An SAP endpoint expects to receive a message with a message body containing an SAP request object and will return a message with a message body containing an SAP response object. SAP requests and responses are fixed map data structures containing named fields with each field having a predefined data type.

Note that the named fields in an SAP request and response are specific to an SAP endpoint, with each endpoint defining the parameters in the SAP request and response it will accept. An SAP endpoint provides factory methods to create the request and response objects that are specific to it.

public class SAPEndpoint ... {
    ...
    public Structure getRequest() throws Exception;

    public Structure getResponse() throws Exception;
    ...
}

Both SAP request and response objects are represented in Java as a structure object which supports the org.fusesource.camel.component.sap.model.rfc.Structure interface. This interface extends both the java.util.Map and org.eclipse.emf.ecore.EObject interfaces.

public interface Structure extends org.eclipse.emf.ecore.EObject,
                                        java.util.Map<String, Object> {

    <T> T get(Object key, Class<T> type);

} 

The field values in a structure object are accessed through the field’s getter methods in the map interface. In addition, the structure interface provides a type-restricted method to retrieve field values.

Structure objects are implemented in the component runtime using the Eclipse Modeling Framework (EMF) and support that framework’s EObject interface. Instances of a structure object have attached meta-data which define and restrict the structure and contents of the map of fields it provides. This meta-data can be accessed and introspected using the standard methods provided by EMF. Please refer to the EMF documentation for further details.

	Note
	Attempts to get a parameter not defined on a structure object will return null. Attempts to set a parameter not defined on a structure will throw an exception as well as attempts to set the value of a parameter with an incorrect type.

As discussed in the following sections, structure objects can contain fields that contain values of the complex field types, STRUCTURE and TABLE. Note that it is unnecessary to create instances of these types and add them to the structure. Instances of these field values are created on demand if necessary when accessed in the enclosing structure.

The fields that reside within the structure object of an SAP request or response may be either elementary or complex. An elementary field contains a single scalar value, whereas a complex field will contain one or more fields of either a elementary or complex type.

An elementary field may be either a character, numeric, hexadecimal or string field type. The following table summarizes the types of elementary fields that may reside in a structure object:

A character field contains a fixed sized character string that may use either a non-Unicode or Unicode character encoding in the underlying JCo and ABAP runtimes. Non-Unicode character strings encode one character per byte. Unicode characters strings are encoded in two bytes using UTF-16 encoding. Character field values are represented in Java as java.lang.String objects and the underlying JCo runtime is responsible for the conversion to their ABAP representation.

A character field declares its field length in its associated byteLength and unicodeByteLength properties, which determine the length of the field’s character string in each encoding system.

A numeric field contains a number. The following numeric field types are supported:

A hexadecimal field contains raw binary data. The following hexadecimal field types are supported:

A string field references a variable length string value. The length of that string value is not fixed until runtime. The storage for the string value is dynamically created in the underlying JCo and ABAP runtimes. The storage for the string field itself is fixed and contains only a string header.

A complex field may be either a structure or table field type. The following table summarizes these complex field types.

A STRUCTURE field contains a structure object and is stored in the underlying JCo and ABAP runtimes as an ABAP structure record. It corresponds to either an ABAP type u or v. The value of a STRUCTURE field is represented in Java as a structure object with the interface org.fusesource.camel.component.sap.model.rfc.Structure.

A TABLE field contains a table object and is stored in the underlying JCo and ABAP runtimes as an ABAP internal table. It corresponds to the ABAP type h. The value of the field is represented in Java by a table object with the interface org.fusesource.camel.component.sap.model.rfc.Table.

A table object is a homogeneous list data structure containing rows of structure objects with the same structure. This interface extends both the java.util.List and org.eclipse.emf.ecore.EObject interfaces.

public interface Table<S extends Structure> 
    extends org.eclipse.emf.ecore.EObject,
    java.util.List<S> {

    /**
     * Creates and adds table row at end of row list
     */
    S add();

    /**
     * Creates and adds table row at index in row list
     */
    S add(int index);

} 

The list of rows in a table object are accessed and managed using the standard methods defined in the list interface. In addition the table interface provides two factory methods for creating and adding structure objects to the row list.

Table objects are implemented in the component runtime using the Eclipse Modeling Framework (EMF) and support that framework’s EObject interface. Instances of a table object have attached meta-data which define and restrict the structure and contents of the rows it provides. This meta-data can be accessed and introspected using the standard methods provided by EMF. Please refer to the EMF documentation for further details.

	Note
	Attempts to add or set a row structure value of the wrong type will throw an exception.