      public static void main(String[] args) throws Exception {         JAXBContext jc = JAXBContext.newInstance(Content.class);          List<String> strings = new ArrayList<String>(2);         strings.add("foo");         strings.add("bar");          Content content = new Content();         content.setKeywords(strings);          Marshaller marshaller = jc.createMarshaller();         marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);         marshaller.marshal(content, System.out);     }  } 

Output

<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <content>     <keywords>         <keyword>foo</keyword>         <keyword>bar</keyword>     </keywords> </content> 

For More Information

Below are links to a couple articles from my blog that provide additional information:

• http://blog.bdoughan.com/2010/09/jaxb-collection-properties.html
• http://blog.bdoughan.com/2012/12/jaxb-representing-null-and-empty.html