When we were working on a recent Magnolia project here at Orange11, I introduced Magnolia and Blossom to a colleague of mine. Since Blossom enables the use of \u00a0Spring MVC, this enables developers to work on Magnolia integration features, without having to know the entire CMS by heart.<\/p>\n
One of the first things my colleague did, was addressing content node properties directly in the signature of the controller method. As the words left my mouth, we both realized that this would be a nice add-on for use in Blossom MVC controllers.<\/p>\n So this is why we introduced the method parameter annotation: @NodeData<\/em>. An example of the use of this annotation:<\/p>\n The method signature above would lead in the resolving of the following parameter values out of the current content node:<\/p>\n This is a very standard thing to do with Spring, but the results can be really powerful and makes the controller in combination with your content very easy to use. Also the mocking of your controller will become that much easier, because you won’t need to extract any data from a Content node anymore, but just pass the value directly as a method parameter.<\/p>\n A full tutorial and zip with sourcecode after the jump. We will start off by creating the annotation for this parameter type called @NodeData<\/em>. Now lets create the argument resolver for Spring that resolves the actual value of the parameter. One<\/strong>: Create a class that implements the WebArgumentResolver interface.<\/p>\n Two<\/strong>: Here we override the resolveArgument<\/em> method. Three<\/strong>: Check the name of the nodeData to resolve, of what type the parameter is, and based on that type, call the correct method resolving the correct value. Some code was left out for clarity here.<\/p>\n Four<\/strong>: Now we need to resolve the different types of nodeData values. Below is an example implementation for resolving String and Boolean values.<\/p>\n This is only an example of how to implement an argument resolver for your nodeData values. The implementation for resolving all of the other node types is also very trivial and more of the same, so left out for clarity, but available in a download at the bottom of this page.<\/p>\n Now that everything is in place, the only thing you would need to do here, is add your custom argument resolver to Springs’\u00a0AnnotationMethodHandlerAdapter<\/a>.<\/p>\n Locate the bean with class: When this last step is complete, it’s all done, and you can start using the @NodeData annotation in your Blossom controllers!<\/p>\n If and when you do implement this, do let us know how you get on, we’re always interested to hear about your experiences.<\/p>\n
\nWhen you are used to Spring MVC, you are also used to the fact that any relevant parameters in your method signature will automatically be resolved. But unfortunately I had to inform him that we only get the parameter types that come in through the\u00a0BlossomWebArgumentResolver<\/a> out-of-the-box.
\nHere you can read a bit\u00a0more about Blossom’s argument resolver<\/a>,\u00a0as described by Tobias Mattsson, the founder and lead developer of Blossom.<\/p>\n
\nThe annotation is quite useful in combination with Blossom. The argument resolver will try and resolve all annotated parameters from the current content node out of the aggregationState.<\/p>\n\n @RequestMapping("\/myParagraph")\n public String getStuffForMyBlossomParagraph(\n ModelMap modelMap,\n @NodeData String eventCode,\n @NodeData(name="startDate") Date date,\n @NodeData(defaultValue="true") boolean active) {\n ....\n<\/pre>\n\n
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\nAs I mentioned, creating an argumentResolver is quite trivial. But the results of such an implementation can be very useful. All that is needed for this case is:<\/p>\n\n
1. The NodeData annotation<\/h2>\n
\nThe annotation will be accessible via reflection at runtime, and will apply to method parameters.
\nThe annotation will accept:<\/p>\n\n
\npackage nl.orange11.spring.web.bind.annotation\n\/**\n * Annotation that describes a node data value\n *\n * @author erik @ Orange11\n *\n *\/\n@Target(ElementType.PARAMETER)\n@Retention(RetentionPolicy.RUNTIME)\npublic @interface NodeData {\n\n \/**\n * Alias for String name()\n *\n * @return string\n *\/\n String value() default "";\n\n \/**\n * The name of the nodeData\n *\n * @return string\n *\/\n String name() default "";\n\n \/**\n * The default value\n *\n * @return string\n *\/\n String defaultValue() default "";\n\n}\n<\/pre>\n2. An argument resolver that resolves the actual nodeData values<\/h2>\n
\nThe resolver displayed below is split up into four steps \/ excerpts of code. A link to the complete source in a zip (that will save you some copy paste work) is available at the bottom of this page.<\/p>\n\npackage nl.orange11.spring.web.bind;\n\/**\n * WebArgumentResolver that resolves @NodeData annotated method\n * parameters to their actual node data values\n *\n * @author erik @ Orange11\n *\n *\/\npublic class NodeDataArgumentResolver implements WebArgumentResolver {\n ...\n<\/pre>\n
\nWe try and get our @NodeData<\/em> annotation. When the annotation is found, we will call a method for the actual resolving of it’s value.<\/p>\n\n @Override\n public Object resolveArgument(MethodParameter methodParameter,\n NativeWebRequest webRequest) throws Exception {\n NodeData nodeDataAnnotation = methodParameter\n .getParameterAnnotation(NodeData.class);\n if (nodeDataAnnotation != null) {\n return resolveNodeDataValue(methodParameter, nodeDataAnnotation);\n }\n return UNRESOLVED;\n }\n<\/pre>\n\n private Object resolveNodeDataValue(MethodParameter methodParameter,\n NodeData nodeDataAnnotation) {\n \/\/ set the nodeDataName to the name of the parameter\n \/\/ or when not empty to the value or name of the annotation\n String nodeDataName = methodParameter.getParameterName();\n if (nodeDataAnnotation.value() != null\n && !nodeDataAnnotation.value().isEmpty()) {\n nodeDataName = nodeDataAnnotation.value();\n } else if (nodeDataAnnotation.name() != null\n && !nodeDataAnnotation.name().isEmpty()) {\n nodeDataName = nodeDataAnnotation.name();\n }\n\n \/\/ get the default value.\n String defaultValue = nodeDataAnnotation.defaultValue();\n\n \/\/ get the current content node out of the aggregationState\n Content currentContent = MgnlContext.getAggregationState()\n .getCurrentContent();\n\n \/\/ handle the different parameter types:\n Class parameterType = methodParameter.getParameterType();\n if (parameterType.equals(String.class)) {\n return resolveString(defaultValue, currentContent, nodeDataName);\n\n } else if (parameterType.equals(Boolean.class)\n || parameterType.equals(boolean.class)) {\n return resolveBoolean(defaultValue, currentContent, nodeDataName);\n\n } else if (\n ...\n return null;\n }\n<\/pre>\n\n private String resolveString(String defaultValue, Content currentContent,\n String nodeDataName) {\n \/\/ In case of a string: when empty default to null\n if (defaultValue != null && defaultValue.isEmpty()) {\n defaultValue = null;\n }\n return NodeDataUtil.getString(currentContent, nodeDataName,\n defaultValue);\n }\n\n private Boolean resolveBoolean(String defaultValue, Content currentContent,\n String nodeDataName) {\n \/\/ In case of a boolean: when empty default to false\n if ((defaultValue != null && defaultValue.isEmpty())\n || defaultValue == null) {\n defaultValue = Boolean.FALSE.toString();\n }\n return NodeDataUtil.getBoolean(currentContent, nodeDataName,\n Boolean.valueOf(defaultValue));\n }\n ...\n<\/pre>\n3. Register the argument resolver in your spring context<\/h2>\n
\norg.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter<\/em>
\nin your blossom context xml, and add your custom argument resolver bean to the list already containing Blossoms’ BlossomWebArgumentResolver<\/a>\u00a0like the example snippet below:<\/p>\n\n <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">\n <property name="customArgumentResolvers">\n <list>\n <bean class="info.magnolia.module.blossom.web.BlossomWebArgumentResolver" \/>\n <bean class="nl.orange11.spring.web.bind.NodeDataArgumentResolver" \/>\n <\/list>\n <\/property>\n <\/bean>\n<\/pre>\n
All done!<\/h2>\n