public BatchGetItemRequest withRequestItems(java.util.Map<String, KeysAndAttributes> requestItems) {
        setRequestItems(requestItems);
        return this;
    }
<p>
A map of one or more table names or table ARNs and, for each table, a map that describes one or more items to
retrieve from that table. Each table name or ARN can be used only once per <code>BatchGetItem</code> request.
</p>
<p>
Each element in the map of items to retrieve consists of the following:
</p>
<ul>
<li>
<p>
<code>ConsistentRead</code> - If <code>true</code>, a strongly consistent read is used; if <code>false</code>
(the default), an eventually consistent read is used.
</p>
</li>
<li>
<p>
<code>ExpressionAttributeNames</code> - One or more substitution tokens for attribute names in the
<code>ProjectionExpression</code> parameter. The following are some use cases for using
<code>ExpressionAttributeNames</code>:
</p>
<ul>
<li>
<p>
To access an attribute whose name conflicts with a DynamoDB reserved word.
</p>
</li>
<li>
<p>
To create a placeholder for repeating occurrences of an attribute name in an expression.
</p>
</li>
<li>
<p>
To prevent special characters in an attribute name from being misinterpreted in an expression.
</p>
</li>
</ul>
<p>
Use the <b>#</b> character in an expression to dereference an attribute name. For example, consider the following
attribute name:
</p>
<ul>
<li>
<p>
<code>Percentile</code>
</p>
</li>
</ul>
<p>
The name of this attribute conflicts with a reserved word, so it cannot be used directly in an expression. (For
the complete list of reserved words, see <a
href="https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html">Reserved Words</a> in
the <i>Amazon DynamoDB Developer Guide</i>). To work around this, you could specify the following for
<code>ExpressionAttributeNames</code>:
</p>
<ul>
<li>
<p>
<code>{"#P":"Percentile"}</code>
</p>
</li>
</ul>
<p>
You could then use this substitution in an expression, as in this example:
</p>
<ul>
<li>
<p>
<code>#P = :val</code>
</p>
</li>
</ul>
<note>
<p>
Tokens that begin with the <b>:</b> character are <i>expression attribute values</i>, which are placeholders for
the actual value at runtime.
</p>
</note>
<p>
For more information about expression attribute names, see <a href=
"https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html"
>Accessing Item Attributes</a> in the <i>Amazon DynamoDB Developer Guide</i>.
</p>
</li>
<li>
<p>
<code>Keys</code> - An array of primary key attribute values that define specific items in the table. For each
primary key, you must provide <i>all</i> of the key attributes. For example, with a simple primary key, you only
need to provide the partition key value. For a composite key, you must provide <i>both</i> the partition key
value and the sort key value.
</p>
</li>
<li>
<p>
<code>ProjectionExpression</code> - A string that identifies one or more attributes to retrieve from the table.
These attributes can include scalars, sets, or elements of a JSON document. The attributes in the expression must
be separated by commas.
</p>
<p>
If no attribute names are specified, then all attributes are returned. If any of the requested attributes are not
found, they do not appear in the result.
</p>
<p>
For more information, see <a href=
"https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html"
>Accessing Item Attributes</a> in the <i>Amazon DynamoDB Developer Guide</i>.
</p>
</li>
<li>
<p>
<code>AttributesToGet</code> - This is a legacy parameter. Use <code>ProjectionExpression</code> instead. For
more information, see <a href=
"https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/LegacyConditionalParameters.AttributesToGet.html"
>AttributesToGet</a> in the <i>Amazon DynamoDB Developer Guide</i>.
</p>
</li>
</ul>

@param requestItems
       A map of one or more table names or table ARNs and, for each table, a map that describes one or more items
       to retrieve from that table. Each table name or ARN can be used only once per <code>BatchGetItem</code>
       request.</p>
       <p>
       Each element in the map of items to retrieve consists of the following:
       </p>
       <ul>
       <li>
       <p>
       <code>ConsistentRead</code> - If <code>true</code>, a strongly consistent read is used; if
       <code>false</code> (the default), an eventually consistent read is used.
       </p>
       </li>
       <li>
       <p>
       <code>ExpressionAttributeNames</code> - One or more substitution tokens for attribute names in the
       <code>ProjectionExpression</code> parameter. The following are some use cases for using
       <code>ExpressionAttributeNames</code>:
       </p>
       <ul>
       <li>
       <p>
       To access an attribute whose name conflicts with a DynamoDB reserved word.
       </p>
       </li>
       <li>
       <p>
       To create a placeholder for repeating occurrences of an attribute name in an expression.
       </p>
       </li>
       <li>
       <p>
       To prevent special characters in an attribute name from being misinterpreted in an expression.
       </p>
       </li>
       </ul>
       <p>
       Use the <b>#</b> character in an expression to dereference an attribute name. For example, consider the
       following attribute name:
       </p>
       <ul>
       <li>
       <p>
       <code>Percentile</code>
       </p>
       </li>
       </ul>
       <p>
       The name of this attribute conflicts with a reserved word, so it cannot be used directly in an expression.
       (For the complete list of reserved words, see <a
       href="https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ReservedWords.html">Reserved
       Words</a> in the <i>Amazon DynamoDB Developer Guide</i>). To work around this, you could specify the
       following for <code>ExpressionAttributeNames</code>:
       </p>
       <ul>
       <li>
       <p>
       <code>{"#P":"Percentile"}</code>
       </p>
       </li>
       </ul>
       <p>
       You could then use this substitution in an expression, as in this example:
       </p>
       <ul>
       <li>
       <p>
       <code>#P = :val</code>
       </p>
       </li>
       </ul>
       <note>
       <p>
       Tokens that begin with the <b>:</b> character are <i>expression attribute values</i>, which are
       placeholders for the actual value at runtime.
       </p>
       </note>
       <p>
       For more information about expression attribute names, see <a href=
       "https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html"
       >Accessing Item Attributes</a> in the <i>Amazon DynamoDB Developer Guide</i>.
       </p>
       </li>
       <li>
       <p>
       <code>Keys</code> - An array of primary key attribute values that define specific items in the table. For
       each primary key, you must provide <i>all</i> of the key attributes. For example, with a simple primary
       key, you only need to provide the partition key value. For a composite key, you must provide <i>both</i>
       the partition key value and the sort key value.
       </p>
       </li>
       <li>
       <p>
       <code>ProjectionExpression</code> - A string that identifies one or more attributes to retrieve from the
       table. These attributes can include scalars, sets, or elements of a JSON document. The attributes in the
       expression must be separated by commas.
       </p>
       <p>
       If no attribute names are specified, then all attributes are returned. If any of the requested attributes
       are not found, they do not appear in the result.
       </p>
       <p>
       For more information, see <a href=
       "https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.AccessingItemAttributes.html"
       >Accessing Item Attributes</a> in the <i>Amazon DynamoDB Developer Guide</i>.
       </p>
       </li>
       <li>
       <p>
       <code>AttributesToGet</code> - This is a legacy parameter. Use <code>ProjectionExpression</code> instead.
       For more information, see <a href=
       "https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/LegacyConditionalParameters.AttributesToGet.html"
       >AttributesToGet</a> in the <i>Amazon DynamoDB Developer Guide</i>.
       </p>
       </li>
@return Returns a reference to this object so that method calls can be chained together.
aws-java-sdk-dynamodb/src/main/java/com/amazonaws/services/dynamodbv2/model/BatchGetItemRequest.java