Schedule: Timing Topic. 15 minutes Lecture 00 minutes Practice 15 minutes Total

Transcription

1 Schedule: Timing Topic 15 minutes Lecture 00 minutes Practice 15 minutes Total

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3 Annotations are one of the newer trends in Java development. Annotations, simply put, are markers or hints to the compiler of a virtual machine that a class exhibits a certain behavior or characteristic. In essence, an annotation is a mechanism for associating metatags with program elements and allowing the compiler or the virtual machine to extract program behaviors from these annotated elements. Coherence can use annotations to specify that a class is serializable and which properties and methods should be serialized.

4 POF Serialization supports annotations to define which classes and within which methods and properties should support serialization. The underlying class, com.tangosol.io.pof.pofannotationserialer can read and act on annotations within a class to serialize and deserialize its elements. This class, along with its specific annotations provides developers with an alternative to developing against PortableObject and the PofSerializer interfaces themselves. Using these annotations, a class can be quickly and easily marked for serialization. While complex serializations will still require implementation of PortableObject and so on, simple entity classes can be marked for serialization quickly using POF annotations.

5 Two new annotations have been added to support automated generation of POF. These annotations are available to indicate a class and its properties are POF Marks the class as POF serializable. The annotation is only permitted at the class level and has no Marks a member variable or method accessor as a POF serialized attribute. Annotated methods must conform to accessor notation (get, set, is). This annotation takes two possible parameters, value and codec. Value specifies the index of the field, while codec is used to specify a concrete implementation of a class when an object returns an interface. An example of when to use a codec might be when a method return type is a Map. In such a situation, a codec would be used to instruct the system to return a specific implementation of the Map interface such as LinkedHashMap.

6 Specifying annotations requires two specific steps. First, a class must be annotated. In the example shown, the class is annotated as well as both methods and properties. Note that only some of the fields are shown in the example, however, indexes would be specified as consecutive integers. After it is annotated, the class needs to be noted in a pof-config.xml file. In the example shown, the pof-config shows the class being assigned a type-id of 1001.

7 To further simplify the process of using POF annotations, developers can auto assign index values to class fields and methods rather than hard coding values into a class. When using the auto indexing feature, a developer ignores the value attribute of the PortableProperty field. The serializer then automatically assigns indexes to properties. Note that you can still selectively use indexes in your class, with the POF serialization filling in any missing indexes. The POF Serializer class, by default, does NOT implement auto indexing. To use the auto indexing feature, enable auto indexing by using a serializer element as described in the next slide.

8 To use the auto index feature of Coherence without indexes, you must configure the serializer class to enable auto indexing. To enable this feature, you must first add a serializer element to the configuration for the class to be serialized. This element supports the class sub-element. The class element supports defining the class associated with a given feature or function. In this case, the com.tangosol.io.pof.pofannotationserializer class. This class has two constructors, the second of which supports enabling auto-indexing by setting the third parameter to true as shown above.

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