Spring--JdbcTemplate详解-2

1、由于之前JdbcTemplate的程序需要编写一堆的RowMapper的映射文件，显得有些臃肿，最好是根据pojo类和字段的名称进行自动的对应，所以SimpleJdbcTemplate支持使用Pojo中的属性进行自动赋值，语法为':'开头。

Java代码

public class UserDaoSpringImpl implements UserDao {
private SimpleJdbcTemplate simpleJdbcTemplate = new SimpleJdbcTemplate(
JdbcUtils.getDataSource());
public void addUser(User user) {
String sql = "insert into user (name, money, birthday) values (:name, :money, :birthday)" ;
SqlParameterSource param = new BeanPropertySqlParameterSource(user);
KeyHolder keyHolder = new GeneratedKeyHolder();
this .simpleJdbcTemplate.getNamedParameterJdbcOperations().update(sql,
param, keyHolder);
user.setId(keyHolder.getKey().intValue());
}
public void delete(User user) {
String sql = "delete from user where id=?" ;
this .simpleJdbcTemplate.update(sql, user.getId());
}
public User findUser(String loginName, String password) {
String sql = "select id, name, money, birthday from user where name=?" ;
return this .simpleJdbcTemplate.queryForObject(sql,
ParameterizedBeanPropertyRowMapper.newInstance(User.class ),
loginName);
}
public User getUser( int userId) {
String sql = "select id, name, money, birthday from user where id=?" ;
return this .simpleJdbcTemplate.queryForObject(sql,
ParameterizedBeanPropertyRowMapper.newInstance(User.class ),
userId);
}
public void update(User user) {
String sql = "update user set name=?, birthday=?, money=? where id=? " ;
this .simpleJdbcTemplate.update(sql, user.getName(), user.getBirthday(),
user.getMoney(), user.getId());
sql = "update user set name=:name, birthday=:birthday, money=:money where id=:id " ;
this .simpleJdbcTemplate.update(sql, new BeanPropertySqlParameterSource(
user));
}
}

其中使用的JdbcUtils获取数据源的代码如下：

Java代码

public final class JdbcUtils {
private static String url = "jdbc:mysql://localhost:3306/jdbc" ;
private static String user = "root" ;
private static String password = "" ;
private static DataSource myDataSource = null ;
private JdbcUtils() {
}
static {
try {
Class.forName("com.mysql.jdbc.Driver" );
// myDataSource = new MyDataSource2();
Properties prop = new Properties();
// prop.setProperty("driverClassName", "com.mysql.jdbc.Driver");
// prop.setProperty("user", "user");
InputStream is = JdbcUtils.class .getClassLoader()
.getResourceAsStream("dbcpconfig.properties" );
prop.load(is);
myDataSource = BasicDataSourceFactory.createDataSource(prop);
} catch (Exception e) {
throw new ExceptionInInitializerError(e);
}
}
public static DataSource getDataSource() {
return myDataSource;
}
public static Connection getConnection() throws SQLException {
// return DriverManager.getConnection(url, user, password);
return myDataSource.getConnection();
}
public static void free(ResultSet rs, Statement st, Connection conn) {
try {
if (rs != null )
rs.close();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (st != null )
st.close();
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (conn != null )
try {
conn.close();
// myDataSource.free(conn);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
}

2、完成相同映射的类还包括：NamedParameterJdbcTemplate，它将之前的占位符‘？’进行了取名，方便程序的阅读。不过这样的SQL不能再数据库中直接执行，需要有Spring进行转换。

Java代码

public class NamedJdbcTemplate {
static NamedParameterJdbcTemplate named = new NamedParameterJdbcTemplate(
JdbcUtils.getDataSource());
/**
* @param args
*/
public static void main(String[] args) {
User user = new User();
user.setMoney(10 );
user.setId(2 );
System.out.println(findUser1(user));
}
static void addUser(User user) {
String sql = "insert into user(name,birthday, money) values (:name,:birthday,:money) " ;
SqlParameterSource ps = new BeanPropertySqlParameterSource(user);
KeyHolder keyHolder = new GeneratedKeyHolder();
named.update(sql, ps, keyHolder);
int id = keyHolder.getKey().intValue();
user.setId(id);
Map map = keyHolder.getKeys();
}
static User findUser(User user) {
String sql = "select id, name, money, birthday from user "
+ "where money > :m and id < :id" ;
Map params = new HashMap();
// params.put("n", user.getName());
params.put("m" , user.getMoney());
params.put("id" , user.getId());
Object u = named.queryForObject(sql, params, new BeanPropertyRowMapper(
User.class ));
return (User) u;
}
static User findUser1(User user) {
String sql = "select id, name, money, birthday from user "
+ "where money > :money and id < :id" ;
SqlParameterSource ps = new BeanPropertySqlParameterSource(user);
Object u = named.queryForObject(sql, ps, new BeanPropertyRowMapper(User. class ));
return (User) u;
}
}

【注意】

1、BeanPropertyRowMapper完成了对象到数据库字段的映射关系，可以不再使用RowMapper来一一对应起来。如果RowMapper只使用1次，则可以直接使用内部类来完成，而不再需要专门的写一个类。

2、KeyHolder，其中保存了数据库中操作的主键，取得操作的主键后，方便对进行操作的记录进行其他动作。

总之：利用反射技术，减少的了不必要的rowmapper，提高了效率

Spring--JdbcTemplate详解-2

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