1，需要修改

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中的context.xml文件：

添加：

 
 

  
  
<ResourcedriverClassName="org.postgresql.Driver"maxActive="4"maxIdle="2"maxWait="50"
  
  
auth="Container"
  
  
name="jdbc/postg"password="root"type="javax.sql.DataSource"
  
  
url="jdbc:postgresql://192.168.2.150:5432/postgres"username="postgres"/>
  
  

 
 

工具类：ConnUtil

 
 

  
  
packagecom.hw.util;
  
  

  
  
importjava.sql.Connection;
  
  
importjava.sql.DriverManager;
  
  
importjava.sql.sqlException;
  
  

  
  
importjavax.naming.Context;
  
  
importjavax.naming.InitialContext;
  
  
importjavax.naming.NamingException;
  
  
importjavax.sql.DataSource;
  
  

  
  
publicclassConnUtil
  
  
{
  
  
publicstaticConnectiongetConn()
  
  
{
  
  
Connectionconn=null;
  
  
try
  
  
{
  
  
Class.forName("org.postgresql.Driver");
  
  
Stringurl="jdbc:postgresql://192.168.2.150:5432/postgres";
  
  
try
  
  
{
  
  
conn=DriverManager.getConnection(url,"postgres","postgres");
  
  
}
  
  
catch(sqlExceptione)
  
  
{
  
  
e.printStackTrace();
  
  
}
  
  
}
  
  
catch(ClassNotFoundExceptione)
  
  
{
  
  
e.printStackTrace();
  
  
}
  
  

  
  
returnconn;
  
  
}
  
  
publicstaticConnectiongetJNDIConn(){
  
  
Contextctx=null;
  
  
try
  
  
{
  
  
ctx=newInitialContext();
  
  
}
  
  
catch(NamingExceptione1)
  
  
{
  
  
e1.printStackTrace();
  
  
}
  
  
Connectionconn=null;
  
  
DataSourceds=null;;
  
  
try
  
  
{
  
  
ds=(DataSource)ctx.lookup("java:comp/env/jdbc/postg");
  
  
}
  
  
catch(NamingExceptione)
  
  
{
  
  
e.printStackTrace();
  
  
}
  
  
try
  
  
{
  
  
conn=ds.getConnection();
  
  
}
  
  
catch(sqlExceptione)
  
  
{
  
  
e.printStackTrace();
  
  
}
  
  
returnconn;
  
  
}
  
  

  
  
}
 
 

servlet：

 
 

  
  
packagecom.hw.servlet;
  
  

  
  
importjava.io.IOException;
  
  
importjava.io.PrintWriter;
  
  
importjava.sql.Connection;
  
  
importjava.sql.ResultSet;
  
  
importjava.sql.sqlException;
  
  
importjava.sql.Statement;
  
  

  
  
importjavax.servlet.ServletException;
  
  
importjavax.servlet.http.HttpServlet;
  
  
importjavax.servlet.http.HttpServletRequest;
  
  
importjavax.servlet.http.HttpServletResponse;
  
  

  
  
importcom.hw.util.ConnUtil;
  
  

  
  
/**
  
  
*ServletimplementationclassPostgreServlet
  
  
*/
  
  
publicclassPostgreServletextendsHttpServlet{
  
  
privatestaticfinallongserialVersionUID=1L;
  
  

  
  
/**
  
  
*@seeHttpServlet#HttpServlet()
  
  
*/
  
  
publicPostgreServlet(){
  
  
super();
  
  
}
  
  

  
  
/**
  
  
*@seeHttpServlet#doGet(HttpServletRequestrequest,HttpServletResponseresponse)
  
  
*/
  
  
protectedvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)throwsServletException,IOException{
  
  
Connectionconn=ConnUtil.getJNDIConn();
  
  
Stringsql="select*fromstudent";
  
  
Statementstmt=null;
  
  
ResultSetrs=null;
  
  
PrintWriterout=response.getWriter();
  
  
try
  
  
{
  
  
stmt=conn.createStatement();
  
  
rs=stmt.executeQuery(sql);
  
  
while(rs.next()){
  
  
out.println(rs.getInt(1));
  
  
}
  
  
}
  
  
catch(sqlExceptione)
  
  
{
  
  
e.printStackTrace();
  
  
}
  
  
}
  
  

  
  
/**
  
  
*@seeHttpServlet#doPost(HttpServletRequestrequest,HttpServletResponseresponse)
  
  
*/
  
  
protectedvoiddoPost(HttpServletRequestrequest,IOException{
  
  
doGet(request,response);
  
  
}
  
  

  
  
}
 
 

项目结构如下：