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POUsing Reflection to auto-fill in defaults in an object where possible
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  1. POUsing Reflection to auto-fill in defaults in an object where possible
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    copied!<p>Here is some code I've been twiddling with to try and lazily fill in fields in object, mostly for object factories in JUnit but it could be quite a useful method to have.</p> <pre><code> private void lazyObjectFill(Object profil) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { final Method[] list = profil.getClass().getDeclaredMethods(); for (Method m : list) { if (Modifier.isPublic(m.getModifiers()) &amp;&amp; m.getName().startsWith("set")) { final Class&lt; ?&gt;[] parameterTypes = m.getParameterTypes(); if (parameterTypes.length == 1) { final Class&lt; ?&gt; clazz = parameterTypes[0]; if (clazz == String.class) { log.info("Invoking " + m.getName() + " with [\"\"]"); m.invoke(""); } else if (clazz.isPrimitive() &amp;&amp; Defaults.defaultValue(clazz) != null) { log.info("Invoking " + m.getName() + " with [" + Defaults.defaultValue(clazz) + "]"); m.invoke(Defaults.defaultValue(clazz)); } } } } } </code></pre> <p>We get the following exception when running this code on an object.</p> <pre><code>java.lang.IllegalArgumentException: object is not an instance of declaring class at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:592) </code></pre> <p>The exception occurs when running m.invoke(""); on a string setter.</p> <hr> <p>Updated source code for the benefit of the googlers.</p> <pre><code>private void lazyObjectFill(Object obj) throws IllegalArgumentException, IllegalAccessException, InvocationTargetException { final Method[] list = obj.getClass().getDeclaredMethods(); for (Method method : list) { method.setAccessible(true); if (Modifier.isPublic(method.getModifiers()) &amp;&amp; method.getName().startsWith("set")) { final Class&lt; ?&gt;[] parameterTypes = method.getParameterTypes(); if (parameterTypes.length == 1) { final Class&lt; ?&gt; clazz = parameterTypes[0]; if (clazz == String.class) { log.info("Invoking " + method.getName() + " with [\"\"]"); method.invoke(obj, ""); } else if (clazz.isPrimitive() &amp;&amp; Defaults.defaultValue(clazz) != null) { log.info("Invoking " + method.getName() + " with [" + Defaults.defaultValue(clazz) + "]"); method.invoke(obj, Defaults.defaultValue(clazz)); } } } } } </code></pre>
 

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