spring JdbcTemplate 的若干问题-白红宇

spring JdbcTemplate 的若干问题

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发布时间：2019-05-25

本文共 32738 字，大约阅读时间需要 109 分钟。

spring的javadoc上讲getObject(String, Object[], Class) will return NULL if the result of the query is NUL 这里有0行和nullresult的区别 0行: select salary from user where 1 = 2 null result: select max(salary) from user where 1 = 2 返回就是null 0行一定抛出IncorrectResultSizeDataAccessException异常 原因如下 ResultSetMetaData rsmd = rs.getMetaData(); int nrOfColumns = rsmd.getColumnCount();这里返回ResultSet的列数 if (nrOfColumns != 1) { throw new IncorrectResultSizeDataAccessException( "Expected single column but found " + nrOfColumns, 1, nrOfColumns); } 0行,多于1行,就抛异常了 最好还是用QueryForList,返回的list的size为0,就是0行 还有oracle 10g的问题,jdbc驱动版本10.1.0.20 getObject返回一个日期类型为java.util.Date 但是这个日期只有年-月-日,没有时-分-秒,因为10g对于DATE类型的列, getObject().getClass().getName()得到 java.sql.Date System.out.println(rs.getObject("date_created") + " " + rs.getObject("date_created").getClass()); 得到 2005-10-06 class java.sql.Date 要得到全部日期,必须使用oracle.sql.TIMESTAMP 但是使用queryForObject("sql", Timestamp.class) 得到org.springframework.dao.TypeMismatchDataAccessException异常 java.sql.Timestamp] and could not be converted to required type [java.sql.Timestamp] 很是莫名其妙 只好使用java -Doracle.jdbc.V8Compatibility="true" MyApp解决

以下是对JdbcTemplate 常规用法总结:

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<li>jdbcTemplate.execute("CREATETABLEUSER(user_idinteger,namevarchar(100))");</li>

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<pre class="java" style="display: none;">jdbcTemplate.execute("CREATE TABLE USER (user_id integer, name varchar(100))");</pre>

2、如果是UPDATE或INSERT,可以用update()方法。

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<li>jdbcTemplate.update("INSERTINTOUSERVALUES('"</li>

<li>

+user.getId()+"','"

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+user.getName()+"','"

</li>

<li>

+user.getSex()+"','"

</li>

<li>

+user.getAge()+"')");

</li>

</ol>

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<pre class="java" style="display: none;">jdbcTemplate.update("INSERT INTO USER VALUES('"

+ user.getId() + "', '"

+ user.getName() + "', '"

+ user.getSex() + "', '"

+ user.getAge() + "')");

</pre>

3、带参数的更新

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<li>jdbcTemplate.update("UPDATEUSERSETname=?WHEREuser_id=?",newObject[]{name,id});</li>

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<pre class="java" style="display: none;">jdbcTemplate.update("UPDATE USER SET name = ? WHERE user_id = ?", new Object[] {name, id});</pre>

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<li>jdbcTemplate.update("INSERTINTOUSERVALUES(?,?,?,?)",newObject[]{user.getId(),user.getName(),user.getSex(),user.getAge()});</li>

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<pre class="java" style="display: none;">jdbcTemplate.update("INSERT INTO USER VALUES(?, ?, ?, ?)", new Object[] {user.getId(), user.getName(), user.getSex(), user.getAge()});

</pre>

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

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<li>intcount=jdbcTemplate.queryForInt("SELECTCOUNT(*)FROMUSER");</li>

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<pre class="java" style="display: none;">int count = jdbcTemplate.queryForInt("SELECT COUNT(*) FROM USER");</pre>

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<li>Stringname=(String)jdbcTemplate.queryForObject("SELECTnameFROMUSERWHEREuser_id=?",newObject[]{id},java.lang.String.class);</li>

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<pre class="java" style="display: none;">String name = (String) jdbcTemplate.queryForObject("SELECT name FROM USER WHERE user_id = ?", new Object[] {id}, java.lang.String.class);</pre>

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<li>Listrows=jdbcTemplate.queryForList("SELECT*FROMUSER");</li>

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<pre class="java" style="display: none;">List rows = jdbcTemplate.queryForList("SELECT * FROM USER");</pre>

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<li>Iteratorit=rows.iterator(); </li>

<li>

while(it.hasNext()){

</li>

<li>MapuserMap=(Map)it.next(); </li>

<li>

System.out.print(userMap.get("user_id")+"/t");

</li>

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System.out.print(userMap.get("name")+"/t");

</li>

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System.out.print(userMap.get("sex")+"/t");

</li>

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System.out.println(userMap.get("age")+"/t");

</li>

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<pre class="java" style="display: none;">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");

}

</pre>

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

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<li>finalStringid=user.getId(); </li>

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finalStringname=user.getName();

</li>

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finalStringsex=user.getSex()+"";

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finalintage=user.getAge();

</li>

<li>

jdbcTemplate.update("INSERTINTOUSERVALUES(?,?,?,?)",

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newPreparedStatementSetter(){

</li>

<li>

publicvoidsetValues(PreparedStatementps)throwsSQLException{

</li>

<li>

ps.setString(1,id);

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ps.setString(2,name);

</li>

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ps.setString(3,sex);

</li>

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ps.setInt(4,age);

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<pre class="java" style="display: none;">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);

}

});

</pre>

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<li>finalUseruser=newUser(); </li>

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jdbcTemplate.query("SELECT*FROMUSERWHEREuser_id=?",

</li>

<li>

</li>

<li>

</li>

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publicvoidprocessRow(ResultSetrs)throwsSQLException{

</li>

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user.setId(rs.getString("user_id"));

</li>

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user.setName(rs.getString("name"));

</li>

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user.setSex(rs.getString("sex").charAt(0));

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user.setAge(rs.getInt("age"));

</li>

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<pre class="java" style="display: none;">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"));

}

});

</pre>

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<li>classUserRowMapperimplementsRowMapper{ </li>

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publicObjectmapRow(ResultSetrs,intindex)throwsSQLException{

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Useruser=newUser();

</li>

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</li>

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</li>

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</li>

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user.setAge(rs.getInt("age"));

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returnuser;

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publicListfindAllByRowMapperResultReader(){

</li>

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Stringsql="SELECT*FROMUSER";

</li>

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returnjdbcTemplate.query(sql,newRowMapperResultReader(newUserRowMapper()));

</li>

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<pre class="java" style="display: none;">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()));

}

</pre>

在getUser(id)里面使用UserRowMapper

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<li>publicUsergetUser(finalStringid)throwsDataAccessException{ </li>

<li>

Stringsql="SELECT*FROMUSERWHEREuser_id=?";

</li>

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finalObject[]params=newObject[]{id};

</li>

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Listlist=jdbcTemplate.query(sql,params,newRowMapperResultReader(newUserRowMapper()));

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<li>

</li>

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<pre class="java" style="display: none;">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);

}

</pre>

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

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<li>publicPreparedStatementcreatePreparedStatement(Connectioncon)throwsSQLException{ </li>

<li>

</li>

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<pre class="java" style="display: none;"> public PreparedStatement createPreparedStatement(Connection con) throws SQLException {

return con.prepareStatement(sql);

}

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

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</ol>

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<pre class="java" style="display: none;"> template.update("insert into web_person values(?,?,?)",Object[]);

</pre>

或

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<li>template.update("insertintoweb_personvalues(?,?,?)",newPreparedStatementSetter(){匿名内部类只能访问外部最终局部变量 </li>

<li>

</li>

<li>

ps.setInt(index++,3);

</li>

</ol>

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<pre class="java" style="display: none;"> 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);

});

</pre>

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

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<li>publicvoidsetValues(PreparedStatementps)throwsSQLException{ </li>

<li>

ps.setInt(index++,3);

</li>

</ol>

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<pre class="java" style="display: none;"> public void setValues(PreparedStatement ps) throws SQLException {

ps.setInt(index++,3);

}

</pre>

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

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<li>publicObjectmapRow(ResultSetrs,intarg1)throwsSQLException{int表当前行数 </li>

<li>

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

</li>

<li>

Listtemplate.query("select*fromweb_personwhereid=?",Object[],RowMapper);

</li>

</ol>

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<pre class="java" style="display: none;"> 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);

</pre>

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

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<li>template.query("select*fromweb_personwhereid=?",Object[],newRowCallbackHandler(){ </li>

<li>

publicvoidprocessRow(ResultSetrs)throwsSQLException{

</li>

<li>

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

</li>

</ol>

</div>

<pre class="java" style="display: none;"> template.query("select * from web_person where id=?",Object[],new RowCallbackHandler(){

public void processRow(ResultSet rs) throws SQLException {