占位符报语法错误
新增和更新方法类里面的占位符能够跑起来，但是删除和查询单个女神里面的占位符就会报语法错误，将占位符手动改为具体整型数字就可以正确运行。
以下是部分源码。
//删除功能代码块
public void delPeople (Integer id) throws SQLException {
//获取数据库连接
Connection conn = DBUtil.getConnection();
//编写sql语法规范的字符串为数据库修改数据
String sql = ""
+ " DELETE FROM test"
+ " WHERE id=?";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, id);
//通过PreparedStatement对象执行SQL语句
pstmt.execute();
}
//查询功能代码块
public People get (Integer id) throws Exception {
//获取数据库连接
Connection conn = DBUtil.getConnection();
//编写sql语法规范的字符串为数据库修改数据
String sql = ""
+ " SELECT * FROM test"
+ " WHERE id=?";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setInt(1, id);
//通过PreparedStatement对象的executeQuery方法查询数据库存储的信息
ResultSet rs = pstmt.executeQuery(sql);
People p = null;
while(rs.next()) {
p = new People();
p.setAge(rs.getInt("age"));
p.setUsername(rs.getString("username"));
p.setId(rs.getInt("id"));
p.setSex(rs.getInt("sex"));
}
return p;
}
//错误信息
Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?' at line 1
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
at com.mysql.jdbc.Util.handleNewInstance(Util.java:425)
at com.mysql.jdbc.Util.getInstance(Util.java:408)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:943)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3973)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3909)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2527)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2680)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2497)
at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2455)
at com.mysql.jdbc.StatementImpl.executeQuery(StatementImpl.java:1369)
at com.javajdbc.dao.PeopleDao.get(PeopleDao.java:103)
at com.javajdbc.peopleaction.PeopleAction.main(PeopleAction.java:35)
