1. public class ComputeQuence{ ComputeQuence(int n){//构造器初始化数组下标 this.n = n; } private int n = 0;//数组下标 private int sum(int count){ //通过递归来得到数组的值 if (-1 == count ){ return 0; } if ( -2 == count) return 1 ; return sum(count-1)+sum(count-2); } public int[] getQuene(){ int []S = new int[n];//结果数组 for (int i =0 ;i<n ; ++i){ S[i] = sum(i); System.out.println(S[i]); } return S; } public static void main(String[] args) { ComputeQuence c = new ComputeQuence(10); int []S = c.getQuene(); } }
public class dbTest extends HttpServlet { //Initialize global variables public void init(ServletConfig config) throws ServletException { super.init(config);
//获取记录集,并返回给VERTOR V public Vector getForumList() { String[] s = {"","","","",""} ;//与选取的列数相等。 Vector v = new Vector() ; this.initDatabaseDriver(); try{ String queryStr = null ; queryStr = "SELECT BBS_ID,BBS_NAME,DESCRIPTION,MANAGER_ID, CREATE_DATE FROM BBS WHERE IS_SYSTEM='0' ORDER BY CREATE_DATE DESC" ; ResultSet rSet = stment.executeQuery(queryStr) ; while (rSet.next()) { s[0] = Integer.toString(rSet.getInt("BBS_ID")) ; s[1] = rSet.getString("BBS_NAME") ; s[2] = rSet.getString("DESCRIPTION") ; s[3] = rSet.getString("MANAGER_ID") ; Timestamp createdate = rSet.getTimestamp("CREATE_DATE") ; String tmp = createdate.toString() ; s[4] = tmp.substring(0,(tmp.length()-2)) ; v.addElement(s.clone()); } rSet.close(); stment.close(); this.freeConnectionPool(); } catch(Exception e) { try { stment.close(); this.freeConnectionPool(); } catch(SQLException ee) { ee.printStackTrace(); } e.printStackTrace() ; } return v ; }
//Process the HTTP Get request public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = new PrintWriter (response.getOutputStream()); response.setContentType("text/html"); out.println(""); out.println("The servlet has received a GET. This is the reply."); out.println(""); out.println("");
// 将记录集循环输出到页面。 Vector v = new Vector() ; v = this.getForumList() ; for (int i=0; i" + ""+s[0]+"" + ""+s[1]+"" + ""+s[2]+"" + ""+s[3]+"" + ""+s[4]+""); } out.println(""); out.close(); } }
/** * @author Umesh * @version 1.0 * * Development Environment : Oracle9i JDeveloper * Name of the Application : ConnCacheBean.java * Creation/Modification History : * * Umesh 25-Nov-2001 Created * * Overview of Application : This Bean Class is used by all the JSPs * to perform database interaction. This class uses JDBC to perform any DML/DDL * operations. The key concept illustarted here is Connection Caching. * * As JSPs execute in middle tier, getting an individual database connection * everytime for every user is an expensive operation. This is true especially * when number of users involved are large in numbers. * * With the help of Connection Caching, the overhead of instantiating a new physical * database connection can be easily overcome. * * This bean is implemented as a SingleTon Class meaning that there can be only * one instance of this bean per JVM. In the constructor of the bean, Connection * Cache is initialized and * **/ package oracle.otnsamples.oracle9ijdbc.conncachesample;
// Connection Cache Variable private OracleConnectionCacheImpl m_ocacheimpl = null; // Data Source Variable private OracleConnectionPoolDataSource m_cpds = null; // Variable pointing to this instance private static ConnCacheBean m_thisInstance = null;
/** * Private Constructor : This approach makes it easy to implement this class as * SingleTon Class. * * This method initializes Cache if not already initialized. **/ private ConnCacheBean() throws Exception { if (m_ocacheimpl == null) initializeConnectionCache(); }
/** * Method which returns a single instance of this bean. **/ public static ConnCacheBean getInstance() throws Exception { if ( m_thisInstance == null ) { m_thisInstance = new ConnCacheBean(); } return m_thisInstance; }
2。大家能给我介绍一下,连接池吗。以及做连接池所需要的配置,急用,谢谢大家 楼上的说的就行了,如果想在web application以外用就得用apache的DBCP包了,用法很简单用: BasicDataSource bds= new BasicDataSource(); 然后设置一下url,usr,pwd, size等就行了
{
public static void main(String[] args)
{
int n0=1,n1=1,n2;
System.out.print(n0+" "+n1+" ");
for(int i=0;i<10;i++)
{
n2=n1+n0;
System.out.print(n2+" ");
n0=n1;
n1=n2;
}
System.out.println();
}
}
在连接池初始化时(或在构造函数中),生成初始个数(自定义)的数据库连接;
客户端取得连接;{当连接不够时,自动新生成指定个数的数据库连接,并将连接放入池中}
在客户端使用完连接后,主动调用返还连接的方法将用过的连接归还到连接池中.设置与此连接有关的一系列的标志,使其为初始状态.连接池的使用可节省大量的时间(频繁地生成和释放数据库连接的时间),以提高系统系统.
一、Tomcat简介
Tomcat是Apache Jakarta的子项目之一,是Sun公司推荐的JSP、Servlet容器。作为一款优秀的应用服务器,Tomcat提供了数据库连接池、SSL、Proxy等许多通用组件功能,其中连接池是4.0以上版本的新增功能,应用非常广泛。二、Tomcat4的连接池
Tomcat4的开发可分为两个阶段,4.0.6是第一阶段最推荐的release版本,内置的数据库连接池为Tyrex 0.9.7.0,Tyrex由exolab.org开发,相关信息可以参见www. exolab.org。之后,Tomcat的开发者在4.0.x的基础上对Tomcat进行了重构,重构后的release版本推荐4.1.18,这时内置的连接池改为DBCP,DBCP也是由Jakarta Commons的一个子项目。
接下来,将分别以4.0.6和4.1.18为例介绍这两种连接池对Oracle8.1.7的配置。三、对Tomcat4.0.6的Tyrex配置为方便起见,将连接池置于ROOT下,JNDI名设为jdbc/OracleDB,数据库服务器IP为192.168.0.50,SID为oradb,操作系统Win2000,jdk1.3.1,配置步骤如下。第一步:配置server.xml在server.xml文件中找到
<!-- Tomcat Root Context --><!-- <Context path="" docBase="ROOT" debug="0"/>-->
将其改为
<!-- Tomcat Root Context --> <Context path="" docBase="ROOT" debug="0"> <Resource name="jdbc/OracleDB" auth="Container" type="javax.sql.DataSource"/> <ResourceParams name="jdbc/OracleDB"> <parameter> <name>user</name> <value>holen</value> </parameter> <parameter> <name>password</name> <value>holen</value> </parameter> <parameter> <name>driverClassName</name> <value>oracle.jdbc.driver.OracleDriver</value> </parameter> <parameter> <name>driverName</name> <value>jdbc:oracle:thin:@192.168.0.50:1521:oradb</value> </parameter> </ResourceParams> </Context>说明:将ROOT的Context从注释中移出来,并定义Resource项,如下:<Resource name="jdbc/OracleDB" auth="Container" type="javax.sql.DataSource"/>Resource项(即连接池的DataSource对象),有3个属性name、auth、type,name项是JNDI的名称定义,程序通过JNDI才能找到此对象,这里取名jdbc/OracleDB;auth项即连接池管理权属性,这里取值Container,申明为容器管理;type项即对象的类型,这里取值javax.sql.DataSource,申明为数据库连接池,Tyrex不但可以用作数据库连接池,还有许多别的功能,有兴趣的朋友可以打开Tyrex的jar包看看或访问www. exolab.org,在这里就不多说了。
在接下来的<ResourceParams>域内容里包含四个参数user、password、driverClassName、driverName,依次为数据库的用户名、密码、JDBC驱动和数据库地址。
用户名、密码是为访问数据库准备的,这里均取值holen。
driverClassName即数据库的JDBC驱动名称,如Oracle8.1.7的JDBC驱动包名叫classes.jar,一般位于Oracle安装目录下的ora81\jdbc\lib目录下,初始扩展名为ZIP,需要手工把classes.zip改名为classes.jar,并放到common/lib下。这里取值oracle.jdbc.driver.OracleDriver,此类由classes.jar提供。<parameter> <name>driverClassName</name> <value>oracle.jdbc.driver.OracleDriver</value></parameter>对于其他数据库,如MySql,其driverClassName一般为org.gjt.mm.mysql.Driver。最后一个参数即driverName,即数据库的地址(准确点说应该叫url,4.1.18就改叫url了)
<parameter> <name>driverName</name> <value>jdbc:oracle:thin:@192.168.0.50:1521:oradb</value></parameter>在这里填写里的是Oracle的访问地址,若是MySql、DB2、SqlServer或其他数据库,请填写相应的地址。第二步:将Oracle的JDBC驱动classes12.jar拷贝到Tomcat安装目录的common/lib下,其他数据库也一样,请把其相应的JDBC驱动包置于common/lib,如MySql的JDBC驱动包mm.mysql-2.0.14.jar。至此,配置完成,测试代码将在后面给出。四、对Tomcat4.1.18的DBCP配置配置方法与4.0.6稍有不同,以下是配置步骤第一步:配置server.xml
在server.xml文件中找到
<!-- Tomcat Root Context --><!-- <Context path="" docBase="ROOT" debug="0"/>-->
将其改为
<!-- Tomcat Root Context --> <Context path="" docBase="ROOT" debug="0"> <Resource name="jdbc/OracleDB" auth="Container" type="javax.sql.DataSource"/> <ResourceParams name="jdbc/OracleDB"> <parameter> <name>factory</name> <value>org.apache.commons.dbcp.BasicDataSourceFactory</value> </parameter> <parameter> <name>driverClassName</name> <value>oracle.jdbc.driver.OracleDriver</value> </parameter> <parameter> <name>url</name> <value>jdbc:oracle:thin:@192.168.0.50:1521:oradb</value> </parameter> <parameter> <name>username</name> <value>holen</value> </parameter> <parameter> <name>password</name> <value>holen</value> </parameter> <parameter> <name>maxActive</name> <value>20</value> </parameter> <parameter> <name>maxIdle</name> <value>10</value> </parameter> <parameter> <name>maxWait</name> <value>-1</value> </parameter> </ResourceParams> </Context>
说明:从配置文件可以看出,DBCP的配置与Tyrex类似,但功能更加丰富。相同就不多说,重点讲述不同的地方。factory参数:<parameter> <name>factory</name> <value>org.apache.commons.dbcp.BasicDataSourceFactory</value></parameter>即基础对象工厂,这里取值org.apache.commons.dbcp.BasicDataSourceFactory,即DBCP自带的工厂,也可以用别的。
需说明一点是,虽然4.1.18里主推DBCP作连接池,但仍然可以使用Tyrex作为连接池,而且此时的Tyrex已从0.9.7.0升级到了1.0,支持JTA/JCA对象等,对象的获取仍然是通过JNDI,具体的配置方法可以参见Tomcat文档。url参数:
<parameter> <name>url</name><value>jdbc:oracle:thin:@192.168.0.50:1521:oradb</value>url是数据库访问地址,在前提已提到。接下来有三个参数,均为连接数相关,如下:
<parameter> <name>maxActive</name> <value>20</value></parameter><parameter> <name>maxIdle</name> <value>10</value></parameter><parameter><name>maxWait</name> <value>-1</value></parameter>maxActive是最大激活连接数,这里取值20个,表示同时最多有20个与数据库的连接。
maxIdle是最大空闲连接数,这里取值10个,表示即使没有连接请求时,依然可以保持10空闲的连接,而不被清除,随时处于待命状态。关于对象的状态,有兴趣的朋友可以看看EJB方面的资料。
maxWait是最大等待秒钟数,这里取值-1,表示无限等待,直到超时为止,也可以取值9000,即表示9秒后超时。
关于maxActive与maxIdle的一点建议,对于企业级应用,其两者的值一般比较接近,或者相同,关键是要分析应用的大小。第二步:配置web.xml
打开webapps/ROOT/WEB-INF下web.xml,加入如下内容: <resource-ref> <description>Oracle Datasource example</description> <res-ref-name>jdbc/OracleDB</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref>说明:此步可以省略,即不配置web.xml也可以使用连接池,但正式项目应用时还是建议加上。第三步:将Oracle的JDBC驱动classes12.jar拷贝到Tomcat安装目录的common/lib下。至此,配置完成,测试代码将在后面给出。五、测试代码下面写一个JSP文件testdb.jsp,并将testdb.jsp置于webapps/ROOT目录下,测试一下配置是否正确,此测试对以上两个版本均适合。数据库如下:Create table test(id varchar2(12),name varchar2(30))testdb.jsp内容如下:<%@ page contentType="text/html;charset=GBK"%><%@ page import= "java.sql.* "%><%@ page import= "javax.naming.* "%><% try{ Context initCtx = new InitialContext(); Context ctx = (Context) initCtx.lookup("java:comp/env"); //获取连接池对象 Object obj = (Object) ctx.lookup("jdbc/OracleDB"); //类型转换 javax.sql.DataSource ds = (javax.sql.DataSource)obj; Connection conn = ds.getConnection(); Statement stmt = conn.createStatement(); String strSql = " insert into test(id,name) values('00001','holen') "; stmt.executeUpdate(strSql); strSql = " select id,name from test "; ResultSet rs = stmt.executeQuery(strSql); if(rs.next()){ out.println(rs.getString(1)); out.println(rs.getString(2)); } }catch(Exception ex){ ex.printStackTrace(); throw new SQLException("cannot get Connection pool."); }%><hr>说明:先通过JNDI找到jdbc/OracleDB对象,这里是分两步完成的,也可以一步完成,如Object obj = (Object) ctx.lookup("java:comp/env /jdbc/OracleDB");
然后将得到的对象转换成DataSource类型,进而得到连接,得到连接后就可以进行相应的数据库操作了。
这里对数据库进行了两步操作,第一步是插入一条记录,第二步是从数据库中取出记录,并显示第一条记录的内容。打开网页,在地址栏中输入http://localhost:8080/testdb.jsp,若一切正常,将显示"00001 holen"。
ComputeQuence(int n){//构造器初始化数组下标
this.n = n;
}
private int n = 0;//数组下标
private int sum(int count){ //通过递归来得到数组的值
if (-1 == count ){
return 0;
}
if ( -2 == count)
return 1 ;
return sum(count-1)+sum(count-2);
}
public int[] getQuene(){
int []S = new int[n];//结果数组
for (int i =0 ;i<n ; ++i){
S[i] = sum(i);
System.out.println(S[i]);
}
return S;
}
public static void main(String[] args) {
ComputeQuence c = new ComputeQuence(10);
int []S = c.getQuene();
}
}
servlet连接池的例子
***************************************
import javax.servlet.* ;
import javax.servlet.http.* ;
import java.io.* ;
import java.sql.* ;
import java.util.Vector;
import oracle.jdbc.driver.*;
import java.util.Enumeration;
import java.util.Properties;
import com.unitech.connectionpool.* ;
public class dbTest extends HttpServlet {
//Initialize global variables
public void init(ServletConfig config) throws ServletException {
super.init(config);
}
// 数据库连接:Connetcion conn = null ;
Connection conn = null ;
//数据库查询内容执行:Statement stment = null ;
Statement stment = null ;
// 数据库连接池的初始化
DBConnectionManager connMgr = DBConnectionManager.getInstance();
//初始化数据库连接池,并且获取数据库连接
private void initDatabaseDriver () {
conn = connMgr.getConnection("oracle");
if (conn == null) {
System.out.println("数据库连接失败。");
return;
}
try {
stment = conn.createStatement();
}
catch (SQLException e) {
e.printStackTrace() ;
}
}
//释放数据库连接
private void freeConnectionPool() {
connMgr.freeConnection("oracle", conn) ;
}
//获取记录集,并返回给VERTOR V
public Vector getForumList() {
String[] s = {"","","","",""} ;//与选取的列数相等。
Vector v = new Vector() ;
this.initDatabaseDriver();
try{
String queryStr = null ;
queryStr = "SELECT BBS_ID,BBS_NAME,DESCRIPTION,MANAGER_ID, CREATE_DATE FROM BBS WHERE IS_SYSTEM='0' ORDER BY CREATE_DATE DESC" ;
ResultSet rSet = stment.executeQuery(queryStr) ;
while (rSet.next()) {
s[0] = Integer.toString(rSet.getInt("BBS_ID")) ;
s[1] = rSet.getString("BBS_NAME") ;
s[2] = rSet.getString("DESCRIPTION") ;
s[3] = rSet.getString("MANAGER_ID") ;
Timestamp createdate = rSet.getTimestamp("CREATE_DATE") ;
String tmp = createdate.toString() ;
s[4] = tmp.substring(0,(tmp.length()-2)) ;
v.addElement(s.clone());
}
rSet.close();
stment.close();
this.freeConnectionPool();
}
catch(Exception e) {
try {
stment.close();
this.freeConnectionPool();
}
catch(SQLException ee) {
ee.printStackTrace();
}
e.printStackTrace() ;
}
return v ;
}
//Process the HTTP Get request
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
PrintWriter out = new PrintWriter (response.getOutputStream());
response.setContentType("text/html");
out.println("");
out.println("The servlet has received a GET. This is the reply.");
out.println("");
out.println("");
// 将记录集循环输出到页面。
Vector v = new Vector() ;
v = this.getForumList() ;
for (int i=0; i"
+ ""+s[0]+""
+ ""+s[1]+""
+ ""+s[2]+""
+ ""+s[3]+""
+ ""+s[4]+"");
}
out.println("");
out.close();
}
}
---------------------------------------------------------------
如果使用应用服务器,则一般的在服务器中建立数据源和连接池,方法参看该服务器文档
程序中使用jndi进行查找数据源,然后获取连接
---------------------------------------------------------------
/**
* @author Umesh
* @version 1.0
*
* Development Environment : Oracle9i JDeveloper
* Name of the Application : ConnCacheBean.java
* Creation/Modification History :
*
* Umesh 25-Nov-2001 Created
*
* Overview of Application : This Bean Class is used by all the JSPs
* to perform database interaction. This class uses JDBC to perform any DML/DDL
* operations. The key concept illustarted here is Connection Caching.
*
* As JSPs execute in middle tier, getting an individual database connection
* everytime for every user is an expensive operation. This is true especially
* when number of users involved are large in numbers.
*
* With the help of Connection Caching, the overhead of instantiating a new physical
* database connection can be easily overcome.
*
* This bean is implemented as a SingleTon Class meaning that there can be only
* one instance of this bean per JVM. In the constructor of the bean, Connection
* Cache is initialized and
*
**/
package oracle.otnsamples.oracle9ijdbc.conncachesample;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.Statement;
import java.sql.SQLException;
import java.sql.PreparedStatement;
import oracle.jdbc.pool.OracleDataSource;
import oracle.jdbc.pool.OracleConnectionPoolDataSource;
import oracle.jdbc.pool.OracleConnectionCacheImpl;
import java.util.Hashtable;
import java.util.Vector;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.naming.NameNotFoundException;
import javax.naming.Context;
public class ConnCacheBean {
// Connection Cache Variable
private OracleConnectionCacheImpl m_ocacheimpl = null;
// Data Source Variable
private OracleConnectionPoolDataSource m_cpds = null;
// Variable pointing to this instance
private static ConnCacheBean m_thisInstance = null;
/**
* Private Constructor : This approach makes it easy to implement this class as
* SingleTon Class.
*
* This method initializes Cache if not already initialized.
**/
private ConnCacheBean() throws Exception {
if (m_ocacheimpl == null)
initializeConnectionCache();
}
/**
* Method which returns a single instance of this bean.
**/
public static ConnCacheBean getInstance() throws Exception {
if ( m_thisInstance == null ) {
m_thisInstance = new ConnCacheBean();
}
return m_thisInstance;
}
楼上的说的就行了,如果想在web application以外用就得用apache的DBCP包了,用法很简单用:
BasicDataSource bds= new BasicDataSource();
然后设置一下url,usr,pwd, size等就行了