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POWhy shouldn't I use immutable POJOs instead of JavaBeans?
 

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  1. POWhy shouldn't I use immutable POJOs instead of JavaBeans?
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    <p>I have implemented a few Java applications now, only desktop applications so far. I prefer to use immutable objects for passing the data around in the application instead of using objects with mutators (setters <em>and getters</em>), also called JavaBeans.</p> <p>But in the Java world, it seems to be much more common to use JavaBeans, and I can't understand why I should use them instead. Personally the code looks better if it only deals with immutable objects instead of mutate the state all the time. </p> <p>Immutable objects are also recommended in <strong>Item 15: Minimize mutability</strong>, <em>Effective Java 2ed</em>.</p> <p>If I have an object <code>Person</code> implemented as a <strong>JavaBean</strong> it would look like:</p> <pre><code>public class Person { private String name; private Place birthPlace; public Person() {} public setName(String name) { this.name = name; } public setBirthPlace(Place birthPlace) { this.birthPlace = birthPlace; } public String getName() { return name; } public Place getBirthPlace() { return birthPlace; } } </code></pre> <p>And the same <code>Person</code> implemented as an <strong>immutable</strong> object:</p> <pre><code>public class Person { private final String name; private final Place birthPlace; public Person(String name, Place birthPlace) { this.name = name; this.birthPlace = birthPlace; } public String getName() { return name; } public Place getBirthPlace() { return birthPlace; } } </code></pre> <p>Or closer to an <code>struct</code> in C:</p> <pre><code>public class Person { public final String name; public final Place birthPlace; public Person(String name, Place birthPlace) { this.name = name; this.birthPlace = birthPlace; } } </code></pre> <p>I could also have getters in the immutable object to hide the implementation details. But since I only use it as a <code>struct</code> I prefer to skip the "getters", and keep it simple.</p> <p>Simply, I don't understand why it's better to use JavaBeans, or if I can and should keep going with my immutable POJOs?</p> <p>Many of the Java libraries seem to have better support for JavaBeans, but maybe more support for immutable POJOs gets more popular over time?</p>
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    1. COI think you mean *Item 15: Minimize mutability*, not *Minimize immutability"
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    2. CO@matt: Thanks =) I have updated it now.
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    3. COYour immutability approach is great, saves you a lot of thread issues. +1
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      1. USwhiskeysierra
 

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