使用JdbcTemplate的execute()方法执行SQL语句
execute方法总是使用 java.sql.Statement,不接受参数,而且他不返回受影响记录的计数,更适合于创建和丢弃表的语句。
jdbcTemplate.execute("CREATE TABLE USER (user_id integer, name varchar(100))");
2、增、删和改
update方法update方法返回的是受影响的记录数目的一个计数,并且如果传入参数的话,使用的是java.sql.PreparedStatement,更适合于插入,更新和删除操作
1)不带参数的更新
jdbcTemplate.update("INSERT INTO USER VALUES('" + user.getId() + "', '" + user.getName() + "', '" + user.getSex() + "', '" + user.getAge() + "')");
2)带参数的更新
jdbcTemplate.update("UPDATE USER SET name = ? WHERE user_id = ?", new Object[] {name, id}); 代码:jdbcTemplate.update("INSERT INTO USER VALUES(?, ?, ?, ?)", new Object[] {user.g etId(), user.getName(), user.getSex(), user.getAge()});
3)JDBC的PreparedStatement
------单个更新
final String id = user.getId(); final String name = user.getName(); final String sex = user.getSex() + ""; final int age = user.getAge(); jdbcTemplate.update("INSERT INTO USER VALUES(?, ?, ?, ?)", new PreparedStatementSetter() { public void setValues(PreparedStatement ps) throws SQLException { ps.setString(1, id); //需要注意: 匿名内部类 只能访问外部最终局部变量 ps.setString(2, name); ps.setString(3, sex); ps.setInt(4, age); } });
------批量更新
需要批处理,可以实现org.springframework.jdbc.core.BatchPrepared- StatementSetter接口:
package org.springframework.jdbc.core; import java.sql.PreparedStatement; import java.sql.SQLException; public interface BatchPreparedStatementSetter { void setValues(PreparedStatement ps, int i) throws SQLException; int getBatchSize(); } ... public int[] insertUsers(final List users) { String sql = "INSERT INTO user (name,age) VALUES(?,?)"; BatchPreparedStatementSetter setter = new BatchPreparedStatementSetter() { public void setValues( PreparedStatement ps, int i) throws SQLException { User user = (User) users.get(i); ps.setString(1, user.getName()); ps.setInt(2, user.getAge().intValue()); } public int getBatchSize() { return users.size(); } }; return jdbcTemplate.batchUpdate(sql, setter); }
...
如果JDBC驱动程序支持批处理,则直接使用它的功能,如果不支持, Spring则会一个一个自动处理更新以模拟批处理。
3、查询
1)使用JdbcTemplate进行查询时,使用queryForXXX()等方法
• Queries, using convenience methods
代码:
int count = jdbcTemplate.queryForInt("SELECT COUNT(*) FROMUSER");
代码:
String name = (String) jdbcTemplate.queryForObject("SELECT name FROM USER WHERE user_id = ?", new Object[] {id}, java.lang.String.class);
代码:
List rows = jdbcTemplate.queryForList("SELECT * FROM USER"); Returns an ArrayList (one entry for each row) of HashMaps (one entry for each column using the column name as the key)
代码:
List rows = jdbcTemplate.queryForList("SELECT * FROM USER"); Iterator it = rows.iterator(); while(it.hasNext()) { Map userMap = (Map) it.next(); System.out.print(userMap.get("user_id") + "\t"); System.out.print(userMap.get("name") + "\t"); System.out.print(userMap.get("sex") + "\t"); System.out.println(userMap.get("age") + "\t"); }
2)JDBC的callback方式
• Queries, using callback method
A)processRow
在查询到数据之后先作一些处理再传回。可以实现org.springframework.jdbc.core.RowCallbackHandler接口
代码:------单行查询
final User user = new User(); jdbcTemplate.query("SELECT * FROM USER WHERE user_id = ?", new Object[] {id}, new RowCallbackHandler() { public void processRow(ResultSet rs) throws SQLException { //需要注意: 匿名内部类 只能访问外部最终局部变量 user.setId(rs.getString("user_id")); user.setName(rs.getString("name")); user.setSex(rs.getString("sex").charAt(0)); user.setAge(rs.getInt("age")); } });
代码:------多行查询
final List employees = new LinkedList(); jdbc.query("select EMPNO, FIRSTNME, LASTNAME from EMPLOYEE", new RowCallbackHandler() { public void processRow(ResultSet rs) throws SQLException { Employee e = new Employee(); e.setEmpNo(rs.getString(1)); e.setFirstName(rs.getString(2)); e.setLastName(rs.getString(3)); employees.add(e); } } ); employees list will be populated with Employee objects
B) RowMapper
一次要取回很多查询结果的对象,则可以先实现org.springframe- work.jdbc.core.RowMapper接口。
代码:------将数据表中的数据影射成其对应的JAVA类的对象,mapRow回调方法会被ResultSet中的每一行调用。
class UserRowMapper implements RowMapper { public Object mapRow(ResultSet rs, int index) throws SQLException { User user = new User(); user.setId(rs.getString("user_id")); user.setName(rs.getString("name")); user.setSex(rs.getString("sex").charAt(0)); user.setAge(rs.getInt("age")); return user; } }
传回的结果已使用UserRowMapper的定义,将之封装为User对象。
//返回多行查询结果 public List findAllByRowMapperResultReader() { String sql = "SELECT * FROM USER"; return jdbcTemplate.query(sql, new RowMapperResultReader(new UserRowMapper())); } the return list will be populated with User objects //返回单行查询结果 在getUser(id)里面使用UserRowMapper 代码 public User getUser(final String id) throws DataAccessException { String sql = "SELECT * FROM USER WHERE user_id=?"; final Object[] params = new Object[] { id }; List list = jdbcTemplate.query(sql, params, new RowMapperResultReader(new UserRowMapper())); return (User) list.get(0); }