java ean 128

java barcode ean 128

java gs1-128

java gs1-128

java barcode ean 128

java ean 128,

java barcode ean 128,
java gs1-128,
java ean 128,
java barcode ean 128,
java gs1-128,
java gs1-128,
java gs1 128,
java gs1 128,
java gs1 128,
java ean 128,
java ean 128,
java gs1-128,
java gs1-128,
java barcode ean 128,
java barcode ean 128,
java gs1-128,
java barcode ean 128,
java barcode ean 128,
java gs1 128,
java gs1 128,

java gs1-128,
java gs1-128,
java gs1-128,
java gs1 128,
java ean 128,
java barcode ean 128,
java barcode ean 128,
java ean 128,
java barcode ean 128,
java gs1-128,
java gs1 128,
java barcode ean 128,
java barcode ean 128,
java barcode ean 128,
java ean 128,
java ean 128,
java barcode ean 128,
java gs1-128,
java gs1 128,
java ean 128,
java ean 128,
java gs1 128,
java barcode ean 128,
java gs1 128,
java gs1 128,
java gs1-128,
java ean 128,
java gs1-128,
java ean 128,
java barcode ean 128,
java gs1 128,
java ean 128,
java gs1 128,
java ean 128,
java gs1-128,
java barcode ean 128,
java gs1-128,
java barcode ean 128,
java gs1-128,
java gs1 128,
java ean 128,
java gs1 128,
java gs1-128,
java ean 128,
java gs1 128,
java barcode ean 128,
java barcode ean 128,
java ean 128,

The first advantage you may notice with this strategy is the shared declaration of superclass (or interface) properties. No longer do you have to duplicate these mappings for all concrete classes Hibernate takes care of this. Keep in mind that the SQL schema still isn t aware of the inheritance; effectively, we ve mapped two unrelated tables to a more expressive class structure. Except for the different primary key column name, the tables look exactly alike, as shown in figure 5.1. In JPA annotations, this strategy is known as TABLE_PER_CLASS:

First, we test the noop target:

@Entity @Inheritance(strategy = InheritanceType.TABLE_PER_CLASS) public abstract class BillingDetails { @Id @GeneratedValue @Column(name = "BILLING_DETAILS_ID") private Long id = null; @Column(name = "OWNER", nullable = false) private String owner; ... }

$ ant noop Buildfile: build.xml noop:

The database identifier and its mapping have to be present in the superclass, to be shared across all subclasses and their tables. An @Entity annotation on each subclass is all that is required:

do-common: noop: [echo] no-op do-ant: noop: [echo] no-op do-index: noop: [echo] no-op do-common-test: noop: [echo] no-op do-tools: noop: [echo] no-op do-webapp: noop: [echo] no-op do-all: BUILD SUCCESSFUL

@Entity @Table(name = "CREDIT_CARD") public class CreditCard extends BillingDetails { @Column(name = "NUMBER", nullable = false) private String number; ... }

Note that TABLE_PER_CLASS is specified in the JPA standard as optional, so not all JPA implementations may support it. The actual implementation is also vendor dependent in Hibernate, it s equivalent to a <union-subclass> mapping in XML files. The same mapping looks like this in a JPA XML descriptor:

A quick glance at the project dependency graph shows that we have declared the dependencies correctly, at least to the extent that the targets are executing in a valid order. The next test is more rigorous: we completely clean build the system:

<entity-mappings> <entity class="auction.model.BillingDetails" access="FIELD"> <inheritance strategy="TABLE_PER_CLASS"/> ... </entity> <entity class="auction.model.CreditCard" access="FIELD"/>

$ ant clean all ... many lines of output omitted ... BUILD SUCCESSFUL Total time: 1 minute 36 seconds

If your superclass is concrete, then an additional table is needed to hold instances of that class. We have to emphasize again that there is still no relationship between the database tables, except for the fact that they share some similar columns. The advantages of this mapping strategy are clearer if we examine polymorphic queries. For example, a query for BillingDetails executes the following SQL statement:

The success of a clean build, including the execution of all our tests, means that the build is seemingly working. Further tests on the deployed code are needed to verify that the WAR file, when deployed, is complete and correct a different problem. What we do know is that we can now clean build our entire suite of projects in less than two minutes.

select BILLING_DETAILS_ID, OWNER, NUMBER, EXP_MONTH, EXP_YEAR, ACCOUNT, BANKNAME, SWIFT CLAZZ_ from ( select BILLING_DETAILS_ID, OWNER, NUMBER, EXP_MONTH, EXP_YEAR, null as ACCOUNT, null as BANKNAME, null as SWIFT, 1 as CLAZZ_ from CREDIT_CARD union select BILLING_DETAILS_ID, OWNER, null as NUMBER, null as EXP_MONTH, null as EXP_YEAR, ... ACCOUNT, BANKNAME, SWIFT, 2 as CLAZZ_ from BANK_ACCOUNT )

This SELECT uses a FROM-clause subquery to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 1 and 2) is inserted into the intermediate result; Hibernate reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined project over the same columns; hence, we have to pad and fill up nonexistent columns with NULL. You may ask whether this query will really perform better than two separate statements. Here we can let the database optimizer find the best execution plan to combine rows from several tables, instead of merging two result sets in memory as Hibernate s polymorphic loader engine would do.

We have just shown how to subdivide a project into a number of stand-alone child projects, each with their own build files, and one master build file to integrate them all. If there is a problem in this design, it is that we do not want to have to declare the same properties and tasks in all the different child projects. There are ways to do this, which we shall now explore.