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POSpring - set a property only if the value is not null
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  1. POSpring - set a property only if the value is not null
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    copied!<p>When using Spring, is it possible to set a property only if the value passed is not null?</p> <p>Example:</p> <pre><code>&lt;bean name="myBean" class="some.Type"&gt; &lt;property name="abc" value="${some.param}"/&gt; &lt;/bean&gt; </code></pre> <p>The behavior I'm looking for is:</p> <pre><code>some.Type myBean = new some.Type(); if (${some.param} != null) myBean.setAbc(${some.param}); </code></pre> <p>The reason I need this is since <code>abc</code> has a default value which I don't want to override with a <code>null</code>. And the Bean I am creating is not under my source control - so I cannot change its behavior. (Also, <code>abc</code> for this purpose might be a primitive, so I can't set it with a null anyway.</p> <p><strong>EDIT:</strong><br> According to the answers I think my question requires clarification.</p> <p>I have bean I need to instantiate and pass to 3rd party I use. This bean has many properties (12 currently) of various types (<code>int</code>, <code>boolean</code>, <code>String</code>, etc.)<br> Each property has a default value - I don't know what it is and would prefer not needing to know unless it becomes an issue. What I'm looking for is a generic solution that comes from Spring's abilities - currently the only solution I have is a reflection based.</p> <p><strong>Configuration</strong></p> <pre><code>&lt;bean id="myBean" class="some.TypeWrapper"&gt; &lt;property name="properties"&gt; &lt;map&gt; &lt;entry key="abc" value="${some.value}"/&gt; &lt;entry key="xyz" value="${some.other.value}"/&gt; ... &lt;/map&gt; &lt;/property&gt; &lt;/bean&gt; </code></pre> <p><strong>Code</strong></p> <pre><code>public class TypeWrapper { private Type innerBean; public TypeWrapper() { this.innerBean = new Type(); } public void setProperties(Map&lt;String,String&gt; properties) { if (properties != null) { for (Entry&lt;String, Object&gt; entry : properties.entrySet()) { String propertyName = entry.getKey(); Object propertyValue = entry.getValue(); setValue(propertyName, propertyValue); } } } private void setValue(String propertyName, Object propertyValue) { if (propertyValue != null) { Method method = getSetter(propertyName); Object value = convertToValue(propertyValue, method.getParameterTypes()[0]); method.invoke(innerBean, value); } } private Method getSetter(String propertyName) { // Assume a valid bean, add a "set" at the beginning and toUpper the 1st character. // Scan the list of methods for a method with the same name, assume it is a "valid setter" (i.e. single argument) ... } private Object convertToValue(String valueAsString, Class type) { // Check the type for all supported types and convert accordingly if (type.equals(Integer.TYPE)) { ... } else if (type.equals(Integer.TYPE)) { ... } ... } } </code></pre> <p>The real "difficulty" is in implementing <code>convertToValue</code> for all possible value types. I have done this more than once in my life - so it is not a major issue to implement it for all possible types that I need (mostly primitives and a few enums) - but I hoped a more intelligent solution existed.</p>
 

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