Mapping SQL results to Java objects

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Mapping SQL result to container object

When a SELECT sql is executed with SQL result container class, the class is mapped with columns in the SQL result. In other words Sorm4j will use SQL result container class as the data transfer object from java.sql.ResultSet.

For converting the JDBC type to the Java class, Sorm4j refers the types of accessor (which are types of field, types of constructor parameters or types of setter parameter) in the container class. The type of accessor are expected to support returned types to be described.

Examples of SQL result container class are described at SQL result container class.

Example

In the following example, Sorm reads column id by ResultSet#getInt and column name by ResultSet#getString.

The conversion is depend on the SQL result container class not the JDBC types of the column.

If the id column has INTEGER JDBC type and the id field in corresponding container object is String class, java.sql.ResultSet#getString will be called.

code:SQL result container class example.java

public class Customer{

public int id;

public String name;

}

code:Mapping to SQL result container class example.java

// finds customers with sql query and get as List

List<Customer> list = sorm.readList(Customer.class, "select * from customer where id>?", 5);

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Mapping SQL results to standard Java objects

If a query returns a single column, Sorm can map data directly into the object (either single values or multiple values). The class of the object should be supported returned types, for example, String, Integer, Double....

code:Mapping SQL results to standard Java object Example.java

// reads customer name as String

String name = sorm.read(String.class, "select name from customer where id=?", 1);

// reads all customer id's as a list of integers

List<Integer> ids = sorm.readList(Integer.class, "select id from customer");

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Mapping SQL result to RowMap

RowMap instances can be used as SQL result container class. RowMap extends Map<String, Object>. Sorm will convert a row in SQL result to a RowMap object. The types of values are depending on JDBC type. Keys of the map are the columns name in lower case returned from the database.

code:Mapping SQL results to java.util.Map example.java

// reads a customer using a custom query and return the result as a map

RowMap customerMap = sorm.readOne(RowMap.class, "select * from customer where id=?", 10); => "{id=10, name="Alice"}"

// reads all customers and result the results as Map instances in a List

List<RowMap> customerMapList = sorm.readList(RowMap.class, "select * from customer"); => "{id=10, name="Alice"},{id=11, name="Bob"}"