JNDI（Java 命名和目錄介面）（三）---- Tomcat中配置和使用JNDI
阿新 • • 發佈：2019-02-01
JNDI是J2EE中一個很重要的標準，通常我們是在EJB程式設計中用到，
Tomcat4.0中提供了在JSP和Servelt中直接使用JNDI的方法，下面談一下在Tomcat4.0中配置和使用JNDI的方法
(以通過JNDI連線資料庫為例)
假設使用的資料庫是mysql,實驗例子在TOMCAT_HOME/webapps/DBTest目錄中
A.將mysql的JDBC連線庫mm.mysql-2.0.9-bin.jar放入TOMCAT_HOME/common/lib中
B.配置TOMCAT_HOME/conf/serer.xml檔案在<Service>;段中加入一個Context:
<Context path="/DBTest" docBase="DBTest"
debug="5" reloadable="true" crossContext="true">;
</Context>;
這是DBTest的根路徑，這是為了在DBTest中使用做準備.
C.在上面加入的<Context>;段加入
<Resource name="jdbc/TestDB"
auth="Container"
type="javax.sql.DataSource"/>;
<ResourceParams name="jdbc/TestDB">;
<parameter>;
<name>;factory</name>;
<value>;org.apache.commons.dbcp.BasicDataSourceFactory</value>;
</parameter>;
<!-- Maximum number of dB connections in pool. Make sure you
configure your mysqld max_connections large enough to handle
all of your db connections. Set to 0 for no limit.
-->;
<parameter>;
<name>;maxActive</name>;
<value>;100</value>;
</parameter>;
<!-- Maximum number of idle dB connections to retain in pool.
Set to 0 for no limit.
-->;
<parameter>;
<name>;maxIdle</name>;
<value>;30</value>;
</parameter>;
<!-- Maximum time to wait for a dB connection to become available
in ms, in this example 10 seconds. An Exception is thrown if
this timeout is exceeded. Set to -1 to wait indefinitely.
-->;
<parameter>;
<name>;maxWait</name>;
<value>;10000</value>;
</parameter>;
<!-- MySQL dB username and password for dB connections -->;
<parameter>;
<name>;username</name>;
<value>;test</value>;
</parameter>;
<parameter>;
<name>;password</name>;
<value>;test</value>;
</parameter>;
<!-- Class name for mm.mysql JDBC driver -->;
<parameter>;
<name>;driverClassName</name>;
<value>;org.gjt.mm.mysql.Driver</value>;
</parameter>;
<!-- The JDBC connection url for connecting to your MySQL dB.-->;
<parameter>;
<name>;url</name>;
<value>;jdbc:mysql://localhost:3306/test</value>;
</parameter>;
</ResourceParams>;
這裡每一個小段都有英文註解，是Tomcat提供的，我們可以將按照Sample加入,主要修改的是driverClassName,
url,和使用者帳號;需要強調的是"jdbc/TestDB"就是JDNI要查詢的Name.
D. 在JSPh或servlet中使用JNDI查詢服務
下面是在JSP檔案中關於JNDI使用的程式碼(檔名記為UserHandleDB.jsp)
需要注意的是JNDI NAME要在前面加上"java:comp/env/"
<%@ page language="java"%>;
<%@ page import="java.util.*" %>;
<%@ page import="java.sql.*" %>;
<%@ page import="javax.sql.*" %>;
<%@ page import="javax.naming.*" %>;
<%
String jndi_name="java:comp/env/jdbc/TestDB";
String select_user_sql="select userid,name,birthday, email from emp";
String colnames[][]={{"User ID","Name","Birth day","EMail"},
{"userid","name","birthday","email"}};
Vector userSet=new Vector();
Vector columnSet=new Vector();
for(int i=0;i<colnames[0].length;i++){
columnSet.add(colnames[0]);
userSet.add(columnSet);
Context ctx = new InitialContext();
if(ctx == null )
throw new Exception("No Context");
DataSource ds = (DataSource)ctx.lookup(jndi_name);
Connection conn = ds.getConnection();
try {
PreparedStatement psPreparedStatement=conn.prepareStatement(select_user_sql);
ResultSet resultSet = psPreparedStatement.executeQuery();
while(resultSet.next()){
columnSet=new Vector();
for(int i=0;i<colnames[1].length;i++){
columnSet.add(resultSet.getString(colnames[1]));
}
userSet.add(columnSet);
}
}catch(SQLException e) {
e.printStackTrace();
}finally {
conn.close();
%>;
E. 引用UserHandleDB.jsp(記為ViewTable.jsp)
<html>;
<head>;
<title>;Test Database </title>;
<body >;
<%@ include file="UserHandleDB.jsp" %>;
<table border="1" >;
<%
for(int i=0;i<userSet.size();i++){
Vector colSet=(Vector)userSet.get(i);
out.print("<tr>;");
for(int j=0;j<colSet.size();j++){
String col=(String)colSet.get(j);
out.print("<td>;"+col+"</td>;");
}
out.print("</tr>;");
}
%>;
</table>;
</body>;
</html>;
F. 在web.xml中加入
<resource-ref>;
<description>;DB Connection</description>;
<res-ref-name>;jdbc/TestDB</res-ref-name>;
<res-type>;javax.sql.DataSource</res-type>;
<res-auth>;Container</res-auth>;
</resource-ref>;
這裡的jdbc/TestDb要和C中Resource段的name匹配
G. 觀察結果
首先確定資料庫已經啟動，接著啟動Tomcat，如果Tomcat啟動異常，可能的原因是資料庫的JDBC庫沒有載入
最後開啟瀏覽器，訪問 http://localhost:8080/DBTest/ViewTable.jsp就可以看到結果
Tomcat4.0中提供了在JSP和Servelt中直接使用JNDI的方法，下面談一下在Tomcat4.0中配置和使用JNDI的方法
(以通過JNDI連線資料庫為例)
假設使用的資料庫是mysql,實驗例子在TOMCAT_HOME/webapps/DBTest目錄中
A.將mysql的JDBC連線庫mm.mysql-2.0.9-bin.jar放入TOMCAT_HOME/common/lib中
B.配置TOMCAT_HOME/conf/serer.xml檔案在<Service>;段中加入一個Context:
<Context path="/DBTest" docBase="DBTest"
debug="5" reloadable="true" crossContext="true">;
</Context>;
這是DBTest的根路徑，這是為了在DBTest中使用做準備.
C.在上面加入的<Context>;段加入
<Resource name="jdbc/TestDB"
auth="Container"
type="javax.sql.DataSource"/>;
<ResourceParams name="jdbc/TestDB">;
<parameter>;
<name>;factory</name>;
<value>;org.apache.commons.dbcp.BasicDataSourceFactory</value>;
</parameter>;
<!-- Maximum number of dB connections in pool. Make sure you
configure your mysqld max_connections large enough to handle
all of your db connections. Set to 0 for no limit.
-->;
<parameter>;
<name>;maxActive</name>;
<value>;100</value>;
</parameter>;
<!-- Maximum number of idle dB connections to retain in pool.
Set to 0 for no limit.
-->;
<parameter>;
<name>;maxIdle</name>;
<value>;30</value>;
</parameter>;
<!-- Maximum time to wait for a dB connection to become available
in ms, in this example 10 seconds. An Exception is thrown if
this timeout is exceeded. Set to -1 to wait indefinitely.
-->;
<parameter>;
<name>;maxWait</name>;
<value>;10000</value>;
</parameter>;
<!-- MySQL dB username and password for dB connections -->;
<parameter>;
<name>;username</name>;
<value>;test</value>;
</parameter>;
<parameter>;
<name>;password</name>;
<value>;test</value>;
</parameter>;
<!-- Class name for mm.mysql JDBC driver -->;
<parameter>;
<name>;driverClassName</name>;
<value>;org.gjt.mm.mysql.Driver</value>;
</parameter>;
<!-- The JDBC connection url for connecting to your MySQL dB.-->;
<parameter>;
<name>;url</name>;
<value>;jdbc:mysql://localhost:3306/test</value>;
</parameter>;
</ResourceParams>;
這裡每一個小段都有英文註解，是Tomcat提供的，我們可以將按照Sample加入,主要修改的是driverClassName,
url,和使用者帳號;需要強調的是"jdbc/TestDB"就是JDNI要查詢的Name.
D. 在JSPh或servlet中使用JNDI查詢服務
下面是在JSP檔案中關於JNDI使用的程式碼(檔名記為UserHandleDB.jsp)
需要注意的是JNDI NAME要在前面加上"java:comp/env/"
<%@ page language="java"%>;
<%@ page import="java.util.*" %>;
<%@ page import="java.sql.*" %>;
<%@ page import="javax.sql.*" %>;
<%@ page import="javax.naming.*" %>;
<%
String jndi_name="java:comp/env/jdbc/TestDB";
String select_user_sql="select userid,name,birthday, email from emp";
String colnames[][]={{"User ID","Name","Birth day","EMail"},
{"userid","name","birthday","email"}};
Vector userSet=new Vector();
Vector columnSet=new Vector();
for(int i=0;i<colnames[0].length;i++){
columnSet.add(colnames[0]);
userSet.add(columnSet);
Context ctx = new InitialContext();
if(ctx == null )
throw new Exception("No Context");
DataSource ds = (DataSource)ctx.lookup(jndi_name);
Connection conn = ds.getConnection();
try {
PreparedStatement psPreparedStatement=conn.prepareStatement(select_user_sql);
ResultSet resultSet = psPreparedStatement.executeQuery();
while(resultSet.next()){
columnSet=new Vector();
for(int i=0;i<colnames[1].length;i++){
columnSet.add(resultSet.getString(colnames[1]));
}
userSet.add(columnSet);
}
}catch(SQLException e) {
e.printStackTrace();
}finally {
conn.close();
%>;
E. 引用UserHandleDB.jsp(記為ViewTable.jsp)
<html>;
<head>;
<title>;Test Database </title>;
<body >;
<%@ include file="UserHandleDB.jsp" %>;
<table border="1" >;
<%
for(int i=0;i<userSet.size();i++){
Vector colSet=(Vector)userSet.get(i);
out.print("<tr>;");
for(int j=0;j<colSet.size();j++){
String col=(String)colSet.get(j);
out.print("<td>;"+col+"</td>;");
}
out.print("</tr>;");
}
%>;
</table>;
</body>;
</html>;
F. 在web.xml中加入
<resource-ref>;
<description>;DB Connection</description>;
<res-ref-name>;jdbc/TestDB</res-ref-name>;
<res-type>;javax.sql.DataSource</res-type>;
<res-auth>;Container</res-auth>;
</resource-ref>;
這裡的jdbc/TestDb要和C中Resource段的name匹配
G. 觀察結果
首先確定資料庫已經啟動，接著啟動Tomcat，如果Tomcat啟動異常，可能的原因是資料庫的JDBC庫沒有載入
最後開啟瀏覽器，訪問 http://localhost:8080/DBTest/ViewTable.jsp就可以看到結果