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3 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies). |
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38 ** $QT_END_LICENSE$ |
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40 ****************************************************************************/ |
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41 |
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42 /*! |
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43 \example xmlpatterns/schema |
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44 \title XML Schema Validation Example |
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45 |
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46 This example shows how to use QtXmlPatterns to validate XML with |
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47 a W3C XML Schema. |
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48 |
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49 \tableofcontents |
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50 |
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51 \section1 Introduction |
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52 |
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53 The example application shows different XML schema definitions and |
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54 for every definition two XML instance documents, one that is valid |
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55 according to the schema and one that is not. |
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56 The user can select the valid or invalid instance document, change |
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57 it and validate it again. |
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58 |
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59 \section2 The User Interface |
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60 |
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61 The UI for this example was created using \l{Qt Designer Manual} {Qt |
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62 Designer}: |
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63 |
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64 \image schema-example.png |
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65 |
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66 The UI consists of three parts, at the top the XML schema \l{QComboBox} {selection} |
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67 and the schema \l{QTextBrowser} {viewer}, below the XML instance \l{QComboBox} {selection} |
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68 and the instance \l{QTextEdit} {editor} and at the bottom the validation status \l{QLabel} {label} |
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69 next to the validation \l{QPushButton} {button}. |
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70 |
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71 \section2 Validating XML Instance Documents |
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72 |
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73 You can select one of the three predefined XML schemas and for each schema |
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74 an valid or invalid instance document. A click on the 'Validate' button will |
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75 validate the content of the XML instance editor against the schema from the |
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76 XML schema viewer. As you can modify the content of the instance editor, different |
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77 instances can be tested and validation error messages analysed. |
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78 |
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79 \section1 Code Walk-Through |
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80 |
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81 The example's main() function creates the standard instance of |
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82 QApplication. Then it creates an instance of the mainwindow class, shows it, |
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83 and starts the Qt event loop: |
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84 |
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85 \snippet examples/xmlpatterns/schema/main.cpp 0 |
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86 |
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87 \section2 The UI Class: MainWindow |
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88 |
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89 The example's UI is a conventional Qt GUI application inheriting |
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90 QMainWindow and the class generated by \l{Qt Designer Manual} {Qt |
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91 Designer}: |
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92 |
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93 \snippet examples/xmlpatterns/schema/mainwindow.h 0 |
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94 |
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95 The constructor fills the schema and instance \l{QComboBox} selections with the predefined |
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96 schemas and instances and connects their \l{QComboBox::currentIndexChanged()} {currentIndexChanged()} |
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97 signals to the window's \c{schemaSelected()} resp. \c{instanceSelected()} slot. |
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98 Furthermore the signal-slot connections for the validation \l{QPushButton} {button} |
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99 and the instance \l{QTextEdit} {editor} are set up. |
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100 |
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101 The call to \c{schemaSelected(0)} and \c{instanceSelected(0)} will trigger the validation |
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102 of the initial Contact Schema example. |
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103 |
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104 \snippet examples/xmlpatterns/schema/mainwindow.cpp 0 |
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105 |
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106 In the \c{schemaSelected()} slot the content of the instance \l{QComboBox} {selection} |
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107 is adapted to the selected schema and the corresponding schema is loaded from the |
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108 \l{The Qt Resource System} {resource file} and displayed in the schema \l{QTextBrowser} {viewer}. |
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109 At the end of the method a revalidation is triggered. |
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110 |
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111 \snippet examples/xmlpatterns/schema/mainwindow.cpp 1 |
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112 |
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113 In the \c{instanceSelected()} slot the selected instance is loaded from the |
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114 \l{The Qt Resource System} {resource file} and loaded into the instance \l{QTextEdit} {editor} |
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115 an the revalidation is triggered again. |
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116 |
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117 \snippet examples/xmlpatterns/schema/mainwindow.cpp 2 |
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118 |
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119 The \c{validate()} slot does the actual work in this example. |
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120 At first it stores the content of the schema \l{QTextBrowser} {viewer} and the |
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121 \l{QTextEdit} {editor} into temporary \l{QByteArray} {variables}. |
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122 Then it instanciates a \c{MessageHandler} object which inherits from |
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123 \l{QAbstractMessageHandler} {QAbstractMessageHandler} and is a convenience |
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124 class to store error messages from the XmlPatterns system. |
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125 |
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126 \snippet examples/xmlpatterns/schema/mainwindow.cpp 4 |
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127 |
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128 After the \l{QXmlSchema} {QXmlSchema} is instanciated and the message handler set |
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129 on it, the \l{QXmlSchema::load()} {load()} method is called with the schema data as argument. |
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130 If the schema is invalid or a parsing error has occured, \l{QXmlSchema::isValid()} {isValid()} |
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131 returns \c{false} and the error is flagged in \c{errorOccurred}. |
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132 If the loading was successful, a \l{QXmlSchemaValidator} {QXmlSchemaValidator} is |
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133 instanciated and the schema passed in the constructor. |
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134 A call to \l{QXmlSchemaValidator::validate()} {validate()} will validate the passed |
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135 XML instance data against the XML schema. The return value of that method signals |
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136 whether the validation was successful. |
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137 Depending on the success the status \l{QLabel} {label} is set to 'validation successful' |
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138 or the error message stored in the \c{MessageHandler} |
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139 |
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140 The rest of the code does only some fancy coloring and eyecandy. |
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141 |
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142 \snippet examples/xmlpatterns/schema/mainwindow.cpp 3 |
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143 */ |