3.3 Generating Code from Schema

For a given schema, HydraExpress generates C++ classes, HTML API documentation, and a sample application. HydraExpress also generates makefiles for building the C++ classes and the sample application. By default, HydraExpress places the output into a new code generation directory based on the provided project name.

To use the HydraExpress code generator with the Purchase Order schema, po.xsd:

1. Set up your environment, following the instructions in Chapter 2, "Installation," in the HydraExpress User's Guide.

2. Go to the directory installdir\tutorials\xmlbinding\basic\.

3. Invoke the HydraExpress code generator, using the command shown below.

rwsfgen example-project.xml 

The HydraExpress project file example-project.xml directs the compiler rwsfgen to generate a project named basicExample, based on the po.xsd schema, with the whitespace=true option. (The project name is required, provided either as a command line option (-projectname projectname) or in the HydraExpress project file.)

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The HydraExpress project file example-project.xml includes all options and files to be used as an argument to the code generator, so using this file results in exactly the same generated code as providing the options and files directly. For more information on the use of HydraExpress project files in the shipped examples, see Section 1.5.1, "The Use of the HydraExpress Project File in Shipped Examples," in the HydraExpress User's Guide.

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For complete information about the command-line options, see Section 21.6, "Generator Options," in the HydraExpress Web Service Development Guide.

HydraExpress generates a C++ class for each complex type, top-level element, and sequence or choice defined in the XML Schema. Table 3 shows the schema definitions and the corresponding classes.

Table 1: Classes generated for po.xsd schema 

The item anonymous complex type takes its name from the enclosing element, and the resulting class name reflects the fact that the element is nested within the Items complex type. For a complete description of how schema definitions get reflected in the generated code, see Chapter 8, "Mapping XML Schema to C++."

The generator creates many additional files to support the XML data binding, including marshaling classes, makefiles, a sample application, and HTML documentation. For a complete listing, see Section 3.3.3 below.

Files are separated into several subdirectories according to type, as shown below.

  basicExample/
     app/ 
        data
     codegen/
        data
     docs/
     include/
        <projectname>
            <namespace>

The directory app contains the sample application, and the directory include contains relevant include and header files organized by project name and then by namespace, if the schema includes one. The directory codegen contains the source files for the datatype and marshaling classes, and it contents should not be modified. The docs directory contains HTML documentation. Single-click access is provided through the index.html file in the docs directory.

For more information on the code generation directory structure, see Section 22.3, "The Code Generation Directory," in the HydraExpress Web Service Development Guide.

To use the sample application located in the directory basicExample\apps\data, add your application logic to it. For the purposes of this example, you'll use instead the provided implemented application, po_main.cpp, located in the directory installdir\tutorials\xmlbinding\basic.

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Source code other than those in the app directory is not overwrite protected. You should never add business logic or make any other changes to the generated source code as these changes will be lost the next time the code is generated.

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Table 2 lists the generated files for the Basic example.

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Files that are overwrite-protected are generated with a ".sample" extension if a file exists in the code generation directory of the same name. See Section 21.7, "Overwrite Protection," in the HydraExpress Web Service Development Guide

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Table 2: Generated files for an XML Schema 

basicExample\

basicExample.xml

makefile
makefile_debug

basicExample.dsp or
basicExample.sln

make.include 

deployDebug.bat deployRelease.bat

    app\

makefiles
MSVC project files

        data\

po_main.cpp or
po_main.cpp.sample

    codegen\

makefiles
MSVC project files

        data\

makefiles
MSVC project files

            po\

Items.cpp 
ItemsItem.cpp
PurchaseOrder.cpp
PurchaseOrderType.cpp
USAddress.cpp

[poStatics.cpp]

ItemsMarshal.cpp
ItemsItemMarshal.cpp
PurchaseOrderTypeMarshal.cpp
USAddressMarshal.cpp

    docs\

index.html  

    include\
      projectname\
        namespaces\

Items.h 
ItemsItem.h
PurchaseOrder.h
PurchaseOrderType.h
USAddress.h
ItemsMarshal.h
ItemsItemMarshal.h
PurchaseOrderTypeMarshal.h
USAddressMarshal.h

[poStatics.h]

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