Spring jdbc 批量JDBC操作、ORM映射

一、Spring JDBC 概述

Spring 提供了一个强有力的模板类JdbcTemplate简化JDBC操作，DataSource,JdbcTemplate都可以以Bean的方式定义在想xml配置文件，JdbcTemplate创建只需注入一个DataSource，应用程序Dao层只需要继承JdbcDaoSupport, 或者注入JdbcTemplate，便可以获取JdbcTemplate，JdbcTemplate是一个线程安全的类，多个Dao可以注入一个JdbcTemplate；

<!--         Oracle数据源           -->  
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">  
        <property name="driverClassName" value="oracle.jdbc.driver.OracleDriver"/>  
        <property name="url" value="jdbc:oracle:thin:@oracle.devcake.co.uk:1521:INTL"/>  
        <property name="username" value="sa"/>  
        <property name="password" value=""/>  
</bean>  
  
<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">  
        <property name="dataSource" ref="dataSource"/>  
 </bean>  
  
<bean id="customerDao" class="JdbcCustomerDao" >  
         <property name="dataSource" ref="dataSource"/>  
</bean>  
<!--         Oracle数据源           -->
<bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
        <property name="driverClassName" value="oracle.jdbc.driver.OracleDriver"/>
        <property name="url" value="jdbc:oracle:thin:@oracle.devcake.co.uk:1521:INTL"/>
        <property name="username" value="sa"/>
        <property name="password" value=""/>
</bean>

<bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <property name="dataSource" ref="dataSource"/>
 </bean>

<bean id="customerDao" class="JdbcCustomerDao" >
         <property name="dataSource" ref="dataSource"/>
</bean>

然后将jdbcTemplate对象注入自定义的Dao、或者继承JdbcDaoSupport，例如：

public class JdbcCustomerDao extends JdbcDaoSupport implements CustomerDao {  
}  
  
public class JdbcCustomerDao implements CustomerDao {  
  
          private JdbcTemplate jdbcTemplate  
  
         public void setJdbcTemplate()JdbcTemplate jdbcTemplate{  
               this.jdbcTemplate=jdbcTemplate  
         }  
}  
public class JdbcCustomerDao extends JdbcDaoSupport implements CustomerDao {
}

public class JdbcCustomerDao implements CustomerDao {

          private JdbcTemplate jdbcTemplate

         public void setJdbcTemplate()JdbcTemplate jdbcTemplate{
               this.jdbcTemplate=jdbcTemplate
         }
}

二、 JdbcTemplate 提供以下主要方法简化JDBC操作：
2.1、List query(String sql,Ojbect[] args,RowMapper rowMapper)

说明：常用的查询，sql待执行的sql语句，args是sql语句的参数，rowMapper负责将每一行记录转化为java对象存放在list，并最终返回，例如：

public List<Book> queryByAuthor(String author) {  
        String sql = "select * from book where author=?";  
        Collection c = getJdoTemplate().find(sql,  
                new Object[] { author },new BookRowMapper());  
        List<Book> books = new ArrayList<Book>();  
        books.addAll(c);  
        return books;  
}  
  
class BookRowMapper implements RowMapper{  
     public Object mapRow(ResultSet res, int index) throws SQLException {  
          Book book = new Book();  
          book.setId(rs.getInt("id"));  
          //省略set  
       return book；  
    }  
}  
public List<Book> queryByAuthor(String author) {
        String sql = "select * from book where author=?";
        Collection c = getJdoTemplate().find(sql,
                new Object[] { author },new BookRowMapper());
        List<Book> books = new ArrayList<Book>();
        books.addAll(c);
        return books;
}

class BookRowMapper implements RowMapper{
     public Object mapRow(ResultSet res, int index) throws SQLException {
          Book book = new Book();
          book.setId(rs.getInt("id"));
          //省略set
       return book；
    }
}

更新、删除、其他查询操作类似，举例如下，详细细节请参考spring api：

//返回值为一个长整形  
public long getAverageAge() {  
    return getJdbcTemplate().queryForLong("SELECT AVG(age) FROM employee");  
  }  
//返回一个整数  
public int getTotalNumberOfEmployees() {  
    return getJdbcTemplate().queryForInt("SELECT COUNT(0) FROM employees");  
  }  
  
//更新操作  
this.jdbcTemplate.update(  
        "insert into t_actor (first_name, surname) values (?, ?)",   
        new Object[] {"Leonor", "Watling"});  
//返回值为一个长整形
public long getAverageAge() {
    return getJdbcTemplate().queryForLong("SELECT AVG(age) FROM employee");
  }
//返回一个整数
public int getTotalNumberOfEmployees() {
    return getJdbcTemplate().queryForInt("SELECT COUNT(0) FROM employees");
  }

//更新操作
this.jdbcTemplate.update(
        "insert into t_actor (first_name, surname) values (?, ?)", 
        new Object[] {"Leonor", "Watling"});

2.2、spring 2.5新功能，另类的jdbc ORM：BeanPropertyRowMapper

上面我们检索时必须实现RowMapper，将结果集转化为java对象。Spring2.5 简化了这一操作，使得我们不必再实现RowMapper，实现此功能的俩个神奇东东便是：ParameterizedRowMapper，ParameterizedBeanPropertyRowMapper，貌似通过java反射机制实现了将resultset字段映射到java对象，但是数据表的列必须和java对象的属性对应，没有研究源码，有点类似于apache 的BeanUtil，不知为何这部分在spring开发参考手册没有，难道不是经典。

//使用ParameterizedBeanPropertyRowMapper  
@SuppressWarnings({"unchecked"})  
  public List<Customer> getAll() {  
      return getJdbcTemplate().query("select * from t_customer", ParameterizedBeanPropertyRowMapper.newInstance(Customer.class));  
  }  
  
//使用BeanPropertyRowMapper  
@SuppressWarnings({"unchecked"})  
  public List<Customer> getAll() {  
      return getJdbcTemplate().query("select * from t_customer", new BeanPropertyRowMapper(Customer.class));  
  }  
//使用ParameterizedBeanPropertyRowMapper
@SuppressWarnings({"unchecked"})
  public List<Customer> getAll() {
      return getJdbcTemplate().query("select * from t_customer", ParameterizedBeanPropertyRowMapper.newInstance(Customer.class));
  }

//使用BeanPropertyRowMapper
@SuppressWarnings({"unchecked"})
  public List<Customer> getAll() {
      return getJdbcTemplate().query("select * from t_customer", new BeanPropertyRowMapper(Customer.class));
  }

注意：ParameterizedBeanPropertyRowMapper是BeanPropertyRowMapper子类。另外表的字段名称必须和实体类的成员变量名称一致；

2.3、spring之JDBC批量操作

      jdbcTemplate.batchUpdate(final String[] sql) ，API解释：Issue multiple SQL updates on a single JDBC Statement using batching，翻译过来大致为：解决多个sql的插入、更新、删除操作在一个Statement中。性能一般。

   jdbcTemplate.batchUpdate(String sql, final BatchPreparedStatementSetter pss),类似于JDBC的PreparedStatement，性能较上着有所提高。

   我们举例说明如何使用，示例如下:

final int count = 2000;  
    final List<String> firstNames = new ArrayList<String>(count);  
    final List<String> lastNames = new ArrayList<String>(count);  
    for (int i = 0; i < count; i++) {  
      firstNames.add("First Name " + i);  
      lastNames.add("Last Name " + i);  
    }  
    jdbcTemplate.batchUpdate(  
            "insert into customer (id, first_name, last_name, last_login, comments) values (?, ?, ?, ?, ?)",  
            new BatchPreparedStatementSetter() {  
           //为prepared statement设置参数。这个方法将在整个过程中被调用的次数  
        public void setValues(PreparedStatement ps, int i) throws SQLException {  
                ps.setLong(1, i + 10);  
                ps.setString(2, firstNames.get(i));  
                ps.setString(3, lastNames.get(i));  
                ps.setNull(4, Types.TIMESTAMP);  
                ps.setNull(5, Types.CLOB);  
              }  
              //返回更新的结果集条数  
          public int getBatchSize() {  
                   return count;  
              }  
            });  
  }  
final int count = 2000;
    final List<String> firstNames = new ArrayList<String>(count);
    final List<String> lastNames = new ArrayList<String>(count);
    for (int i = 0; i < count; i++) {
      firstNames.add("First Name " + i);
      lastNames.add("Last Name " + i);
    }
    jdbcTemplate.batchUpdate(
            "insert into customer (id, first_name, last_name, last_login, comments) values (?, ?, ?, ?, ?)",
            new BatchPreparedStatementSetter() {
           //为prepared statement设置参数。这个方法将在整个过程中被调用的次数
        public void setValues(PreparedStatement ps, int i) throws SQLException {
                ps.setLong(1, i + 10);
                ps.setString(2, firstNames.get(i));
                ps.setString(3, lastNames.get(i));
                ps.setNull(4, Types.TIMESTAMP);
                ps.setNull(5, Types.CLOB);
              }
              //返回更新的结果集条数
          public int getBatchSize() {
                   return count;
          }
     });
  }

BatchSqlUpdate类是SqlUpdate 的子类，适用于插入、删除、更新批量操作，内部使用PreparedStatement，所以效率很高，批量语句达到设定的batchSize，或者手动调用flush才会执行批量操作。注意：此类是非线程安全的，必须为每个使用者创建一个实例，或者在同一个线程中使用前调用reset。

下面我们举例说明如何使用BatchSqlUpdate，来执行批量操作。示例如下：

class BatchInsert extends BatchSqlUpdate {  
  private static final String SQL = "insert into t_customer (id, first_name, last_name, last_login, "  
      + "comments) values (?, ?, ?, ?, null)";  
  
  BatchInsert(DataSource dataSource) {  
    super(dataSource, SQL);  
    declareParameter(new SqlParameter(Types.INTEGER));  
    declareParameter(new SqlParameter(Types.VARCHAR));  
    declareParameter(new SqlParameter(Types.VARCHAR));  
    declareParameter(new SqlParameter(Types.TIMESTAMP));  
  
    setBatchSize(10);  
  }
}  
class BatchInsert extends BatchSqlUpdate {
  private static final String SQL = "insert into t_customer (id, first_name, last_name, last_login, "
      + "comments) values (?, ?, ?, ?, null)";

  BatchInsert(DataSource dataSource) {
    super(dataSource, SQL);
    declareParameter(new SqlParameter(Types.INTEGER));
    declareParameter(new SqlParameter(Types.VARCHAR));
    declareParameter(new SqlParameter(Types.VARCHAR));
    declareParameter(new SqlParameter(Types.TIMESTAMP));

    setBatchSize(10);
  }
}

int count = 5000;  
    for (int i = 0; i < count; i++) {  
      batchInsert.update(new Object[] { i + 100L, "a" + i, "b" + i, null });  
    }  
int count = 5000;
    for (int i = 0; i < count; i++) {
      batchInsert.update(new Object[] { i + 100L, "a" + i, "b" + i, null });
    }

至此，spring JDBC主要的应用基本上都简单罗列一番

Spring jdbc 批量JDBC操作、ORM映射

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