Processing Servlet Beans

When a JSP executes a servlet bean, the dsp:droplet cycles through its code internally several times in order to arrange the servlet bean code in a manner that’s cohesive with the expectations of open parameters.

Note: All references to dsp:droplet in this section are describing the droplet tag or the class that describes it. The term servlet bean refers to a specific kind of bean implemented by a dsp:droplet tag.

Consider how the ATG platform processes this example:

<dsp:droplet name="/atg/dynamo/droplet/ForEach">
  <dsp:param name="array" bean="/samples/Student.subjects"/>
  <dsp:oparam name="output">
    <p><dsp:valueof param="element"/>
  </dsp:oparam>
</dsp:droplet>

  1. The dsp:droplet tag is called.

  2. The dsp:droplet allows its body to be executed once. During that execution, the nested input parameter tags (in this case, just array) pass their information back to dsp:droplet , which uses it to construct a table of input parameter names (array) and values (Reading; Writing; Arithmetic). The open parameter tags are ignored during this phase.

  3. The dsp:droplet finds the servlet bean referenced by the dsp:droplet “name=" property (forEach) and calls the servlet bean’s service() method with the input parameter values collected during step #2 (Reading; Writing; Arithmetic).

  4. As the servlet bean executes, the droplet halts calls to setParameter and serviceParameter, and instead records them as a list of DropletActions. These methods are organized in a manner that’s readable by the open parameters that process them and are made available to open parameters for execution.

  5. The dsp:droplet parses through each setParameter and serviceParameter method in DropletActions :

  6. Once the dsp:droplet finishes the DropletActions list, droplet execution ends.

 
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