oracle pl/sql实例练习

在用JDBC进行数据库的操作的时候会在每个DAO中写有很多重复和类似的代码(建立连接,关闭连接等等),Spring的JDBC框架对这些重复的操作做了提取,形成了模板,使用Spring的JDBC框架的开发者通过提供SQL语句和在必要的时候提供callback类(用于提供更新操作的值和从返回结果集中提取返回结果),开发者就不用再去写那些重复的建立连接,关闭连接的代码了,这样不但减少了代码量,同时也避免了如忘记关闭数据库连接这类的错误.

Spring提供了如下的类来实现JDBC的基本操作和错误处理:

1,

JdbcTemplate

类:完成了资源的创建以及释放工作，从而简化了我们对JDBC的使用.JdbcTemplate将完成JDBC核心处理流程，比如建立连接,Statement的创建、SQL执行,关闭连接等.而把SQL语句的编写以及查询结果的提取工作留给我们的应用代码。它可以完成SQL查询、更新以及调用存储过程，可以对

ResultSet

进行遍历并加以提取。

2,

NamedParameterJdbcTemplate

类:在传统的SQL语句中，参数都是用

'?'

占位符来表示的.

NamedParameterJdbcTemplate可以通过冒号(:)加参数名的方式来代表

占位符(类似于PL/SQL),从而是SQL代码更可读.

3,

SimpleJdbcTemplate

类:它利用了Java 5的一些语言特性，比如Varargs和Autoboxing.(在Spring3.0中,

JdbcTemplate也支持

Varargs和Autoboxing.)

上面3个类的关系是:在最底层的调用基本上都是通过

JdbcTemplate来完成的,

NamedParameterJdbcTemplate有一个

JdbcTemplate成员变量,

SimpleJdbcTemplate有一个

NamedParameterJdbcTemplate成员变量.

4,SimpleJdbcCall类:主要用来调用承储过程和函数.

开发的常用模式(Best Practice):在访问数据库的DAO类中注入datasource,构建jdbctemplate,使用jdbctemplate完成JDBC操作.

[另外.最好是继承 JdbcDaoSupport类,这样就不用在自己的DAO类中定义JdbcTemplate成员变量和写setDataSource方法了.]

public class JDBCTestDAO {

private JdbcTemplate jdbcTemplate;

public void setDataSource(DataSource dataSource) {

this.jdbcTemplate = new JdbcTemplate(dataSource);

}

......

}

对应的配置:

<bean id="dataSource"

class="org.springframework.jdbc.datasource.DriverManagerDataSource">

<property name="driverClassName" value="oracle.jdbc.driver.OracleDriver" />

<property name="url" value="jdbc:oracle:thin:@localhost:1521:ORCL" />

<property name="username" value="user" />

<property name="password" value="pwd" />

</bean>

<bean id="JDBCTestDAO" class="com.test.spring.dao.JDBCTestDAO">

<property name="dataSource" ref="dataSource" />

</bean>

对应的数据库表为:

Create table a(id number,val varchar2(50));

1,Insert:

public void testInsert() {

this.jdbcTemplate.update(

"insert into A (ID, VAL) values (?, ?)",

"1", "val1");

}

2,update:

public void testUpdate() throws Exception {

this.jdbcTemplate.update(

"update A set val = ? where id = ?","val_bf1", "1");

}

3,delete:

public void testDelete() {

this.jdbcTemplate.update(

"delete from A");

}

4,查找单行:RowMapper的mapRow方法会被回调,用来从结果集中取值.

public void testSelectSingle(int id) {

String sql = "select id, val from A" + " where id = ?";

RowMapper<TableA> mapper = new RowMapper<TableA>() {

public TableA mapRow(ResultSet rs, int rowNum) throws SQLException {

TableA rcd = new TableA();

rcd.setId(rs.getInt("id"));

rcd.setVal(rs.getString("val"));

return rcd;

}

};

//3.0之后

JdbcTemplate也支持可变长度参数

// TableA record = (TableA) this.getJdbcTemplate().queryForObject(sql,new Object[] { id }, mapper);

TableA record = (TableA) this.getJdbcTemplate().queryForObject(sql, mapper, id);

System.out.println(record.getVal());

}

5,查找多行:RowMapper的mapRow方法会在结果集每次循环的时候被回调,用来从结果集中取值.

public void testSelectMutiple() {

String sql = "select id, val from A";

RowMapper<TableA> mapper = new RowMapper<TableA>() {

public TableA mapRow(ResultSet rs, int rowNum) throws SQLException {

TableA rcd = new TableA();

rcd.setId(rs.getInt("id"));

rcd.setVal(rs.getString("val"));

return rcd;

}

};

List<TableA> records = this.getJdbcTemplate().query(sql, mapper);

/*

* for (Iterator<TableA> itr = records.iterator(); itr.hasNext();) {

* TableA recd = itr.next(); System.out.println(recd.getVal()); }

*/

for (TableA recd : records) {

System.out.println(recd.getVal());

}

}

6,批量插入和更新:BatchPreparedStatementSetter的setValues方法会被回调用于给statement赋值.

public void testbatchInsert(final List<TableA> records) {

String sql = "insert into A values(?,?)";

int[] updateCounts = this.getJdbcTemplate().batchUpdate(sql, new BatchPreparedStatementSetter() {

public void setValues(PreparedStatement ps, int i) throws SQLException {

ps.setInt(1, records.get(i).getId());

ps.setString(2, records.get(i).getVal());

}

public int getBatchSize() {

return records.size();

}

});

}

7,利用SimpleJdbcCall调用stored procedure:

对应的数据库SP为:

CREATE OR REPLACE procedure testproc(

in_id in integer,

out_id out integer,

out_val out varchar2)

as

begin

select id,val into out_id,out_val from a where id= in_id;

end;

/

public class JDBCCallDAO extends JdbcDaoSupport {

private SimpleJdbcCall procCaller;

protected void initTemplateConfig() {

this.procCaller = new SimpleJdbcCall(this.getDataSource()).withProcedureName("TESTPROC");

}

//通过字段的metadata进行类型匹配

public void testdefaultCallSP(int id) {

SqlParameterSource in = new MapSqlParameterSource().addValue("in_id", id);

Map out = procCaller.execute(in);

System.out.println(out.get("OUT_ID"));

System.out.println((String) out.get("OUT_VAL"));

}

// 通过显示指定字段的类型

public void testExplicitCallSP(int id) {

SqlParameterSource in = new MapSqlParameterSource().addValue("in_id", id);

procCaller.withoutProcedureColumnMetaDataAccess();

procCaller.useInParameterNames("IN_ID");

procCaller.declareParameters(new SqlParameter("in_id", Types.NUMERIC), new SqlOutParameter("OUT_ID",

Types.NUMERIC), new SqlOutParameter("OUT_VAL", Types.VARCHAR));

Map out = procCaller.execute(in);

System.out.println(out.get("OUT_ID"));

System.out.println((String) out.get("OUT_VAL"));

}

......

}

8,操作LOB类型的字段:

对应的数据库表为:

create table lobtable(id number,b_lob blob,c_lob clob);

public class LobDAO {

private JdbcTemplate jdbcTemplate;

private LobHandler lobHandler = new DefaultLobHandler();

public void setDataSource(DataSource dataSource) {

this.jdbcTemplate = new JdbcTemplate(dataSource);

}

public void testInsert(int id) throws Exception {

final int v_id = id;

final byte[] blobIn = "BLOB TEST".getBytes();

final InputStream blobIs = new ByteArrayInputStream(blobIn);

final byte[] clobIn = "CLOB TEST".getBytes();

final InputStream clobIs = new ByteArrayInputStream(clobIn);

final InputStreamReader clobReader = new InputStreamReader(clobIs);

jdbcTemplate.execute("INSERT INTO lobtable (id, c_lob, b_lob) VALUES (?, ?, ?)",

new AbstractLobCreatingPreparedStatementCallback(lobHandler) {

protected void setValues(PreparedStatement ps, LobCreator lobCreator) throws SQLException {

ps.setInt(1, v_id);

lobCreator.setClobAsCharacterStream(ps, 2, clobReader, (int) clobIn.length);

lobCreator.setBlobAsBinaryStream(ps, 3, blobIs, (int) blobIn.length);

}

});

blobIs.close();

clobReader.close();

}

public void testUpdate(int id) throws Exception {

final int v_id = id;

final byte[] clobIn = "CLOB TEST UPDATE".getBytes();

final InputStream clobIs = new ByteArrayInputStream(clobIn);

final InputStreamReader clobReader = new InputStreamReader(clobIs);

jdbcTemplate.execute("UPDATE lobtable set c_lob=? where id=? ",

new AbstractLobCreatingPreparedStatementCallback(lobHandler) {

protected void setValues(PreparedStatement ps, LobCreator lobCreator) throws SQLException {

lobCreator.setClobAsCharacterStream(ps, 1, clobReader, (int) clobIn.length);

ps.setInt(2, v_id);

}

});

clobReader.close();

}

public void testReadLob() {

List<Map<String, Object>> l = jdbcTemplate.query("select id, c_lob, b_lob from lobtable",

new RowMapper<Map<String, Object>>() {

public Map<String, Object> mapRow(ResultSet rs, int i) throws SQLException {

Map<String, Object> results = new HashMap<String, Object>();

String clobText = lobHandler.getClobAsString(rs, "c_lob");

results.put("C_LOB", clobText);

byte[] blobBytes = lobHandler.getBlobAsBytes(rs, "b_lob");

results.put("B_LOB", blobBytes);

return results;

}

});

for(Map<String, Object> m:l){

System.out.println(m.get("C_LOB"));

byte[] blob = (byte[])m.get("B_LOB");

System.out.println(new String(blob));

}

}

}

默认情况下,jdbctemplate的每一个jdbc操作完成后对会提交到数据库,可以通过Spring的事务声明把这些操作组合到一个事务中而完成真正的商业逻辑.