Spring 中的JdbcTemplate使用

1.JdbcTemplate的execute()方法执行SQL DDL语句,例如：

jdbcTemplate.execute("CREATE TABLE USER (user_id integer, name varchar(100))");

使用JdbcTemplate进行查询时,可以使用queryForXXX()等方法,例如使用queryForInt()方法传回user表格中的数据数目： jdbcTemplate.quertForInt("select count(*) from user"); 也可以使用queryForObject()传回一个查询后的对象,例如传回一个String对象：

String name=(String)jdbcTemplate.queryForObject("selcet name from user where id=?",new Object[]{id},java.lang.String.class);)

单独查询某个数据并赋值给特定对象时：

    public BaseObj getBaseObj(final int ID) {
        String sql = "select * from " + DB_TABLE_NAME + " where NewsId=" + ID;
        BaseObj obj =(BaseObj) getJdbcTemplate().query(sql,new ResultSetExtractor(){
            public Object extractData(ResultSet rs) throws SQLException,DataAccessException {
                if (rs.next()) {
                    NewsObj news = new NewsObj();
                    news.setID(rs.getInt("NewsID"));
                    news.setTitle(rs.getString("NewsTitle"));
                    news.setBigClass(rs.getInt("BigClassId"));
                    news.setNewsContent(rs.getString("NewsContent"));
                    news.setNewsKey(rs.getString("NewsKey"));
                    news.setNewsAuthor(rs.getString("NewsAuthor"));
                    news.setImg(rs.getBoolean("isImg"));
                    news.setNewsFrom(rs.getString("NewsFrom"));
                    return news;
                }
                return null;
            }
        });
       return obj;

    }

上面两个例子都是传回单独一笔数据,如果要传回多笔数据,则可以使用queryForList()方法

例如：
List rows=jdbcTemplate().queryForList("select * from user where id="+id.intValue()); 传回的list中包括的是map对象,每个map对象代表查询结果中的一笔数据,每笔数据包括多个字段,要取得字段中的值,就要使用字段名作为key,
例如：
    Iterator it=rows.iterator();
    while(it.hasNext()){
        Map result=(Map)it.next();
        System.out.println(userMap.get("id"));
        System.out.println(userMap.get("name"));
        System.out.println(userMap.get("age"));
     }

在查询的同时,你可以在返回结果之前先进行一些处理,这就要实现RowCallbackHandler接口

public User find(Integer id){
    final User user=new User();
    jdbcTemplate.query("select * from user where id=?",new Object[]{id},
                                     new RowCallBackHandler(){
                                           public void proccessRow(ResultSet rs){
                                                 user.setId(new Integer(rs.getInt("id")));
                                                 uset.setName(rs.getString("name"));   
                                            }});
    return user;
}

如果一次要返回多个查询结果对象,则可以实现RowMapper接口

public class UserRowMapper implements RowMapper{
        public Object MapRow(ResultSet rsmint rowNum) throws SQLException{
                User user=new User();
                user.setId(new Integer(rs.getInt("id")));
                user.setName(rs.getString("name"));
                return user;
       }
}

使用RowMapper查询单笔数据

public User find(Integer id){
         User user=(User)jdbcTemplate.queryForObject("select * from user where id=?",new Object[]{id},new UserRowMapper());
          return user;
}

使用RowMapper查询多笔数据

class UserRowMapper implements RowMapper {
         public Object mapRow(ResultSet rs,int index) throws SQLException
         {
             User u = new User();
             u.setId(rs.getString(”ID”));
             u.setName(rs.getString(”Name”));
             u.setPassword(rs.getString(”Password”));
             return u;
         }
     }
public List select(String where)
    {
        List list;       
        String sql = "select * from admin "+where;       
        list = jdbcTemplate.query(sql,new RowMapperResultReader(new UserRowMapper()));
        return list;
    }

传回的users对象中,包括了从数据库查询出来的结果,并已经封装成user对象

JdbcTemplate语句使用:

1、使用JdbcTemplate的execute()方法执行SQL语句

代码
jdbcTemplate.execute("CREATE TABLE USER (user_id integer, name varchar(100))");

2、如果是UPDATE或INSERT,可以用update()方法。

代码
jdbcTemplate.update("INSERT INTO USER VALUES('"  
            + user.getId() + "', '"  
            + user.getName() + "', '"  
            + user.getSex() + "', '"  
            + user.getAge() + "')"); 

3、带参数的更新


代码
jdbcTemplate.update("UPDATE USER SET name = ? WHERE user_id = ?", new Object[] {name, id});


代码
jdbcTemplate.update("INSERT INTO USER VALUES(?, ?, ?, ?)", new Object[] {user.getId(), user.getName(), user.getSex(), user.getAge()}); 

4、使用JdbcTemplate进行查询时,使用queryForXXX()等方法


代码
int count = jdbcTemplate.queryForInt("SELECT COUNT(*) FROM USER");


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");


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");   
} 

JdbcTemplate将我们使用的JDBC的流程封装起来,包括了异常的捕捉、SQL的执行、查询结果的转换等等。spring大量使用Template Method模式来封装固定流程的动作,XXXTemplate等类别都是基于这种方式的实现。
除了大量使用Template Method来封装一些底层的操作细节,spring也大量使用callback方式类回调相关类别的方法以提供JDBC相关类别的功能,使传统的JDBC的使用者也能清楚了解spring所提供的相关封装类别方法的使用。

JDBC的PreparedStatement


代码
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);   
                             ps.setString(2, name);             
                             ps.setString(3, sex);   
                             ps.setInt(4, age);   
                         }   
                     });  


代码
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 {   
                            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
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;   
    }   
}   
  
public List findAllByRowMapperResultReader() {   
    String sql = "SELECT * FROM USER";   
    return jdbcTemplate.query(sql, new RowMapperResultReader(new UserRowMapper()));   
}  

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);   
} 

网上收集
org.springframework.jdbc.core.PreparedStatementCreator 返回预编译SQL 不能于Object[]一起用


代码
public PreparedStatement createPreparedStatement(Connection con) throws SQLException {   
return con.prepareStatement(sql);   
} 

1.增删改
org.springframework.jdbc.core.JdbcTemplate 类(必须指定数据源dataSource)


代码
template.update("insert into web_person values(?,?,?)",Object[]); 

或


代码
template.update("insert into web_person values(?,?,?)",new PreparedStatementSetter(){ 匿名内部类 只能访问外部最终局部变量   
  
public void setValues(PreparedStatement ps) throws SQLException {   
ps.setInt(index++,3);   
}); 

org.springframework.jdbc.core.PreparedStatementSetter 接口 处理预编译SQL


代码
public void setValues(PreparedStatement ps) throws SQLException {   
ps.setInt(index++,3);   
} 

2.查询JdbcTemplate.query(String,[Object[]/PreparedStatementSetter],RowMapper/RowCallbackHandler)
org.springframework.jdbc.core.RowMapper 记录映射接口 处理结果集


代码
public Object mapRow(ResultSet rs, int arg1) throws SQLException {   int表当前行数   
person.setId(rs.getInt("id"));   
}   
List template.query("select * from web_person where id=?",Object[],RowMapper); 

org.springframework.jdbc.core.RowCallbackHandler 记录回调管理器接口 处理结果集


代码
template.query("select * from web_person where id=?",Object[],new RowCallbackHandler(){   
public void processRow(ResultSet rs) throws SQLException {   
person.setId(rs.getInt("id"));   
});