spring替代方法

　　总结spring替代方法的使用

　　MyValueCalculator类中的computerValue方法将会被替代

public class MyValueCalculator {

    public String computeValue(String input) {
        // some real code...
    }

    // some other methods...

}

替代类实现接口MethodReplacer

/**
 * meant to be used to override the existing computeValue(String)
 * implementation in MyValueCalculator
 */
public class ReplacementComputeValue implements MethodReplacer {

    public Object reimplement(Object o, Method m, Object[] args) throws Throwable {
        // get the input value, work with it, and return a computed result
        String input = (String) args[];
        ...
        return ...;
    }
}

bean配置

<bean id="myValueCalculator" class="x.y.z.MyValueCalculator">
    <!-- arbitrary method replacement -->
    <replaced-method name="computeValue" replacer="replacementComputeValue">
        <arg-type>String</arg-type>
    </replaced-method>
</bean>

<bean id="replacementComputeValue" class="a.b.c.ReplacementComputeValue"/>

　　　　总结：这样就可以将computeValue方法交给类ReplacementComputeValue来完成。这是一种动态代理模式。由此想到了mybatis通过使用动态代理将自定义的dao接口的实现通过代理方法实现。