Do you want to custom a component in ESB?
First, find a demo component in your <Taklend Installation dir\plugins\org.talend.designer.camel.components.localprovider_5.2.1.r95165\components>.
Second, copy any existed component, and rename it.
Third, there are five types file. You can design your custom component according to the file.
Fourth, you can open .javajet file to code.
Hope it will help you!