在使用JDBC連接數(shù)據(jù)庫的時，我們會采用executeQuery(String sql)獲得一個結(jié)果集。當數(shù)據(jù)庫結(jié)構(gòu)變化或者獲得其他數(shù)據(jù)庫表結(jié)果集的時候我們需要將ResultSet結(jié)果集根據(jù)不同的數(shù)據(jù)結(jié)構(gòu)重新遍歷。
如何才能建立一個與數(shù)據(jù)庫結(jié)構(gòu)無關(guān)的JDBC連接呢？我們可以通過使用ResultSetMetaData()方法獲得表結(jié)構(gòu)。然后使用Object[]數(shù)組遍歷結(jié)果集。當我們要取得相應(yīng)的結(jié)果時，我們可以使用Iterator迭代器。只要遍歷迭代器就可以取出結(jié)果。
下面是我寫的一個方法：
1import java.math.BigDecimal;
2import java.sql.Connection;
3import java.sql.DriverManager;
4import java.sql.ResultSet;
5import java.sql.ResultSetMetaData;
6import java.sql.SQLException;
7import java.sql.Statement;
8import java.util.ArrayList;
9import java.util.Iterator;
10import java.util.List;
11
12public class newJdbc {
13 private String url = "jdbc:oracle:thin:@localhost:
14
15 private String dbUserName = "scott";
16
17 private String dbUserPassword = "tiger";
18
19 private Connection conn = null;
20
21 private Statement stmt = null;
22
23 private ResultSet rs = null;
24
25 public newJdbc() {
26 try {
27 Class.forName("oracle.jdbc.driver.OracleDriver");
28 } catch (ClassNotFoundException e) {
29 e.printStackTrace();
30 }
31 }
32
33 public Connection getConnection() {
34 try {
35 conn = DriverManager.getConnection(url, dbUserName, dbUserPassword);
36 } catch (SQLException e) {
37 e.printStackTrace();
38 }
39 return conn;
40 }
41
42 public void close(ResultSet rs, Statement stmt, Connection conn) {
43 if (rs != null) {
44 try {
45 rs.close();
46 } catch (SQLException e) {
47 e.printStackTrace();
48 }
49 }
50 if (stmt != null) {
51 try {
52 stmt.close();
53 } catch (SQLException e) {
54 e.printStackTrace();
55 }
56 }
57 if (conn != null) {
58 try {
59 conn.close();
60 } catch (SQLException e) {
61 e.printStackTrace();
62 }
63 }
64 }
65
66 public List query(String sql) {
67 List list = new ArrayList();
68
69 conn = this.getConnection();
70 try {
71 stmt = conn.createStatement();
72 rs = stmt.executeQuery(sql);
73 //獲取數(shù)據(jù)庫表結(jié)構(gòu)
74 ResultSetMetaData rsm = rs.getMetaData();
75 //取得數(shù)據(jù)庫的列數(shù)
76 int col = rsm.getColumnCount();
77 //生成col長度的Object數(shù)組
78 Object[] obj = new Object[col];
79 //遍歷結(jié)果集，將結(jié)果存入Object數(shù)組
80 while (rs.next()) {
81 for (int i = 0; i < col; i++) {
82 obj[i] = rs.getObject(i + 1);
83 }
84 list.add(obj);
85 }
86 } catch (SQLException e) {
87 e.printStackTrace();
88 } finally {
89 this.close(rs, stmt, conn);
90 }
91 return list;
92 }
93
94 public void update(String sql) {
95 try {
96 conn = this.getConnection();
97 stmt = conn.createStatement();
98 stmt.executeUpdate(sql);
99 } catch (SQLException e) {
100 e.printStackTrace();
101 }
102 }
103
104 public static void main(String args[]) {
105 newJdbc nj = new newJdbc();
106 String sql = "select * from users";
107 List list = nj.query(sql);
108 //返回list的迭代器
109 Iterator it = list.iterator();
110 //遍歷迭代器，取出結(jié)果 1z0-147
111 while (it.hasNext()) {
112 Object[] o = (Object[]) it.next();
113 int id = ((BigDecimal) o[0]).intValue();
114 System.out.println(id);
115 }
116
117 }
118}