@WebParam using javax.xml.ws.Holder

@WebService OUT params via javax.xml.ws.Holder

With SOAP it is possible to return multiple values in a single request. This is impossible in Java as a method can only return one object.

JAX-WS solves this problem with the concept of Holders. A javax.xml.ws.Holder is a simple wrapper object that can be passed into the @WebService method as a parameter. The application sets the value of the holder during the request and the server will send the value back as an OUT parameter.

Using @WebParam and javax.xml.ws.Holder

The @WebParam annotation allows us to declare the sum and multiply Holders as WebParam.Mode.OUT parameters. As mentioned, these holders are simply empty buckets the application can fill in with data to have sent to the client. The server will pass them in uninitialized.

@Stateless
@WebService(
        portName = "CalculatorPort",
        serviceName = "CalculatorService",
        targetNamespace = "http://superbiz.org/wsdl",
        endpointInterface = "org.superbiz.ws.out.CalculatorWs")
public class Calculator implements CalculatorWs {

    public void sumAndMultiply(int a, int b,
                               @WebParam(name = "sum", mode = WebParam.Mode.OUT) Holder<Integer> sum,
                               @WebParam(name = "multiply", mode = WebParam.Mode.OUT) Holder<Integer> multiply) {
        sum.value = a + b;
        multiply.value = a * b;
    }
}

If the Holders were specified as WebParam.Mode.INOUT params, then the client could use them to send data and the application as well. The Holder instances would then be initialized with the data from the client request. The application could check the data before eventually overriting it with the response values.

The WSDL

The above JAX-WS @WebService component results in the folliwing WSDL that will be created automatically. Note the sumAndMultiplyResponse complext type returns two elements. These match the @WebParam declarations and our two Holder<Integer> params.

<?xml version="1.0" encoding="UTF-8"?>
<wsdl:definitions xmlns:wsdl="http://schemas.xmlsoap.org/wsdl/"
                  name="CalculatorService"
                  targetNamespace="http://superbiz.org/wsdl"
                  xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
                  xmlns:tns="http://superbiz.org/wsdl"
                  xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <wsdl:types>
    <xsd:schema attributeFormDefault="unqualified" elementFormDefault="unqualified"
                targetNamespace="http://superbiz.org/wsdl"
                xmlns:tns="http://superbiz.org/wsdl"
                xmlns:xsd="http://www.w3.org/2001/XMLSchema">
      <xsd:element name="sumAndMultiply" type="tns:sumAndMultiply"/>
      <xsd:complexType name="sumAndMultiply">
        <xsd:sequence>
          <xsd:element name="arg0" type="xsd:int"/>
          <xsd:element name="arg1" type="xsd:int"/>
        </xsd:sequence>
      </xsd:complexType>
      <xsd:element name="sumAndMultiplyResponse" type="tns:sumAndMultiplyResponse"/>
      <xsd:complexType name="sumAndMultiplyResponse">
        <xsd:sequence>
          <xsd:element minOccurs="0" name="sum" type="xsd:int"/>
          <xsd:element minOccurs="0" name="multiply" type="xsd:int"/>
        </xsd:sequence>
      </xsd:complexType>
    </xsd:schema>
  </wsdl:types>
  <wsdl:message name="sumAndMultiplyResponse">
    <wsdl:part element="tns:sumAndMultiplyResponse" name="parameters"/>
  </wsdl:message>
  <wsdl:message name="sumAndMultiply">
    <wsdl:part element="tns:sumAndMultiply" name="parameters"/>
  </wsdl:message>
  <wsdl:portType name="CalculatorWs">
    <wsdl:operation name="sumAndMultiply">
      <wsdl:input message="tns:sumAndMultiply" name="sumAndMultiply"/>
      <wsdl:output message="tns:sumAndMultiplyResponse" name="sumAndMultiplyResponse"/>
    </wsdl:operation>
  </wsdl:portType>
  <wsdl:binding name="CalculatorServiceSoapBinding" type="tns:CalculatorWs">
    <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>
    <wsdl:operation name="sumAndMultiply">
      <soap:operation soapAction="" style="document"/>
      <wsdl:input name="sumAndMultiply">
        <soap:body use="literal"/>
      </wsdl:input>
      <wsdl:output name="sumAndMultiplyResponse">
        <soap:body use="literal"/>
      </wsdl:output>
    </wsdl:operation>
  </wsdl:binding>
  <wsdl:service name="CalculatorService">
    <wsdl:port binding="tns:CalculatorServiceSoapBinding" name="CalculatorPort">
      <soap:address location="http://127.0.0.1:4204/Calculator?wsdl"/>
    </wsdl:port>
  </wsdl:service>
</wsdl:definitions>

Testing the OUT params

Here we see a JAX-WS client executing the sumAndMultiply operation. Two empty Holder instances are created and passed in as parameters. The data from the sumAndMultiplyResponse is placed in the Holder instances and is then available to the client after the operation completes.

The holders themselves are not actually sent in the request unless they are configured as INOUT params via WebParam.Mode.INOUT on @WebParam

import org.junit.BeforeClass;
import org.junit.Test;

import javax.ejb.embeddable.EJBContainer;
import javax.xml.namespace.QName;
import javax.xml.ws.Holder;
import javax.xml.ws.Service;
import java.net.URL;
import java.util.Properties;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;

public class CalculatorTest {

    @BeforeClass
    public static void setUp() throws Exception {
        Properties properties = new Properties();
        properties.setProperty("openejb.embedded.remotable", "true");
        //properties.setProperty("httpejbd.print", "true");
        //properties.setProperty("httpejbd.indent.xml", "true");
        EJBContainer.createEJBContainer(properties);
    }

    @Test
    public void outParams() throws Exception {
        final Service calculatorService = Service.create(
                new URL("http://127.0.0.1:4204/Calculator?wsdl"),
                new QName("http://superbiz.org/wsdl", "CalculatorService"));

        assertNotNull(calculatorService);

        final CalculatorWs calculator = calculatorService.getPort(CalculatorWs.class);

        final Holder<Integer> sum = new Holder<Integer>();
        final Holder<Integer> multiply = new Holder<Integer>();

        calculator.sumAndMultiply(4, 6, sum, multiply);

        assertEquals(10, (int) sum.value);
        assertEquals(24, (int) multiply.value);
    }
}

Inspecting the messages

The above execution results in the following SOAP message.

SOAP sumAndMultiply client request

<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <ns1:sumAndMultiply xmlns:ns1="http://superbiz.org/wsdl">
      <arg0>4</arg0>
      <arg1>6</arg1>
    </ns1:sumAndMultiply>
  </soap:Body>
</soap:Envelope>

SOAP sumAndMultiplyResponse server response

<?xml version="1.0" encoding="UTF-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <ns1:sumAndMultiplyResponse xmlns:ns1="http://superbiz.org/wsdl">
      <sum>10</sum>
      <multiply>24</multiply>
    </ns1:sumAndMultiplyResponse>
  </soap:Body>
</soap:Envelope>

 Source: http://tomee.apache.org/examples-trunk/webservice-holder/README.html

How substring Method Works, Before & After JDK 7 ?

The substring(int beginIndex, int endIndex) method in JDK 6 and JDK 7 are different. Knowing the difference can help you better use them. For simplicity reasons, in the followingsubstring() represent the substring(int beginIndex, int endIndex) method.

1. What substring() does?

The substring(int beginIndex, int endIndex) method returns a string that starts with beginIndex and ends with endIndex-1.

String x = "abcdef"; x = x.substring(1,3); System.out.println(x);

Output:

bc

2. What happens when substring() is called?

You may know that because x is immutable, when x is assigned with the result of x.substring(1,3), it points to a totally new string like the following:

However, this diagram is not exactly right or it represents what really happens in the heap. What really happens when substring() is called is different between JDK 6 and JDK 7.

3. substring() in JDK 6

String is supported by a char array. In JDK 6, the String class contains 3 fields: char value[], int offset, int count. They are used to store real character array, the first index of the array, the number of characters in the String.

When the substring() method is called, it creates a new string, but the string's value still points to the same array in the heap. The difference between the two Strings is their count and offset values.

The following code is simplified and only contains the key point for explain this problem.

//JDK 6 String(int offset, int count, char value[]) { this.value = value; this.offset = offset; this.count = count; }   public String substring(int beginIndex, int endIndex) { //check boundary return new String(offset + beginIndex, endIndex - beginIndex, value); }

4. A problem caused by substring() in JDK 6

If you have a VERY long string, but you only need a small part each time by using substring(). This will cause a performance problem, since you need only a small part, you keep the whole thing. For JDK 6, the solution is using the following, which will make it point to a real sub string:

x = x.substring(x, y) + ""

5. substring() in JDK 7

This is improved in JDK 7. In JDK 7, the substring() method actually create a new array in the heap.

//JDK 7 public String(char value[], int offset, int count) { //check boundary this.value = Arrays.copyOfRange(value, offset, offset + count); }   public String substring(int beginIndex, int endIndex) { //check boundary int subLen = endIndex - beginIndex; return new String(value, beginIndex, subLen); }

Source: http://www.programcreek.com/2013/09/the-substring-method-in-jdk-6-and-jdk-7/

Difference Between String , StringBuilder and StringBuffer Classes

Difference Between String , StringBuilder and StringBuffer Classes with Example : 

Today we are going to understand the difference betweenString , StringBuilder and StringBuffer . As you will find that there are minor differences between the above mentioned classes.

String

String is immutable  ( once created can not be changed )object  . The object created as a String is stored in the  Constant String Pool  .
Every immutable object in Java is thread safe ,that implies String is also thread safe . String can not be used by two threads simultaneously.
String  once assigned can not be changed.

String  demo = " hello " ;
// The above object is stored in constant string pool and its value can not be modified.


demo="Bye" ;     //new "Bye" string is created in constant pool and referenced by the demo variable           
 // "hello" string still exists in string constant pool and its value is not overrided but we lost reference to the  "hello"string 

StringBuffer

StringBuffer is mutable means one can change the value of the object . The object created through StringBuffer is stored in the heap . StringBuffer  has the same methods as the StringBuilder , but each method in StringBuffer is synchronized that is StringBuffer is thread safe .

Due to this it does not allow  two threads to simultaneously access the same method . Each method can be accessed by one thread at a time .

But being thread safe has disadvantages too as the performance of the StringBuffer hits due to thread safe property . Thus  StringBuilder is faster than the StringBuffer when calling the same methods of each class.

StringBuffer value can be changed , it means it can be assigned to the new value . Nowadays its a most common interview question ,the differences between the above classes .
String Buffer can be converted to the string by using
toString() method.

StringBuffer demo1 = new StringBuffer("Hello") ;
// The above object stored in heap and its value can be changed .

demo1=new StringBuffer("Bye");
// Above statement is right as it modifies the value which is allowed in the StringBuffer

StringBuilder

StringBuilder  is same as the StringBuffer , that is it stores the object in heap and it can also be modified . The main difference between the StringBuffer and StringBuilder is that StringBuilder is also not thread safe. 
StringBuilder is fast as it is not thread safe . 


StringBuilder demo2= new StringBuilder("Hello");
// The above object too is stored in the heap and its value can be modified
demo2=new StringBuilder("Bye");
// Above statement is right as it modifies the value which is allowed in the StringBuilder

----------------------------------------------------------------------------------
                                    String                    StringBuffer         StringBuilder
----------------------------------------------------------------------------------                 
Storage Area | Constant String Pool           Heap                       Heap 
Modifiable     |  No (immutable)            Yes( mutable )          Yes( mutable )
Thread Safe   |           Yes                         Yes                              No
 Performance |         Fast                         Very slow                    Fast
-----------------------------------------------------------------------------------


Please mention in the comments in case you have any doubts related to the post: difference between string, stringbuffer  and stringbuilder.

Source: http://javahungry.blogspot.com/2013/06/difference-between-string-stringbuilder.html

Javax.xml.bind.JAXBContext.createUnmarshaller() Method

http://www.tutorialspoint.com/java/xml/javax_xml_bind_jaxbcontext_createunmarshaller.htm