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POHow to inject a service within abstract class using generics
 

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  1. POHow to inject a service within abstract class using generics
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    <p>I am attempting to create a generic abstract service class that provides common crud operations to my service layer by bringing together Service layer Objects (DTO?), Data layer Entities and their corresponding DAOs.</p> <p>The DAO layer is standard-issue abstraction where my DAOs extend an AbstractJpaImpl:</p> <pre><code>@Repository public abstract class AbstractJpaBaseDaoImpl&lt;K extends Serializable, E&gt; implements BaseDao&lt;K, E&gt; { //Dao implementation } </code></pre> <p>The DAOs extend this class and implement their respective dao interface that extends BaseDao.</p> <p>I wish to create something similar in my service layer, but how would i inject the dao itself?</p> <pre><code>public abstract class AbstractBaseCrudServiceImpl&lt;K extends Serializable, B extends AbstractBaseCrudBean, P, D extends AbstractJpaBaseDaoImpl&lt;K,P&gt;&gt; implements BaseCrudService&lt;K, B&gt; { protected Class&lt;B&gt; businessObject; protected Class&lt;P&gt; persistObject; protected Class&lt;D&gt; dao; @SuppressWarnings("unchecked") public AbstractBaseCrudServiceImpl() { //Extract the class type by accessing this classes parameters by index &lt;0,1...&gt; so 0 is K and 1 is E. this.businessObject = (Class&lt;B&gt;) ((ParameterizedType) this.getClass().getGenericSuperclass()).getActualTypeArguments()[1]; this.persistObject = (Class&lt;P&gt;) ((ParameterizedType) this.getClass().getGenericSuperclass()).getActualTypeArguments()[2]; this.dao = (Class&lt;D&gt;) ((ParameterizedType) this.getClass().getGenericSuperclass()).getActualTypeArguments()[3]; } //stuff ... @Transactional @SuppressWarnings("unchecked") @Override public void remove(B businessObject) { logger.debug("Remove " + getBusinessObjectCanonicalName() + " id= " + businessObject.getId()); try { getDao().remove(businessObject.getId()); //DOES NOT RECOGNIZE REMOVE METHOD } catch (Exception e) { logger.error("Unable to delete " + getBusinessObjectCanonicalName() + " record id=" + businessObject.getId(), e); } } //stuff ... } </code></pre> <p>Whats the cleanest way to inject a service within this abstract using generics?</p> <p><strong>D extends AbstractJpaBaseDaoImpl</strong> aint cutting it. Is there a pattern i can follow?</p>
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    1. COIs there a need that is driving the addition of generic to your services and DAOs? This feels like a bit of overkill for the sake of "type purity". In my experience, this is usually a negative ROI.
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      1. USNathan Ryan
    2. COWith each crud functionality added, there seems to be repeat work on the service layer. Was hoping to abstract this work instead of copying and pasting. Help to clean up the code and ease future additions.
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