@Documented
@Retention(value=RUNTIME)
@Target(value=FIELD)
public @interface Expose
This annotation has no effect unless you build Gson
with a GsonBuilder and invoke
GsonBuilder.excludeFieldsWithoutExposeAnnotation()
method.
Here is an example of how this annotation is meant to be used:
public class User {
@Expose private String firstName;
@Expose(serialize = false) private String lastName;
@Expose (serialize = false, deserialize = false) private String emailAddress;
private String password;
}
</pre></p>
If you created Gson with <code>new Gson()</code>, the <code>toJson()</code> and <code>fromJson()</code>
methods will use the <code>password</code> field along-with <code>firstName</code>, <code>lastName</code>,
and <code>emailAddress</code> for serialization and deserialization. However, if you created Gson
with <code>Gson gson = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().create()</code>
then the <code>toJson()</code> and <code>fromJson()</code> methods of Gson will exclude the
<code>password</code> field. This is because the <code>password</code> field is not marked with the
<code>@Expose</code> annotation. Gson will also exclude <code>lastName</code> and <code>emailAddress</code>
from serialization since <code>serialize</code> is set to <code>false</code>. Similarly, Gson will
exclude <code>emailAddress</code> from deserialization since <code>deserialize</code> is set to false.
<p>Note that another way to achieve the same effect would have been to just mark the
<code>password</code> field as <code>transient</code>, and Gson would have excluded it even with default
settings. The <code>@Expose</code> annotation is useful in a style of programming where you want to
explicitly specify all fields that should get considered for serialization or deserialization.</div>
<dl>
<dt><span class="simpleTagLabel">Author:</span></dt>
<dd>Inderjeet Singh, Joel Leitch</dd>
</dl>
</li>
</ul>
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<h3>Optional Element Summary</h3>
<table class="memberSummary" border="0" cellpadding="3" cellspacing="0" summary="Optional Element Summary table, listing optional elements, and an explanation">
<caption><span>Optional Elements</span><span class="tabEnd"> </span></caption>
<tr>
<th class="colFirst" scope="col">Modifier and Type</th>
<th class="colLast" scope="col">Optional Element and Description</th>
</tr>
<tr class="altColor">
<td class="colFirst"><code>boolean</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../com/google/gson/annotations/Expose.html#deserialize--">deserialize</a></span></code>
<div class="block">If <code>true</code>, the field marked with this annotation is deserialized from the JSON.</div>
</td>
</tr>
<tr class="rowColor">
<td class="colFirst"><code>boolean</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../com/google/gson/annotations/Expose.html#serialize--">serialize</a></span></code>
<div class="block">If <code>true</code>, the field marked with this annotation is written out in the JSON while
serializing.</div>
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<a name="serialize--">
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<h4>serialize</h4>
<pre>public abstract boolean serialize</pre>
<div class="block">If <code>true</code>, the field marked with this annotation is written out in the JSON while
serializing. If <code>false</code>, the field marked with this annotation is skipped from the
serialized output. Defaults to <code>true</code>.</div>
<dl>
<dt><span class="simpleTagLabel">Since:</span></dt>
<dd>1.4</dd>
</dl>
<dl>
<dt>Default:</dt>
<dd>true</dd>
</dl>
</li>
</ul>
</li>
</ul>
<ul class="blockList">
<li class="blockList"><a name="deserialize--">
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</a>
<ul class="blockListLast">
<li class="blockList">
<h4>deserialize</h4>
<pre>public abstract boolean deserialize</pre>
<div class="block">If <code>true</code>, the field marked with this annotation is deserialized from the JSON.
If <code>false</code>, the field marked with this annotation is skipped during deserialization.
Defaults to <code>true</code>.</div>
<dl>
<dt><span class="simpleTagLabel">Since:</span></dt>
<dd>1.4</dd>
</dl>
<dl>
<dt>Default:</dt>
<dd>true</dd>
</dl>
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