java读取MySQL数据库

在String

value

=

rs.getString("name")

之前要先rs.next()一下

你用这个来判断密码错误？

if(!rs.isBeforeFirst()){

JOptionPane.showMessageDialog(frame,

"Wrong

password!")

}

isBeforeFirst()

的意思是：获取光标是否位于此

ResultSet

对象的第一行之前。

mysql里面提供了很多方法来获取表结构和表列：如下方法

获得某表所有列的信息：

String sql = select * from tname//tname为某一表名

Connection conn = ....

Statement st = conn.createStatement()

ResultSet rs = st.rs = st.executeQuery(sql)

ResultSetMetaData rsmd = rs.getMetaData()

int colcount = rsmd.getColumnCount()//取得全部列数

for(int i=0i<colcounti++){

String colname = rsmd.getColumnName(i)//取得全部列名

}

以上为某表字段具体查询，如果是查询表的信息，如在mysql服务器上那样的查询结果的话,可以用一下代码:

ResultSet.executeQuery("show tables")可以的到所有的表信息。

ResultSet.executeQuery("describe tname")可以得到表的字段信息。//tname为表名

数据库内容

  java源代码 （代码实现的是查询成绩为 的人员信息 至于其他功能的 代码中有注释） 注意 在eclipse里运行程序的时候 要工程里插入jar包 否则运行异常！ import java sql *import java io *class database_manage {  public Connection conn = null public ResultSet rs = null private String DatabaseDriver = " mysql jdbc Driver" // DataSource 数据源名称DSN  private String DatabaseConnStr = "jdbc:mysql://localhost: /people_manage?useUnicode=true&characterEncoding=utf "  + " root root" public void setDatabaseDriver(String Driver) { this DatabaseDriver = Driver }  public String getDatabaseDriver() { return (this DatabaseDriver) }  public void setDatabaseConnStr(String ConnStr) { this DatabaseConnStr = ConnStr }  public String getDatabaseConnStr() { return (this DatabaseConnStr) }  public database_manage() {// 构造函数连接数据库 try {  Class forName(DatabaseDriver)} catch (java lang ClassNotFoundException e) {  System err println("加载驱动器有错误:" + e getMessage()) System out print("执行插入有错误:" + e getMessage())// 输出到客户端 }  }  public ResultSet query(String sql) {// 查询数据库 rs = nulltry {  conn = DriverManager   getConnection(  "jdbc:mysql://localhost: /people_manage?useUnicode=true&characterEncoding=utf "  "root" "root") Statement stmt = conn createStatement() rs = stmt executeQuery(sql)} catch (SQLException ex) {  System err println("执行查询有错误:" + ex getMessage()) System out print("执行查询有错误:" + ex getMessage())// 输出到客户端 }

return rs

 }  public int update_database(String sql) {// 更新或插入数据库 int num = try {  conn = DriverManager   getConnection(  "jdbc:mysql://localhost: /people_manage?useUnicode=true&characterEncoding=utf "  "root" "root") Statement stmt = conn createStatement() num = stmt executeUpdate(sql)} catch (SQLException ex) {  System err println("执行插入有错误:" + ex getMessage()) System out print("执行插入有错误:" + ex getMessage())// 输出到客户端 } 　CloseDataBase()return num }  public void CloseDataBase() {// 关闭数据库 try {  conn close()} catch (Exception end) {  System err println("执行关闭Connection对象有错误 " + end getMessage()) System out print("执行执行关闭Connection对象有错误 有错误:" + end getMessage())// 输出到客户端 }  } } class people {  private String uid private String name private String banji private int score public people() {  }  public people(String uid String name String banji) { this uid = uidthis name = namethis banji = banji }  public people(String uid String name String banji int score) { this uid = uidthis name = namethis banji = banjithis score = score }  public String getUid() { return uid }  public void setUid(String uid) { this uid = uid }  public String getName() { return name }  public void setName(String name) { this name = name }  public String getBanji() { return banji }  public void setBanji(String banji) { this banji = banji }  public int getScore() { return score }  public void setScore(int score) { this score = score } } public class manage {  private people[] people_array // 对象数组  public void add_people(String uid String name) { 　String sql = "insert people (uid name) values ( " + uid + " " + name + " )"// sql插入语句 // String sql = "insert people (uid name) values ( uid tom )"　database_manage db_obj = new database_manage()db_obj update_database(sql) }  public void update_people(String uid String name) { 　String sql = "update people set name= " + name + " where uid= " + uid + " "database_manage db_obj = new database_manage()db_obj update_database(sql) }  public void delete_people(String uid) { 　String sql = "delete from people  where uid= " + uid + " "　database_manage db_obj = new database_manage()　db_obj update_database(sql) }  public people query_people(String uid) { database_manage db_obj = new database_manage()// String adminid=nullString uid_new name banjiuid_new = nullname = nullbanji = nullString sql_query = "select * from people where uid= " + uid + " "　try {  ResultSet rs = db_obj query(sql_query) if (rs next()) { uid_new = rs getString("uid")name = rs getString("name")banji = rs getString("banji") } } catch (Exception e) {  e getMessage()} people new_people = new people(uid_new name banji)return new_people }  public people[] query_people_byscore(int score) { database_manage db_obj = new database_manage()String uid_new name banjiuid_new = nullname = nullbanji = nullint score_new =

String sql_query = "select * from people where score=" + score// sql查询语句

try {

ResultSet rs = db_obj query(sql_query)// 查询后 返回结果集

int num =

ResultSet rs_new = rs

while (rs_new next()) {// 统计结果集中学生个数

num++

}

// System out println(num)

people_array = new people[num]

int i =

rs beforeFirst()// 返回结果集的开始

while (rs next()) {

uid_new = rs getString("uid")

name = rs getString("name")

banji = rs getString("banji")

score_new = rs getInt("score")

people_array [i] = new people(uid_new name banji score_new)

i++

}

} catch (Exception e) {

e getMessage()

}

return people_array

}

public static void main(String args[]) {

/*

* people new_people=new people()

*

* manage mr=new manage()//mr add_people(" " "小明")插入一个学生的信息

*

* new_people=mr query_people(" ")//查询uid= 的学生信息 返回对象 System out

* println(""+new_people getName()+"　 "+new_people getBanji())

* mr update_people(" " "小王")更新一个学生的信息

*

* new_people=mr query_people(" ")//更新后查询

*

* System out println(""+new_people getName()+"　 "+new_people getBanji(

* ))

*/

manage mr = new manage()

// mr delete_people(" ")删除uid= 的学生信息

people[] people_array// 声明对象数组

people_array = mr query_people_byscore( )// 返回成绩为一百的学生类数组 后输出

int num =

num = people_array length

for (int i = i <numi++) {

System out println(people_array[i] getUid() + " "

+ people_array[i] getName() + "　 "

+ people_array[i] getBanji() + "　 "

+ people_array[i] getScore())

}

}

}

lishixinzhi/Article/program/Java/JSP/201311/20030

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