? ?

java resultset是什么？讓我們一起來了解一下吧！

java resultset是我們?cè)谶\(yùn)用jdbc進(jìn)行對(duì)接的時(shí)候，查詢出的一個(gè)返回結(jié)果集合。Resultset的功能就是完成了存儲(chǔ)查詢結(jié)果，但是它只能讀取一次，不能做到滾動(dòng)讀取。

?

ResultSetMetaData：

我們可以應(yīng)用?ResultSet.getMetaData() 方法來得到?ResultSetMetaData。通過該信息能夠得到表的結(jié)構(gòu)，比如說列名，列的個(gè)數(shù)，列數(shù)據(jù)類型等。

一.獲取列名

ResultSetMetaData.getColumnName(m);

獲取第m位的列名

二.獲取列個(gè)數(shù)

ResultSetMetaData.getColumnCount();

獲取列的個(gè)數(shù)

三．獲得列類型

1.ResultSetMetaData.getColumnType(m);

獲取第m位的列類型，對(duì)應(yīng)java.sql.Types中的數(shù)據(jù)信息

2.ResultSetMetaData.getColumnTypeName(m);

獲取第m位的列類型名稱

實(shí)戰(zhàn)演練，具體步驟如下：

package?com.lingaolu.Utils;
?
import?java.io.FileReader;
import?java.io.IOException;
import?java.net.URL;
import?java.sql.*;
import?java.util.Properties;
?

public?class?JdbcUtils?{
????private?static?String?driver;
????private?static?String?url;
????private?static?String?userName;
????private?static?String?pw;
?
????static{
????????try?{
????????????Properties?p?=?new?Properties();
????????????ClassLoader?classLoader?=?JdbcUtils.class.getClassLoader();
????????????//?這個(gè)路徑相對(duì)于src的路徑來說
????????????URL?resource?=?classLoader.getResource("com/file/jdbc.properties");
????????????String?path?=?resource.getPath();
????????????p.load(new?FileReader(path));
????????????driver?=?p.getProperty("driver");
????????????url?=?p.getProperty("url");
????????????userName?=?p.getProperty("user");
????????????pw?=?p.getProperty("password");
????????????Class.forName(driver);
????????}?catch?(IOException?e)?{
????????????e.printStackTrace();
????????}?catch?(ClassNotFoundException?e)?{
????????????e.printStackTrace();
????????}
????}
?
????public?static?Connection?createConnection()?throws?SQLException?{
????????return?DriverManager.getConnection(url,?userName,?pw);
????}
?
????public?static?void?close(Statement?stmt,Connection?con){
????????if(null?!=?stmt){
????????????try?{
????????????????stmt.close();
????????????}?catch?(SQLException?e)?{
????????????????e.printStackTrace();
????????????}
????????}
????????if(null?!=?con){
????????????try?{
????????????????con.close();
????????????}?catch?(SQLException?e)?{
????????????????e.printStackTrace();
????????????}
????????}
????}
?
????public?static?void?close(ResultSet?set,Statement?s,Connection?con){
????????if(null?!=?set){
????????????try?{
????????????????set.close();
????????????}?catch?(SQLException?e)?{
????????????????e.printStackTrace();
????????????}
????????}
????????close(s,con);
????}
}
package?com.lingaolu.jdbcConnector;
?
import?com.lingaolu.Utils.JdbcUtils;
?
import?java.sql.*;
import?java.util.ArrayList;
import?java.util.List;
?

public?class?Demo3?{
????public?static?void?main(String[]?args)?{
????????String?sql?=?"select?*?from?account";
????????List?accounts?=?fineAccount(sql);
????????accounts.forEach(System.out::println);
????????System.out.println("----------------------------------");
????????sql?=?"select?*?from?account?where?name='張三'";
????????accounts?=?fineAccount(sql);
????????accounts.forEach(System.out::println);
????}
?
????public?static?List?fineAccount(String?sql){
????????Connection?con?=?null;
????????Statement?stmt?=?null;
????????ResultSet?resultSet?=?null;
????????List?rerurnList?=?new?ArrayList<>();
????????try?{
????????????con?=?JdbcUtils.createConnection();
????????????stmt?=?con.createStatement();
????????????resultSet?=?stmt.executeQuery(sql);
????????????Account?acc?=?null;
????????????while(resultSet.next()){
????????????????//?引號(hào)里的字段要與表里的一樣
????????????????int?id?=?resultSet.getInt("id");
????????????????String?name?=?resultSet.getString("name");
????????????????double?balance?=?resultSet.getDouble("balance");
????????????????int?age?=?resultSet.getInt("age");
?
????????????????acc?=?new?Account();
????????????????acc.setId(id);
????????????????acc.setName(name);
????????????????acc.setBalance(balance);
????????????????acc.setMyAge(age);
?
????????????????rerurnList.add(acc);
????????????}
????????}?catch?(SQLException?e)?{
????????????e.printStackTrace();
????????}finally?{
????????????JdbcUtils.close(resultSet,stmt,con);
????????}
????????return?rerurnList;
????}
}

以上就是小編今天的分享了，希望可以幫助到大家。