grailsカスタム値を手動で入力できるプライマリ・キー

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 class Part {
	String id
	String name
	static transients = ['coding']

	void setCoding(String coding)
	{
		id = coding
	}

	String getCoding(){
		return id
	}
	static mapping={
		version false
		id generator: 'assigned' //,column:'part_id'
	}
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 <g:form action="save" >
	<div class="dialog">
		<table>
			<tbody>
				<tr class="prop">
					<td valign="top" class="name">
						<label for="id"><g:message code="part.id.label" default="Id" /></label>
					</td>
					<td valign="top" class="value ${hasErrors(bean: partInstance, field: 'id', 'errors')}">
						<g:textField name="id" maxlength="20" value="${partInstance?.id}" />
					</td>
				</tr>

				<tr class="prop">
					<td valign="top" class="name">
						<label for="name"><g:message code="part.name.label" default="Name" /></label>
					</td>
					<td valign="top" class="value ${hasErrors(bean: partInstance, field: 'name', 'errors')}">
						<g:textField name="name" maxlength="40" value="${partInstance?.name}" />
					</td>
				</tr>

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    def save = {
        def partInstance = new Part(params)
	partInstance.setCoding(params.id)
        if (partInstance.save(flush: true)) {

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