usage.md

Usage dbc4java

To use dbc4java within your project you need to include the following dependency within your pom.xml:

<!-- Dependencies to implement Design by Contract -->
<dependency>
    <groupId>org.uniknow.agiledev</groupId>
    <artifactId>dbc4java</artifactId>
    <version>${project.version}</version>
</dependency>

Classes for which its constraints need to be verified require to be annotated with javax.validation.constraints on fields, methods, etc are also added as annotations to the class/method.

@Named
@Validated
@Scope(BeanDefinition.SCOPE_PROTOTYPE)
public class PositiveInteger {

    @Min(0)
    private int value = 0;

    public void add(int addedValue) {
        value += addedValue;
    }

    public void subtract(int subtractedValue) {
        value -= subtractedValue;
    }

    public int toInt() {
        return value;
    }
}

In the example above we assure by the constraint @Min(0) that the integer is always positive.

To assure that the constraints are validated at every method invocation all classes need to be compiled with aspectj. For that the following snippet needs to be added to your pom.xml:

<!--
AspectJ compile time weaving. Required for Design by Contract
-->
<plugin>
    <groupId>com.nickwongdev</groupId>
    <artifactId>aspectj-maven-plugin</artifactId>
    <version>${aspectj-maven-plugin.version}</version>
    <executions>
        <execution>
            <goals>
                <goal>compile</goal>
            </goals>
        </execution>
    </executions>
    <configuration>
        <source>${maven.compiler.source}</source>
        <target>${maven.compiler.target}</target>
        <showWeaveInfo>true</showWeaveInfo>
        <complianceLevel>${maven.compiler.target}</complianceLevel>

        <encoding>${project.build.sourceEncoding}</encoding>

        <weaveDependencies>
            <weaveDependency>
                <groupId>org.uniknow.agiledev</groupId>
                <artifactId>dbc4java</artifactId>
            </weaveDependency>
        </weaveDependencies>

    </configuration>
    <!--
     Ensure aspectj tools version used by compiler is the same version used as dependency. Avoids warning
     -->
    <dependencies>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjtools</artifactId>
            <version>${aspectj.version}</version>
        </dependency>
    </dependencies>
</plugin>

NOTE: dbc4java has been tested with aspectj version 1.9.6.