一、

sql = "select * from  tb_user where user_name like '%'||?'%'";

pstmt.setString(1, userPartName);

二、

sql = "select * from  tb_user where user_name like ?";

pstmt.setString(1, "%" + userPartName + "%");

三、

sql = "select * from  tb_user where user_name like '%"+userPartName+"%'";