java - 无法使用来自同一应用程序的 jndi 名称切换到不同的数据源

Question

我在java中遇到了一些关于数据源切换的问题。我已经编写了数据源查找的代码，即使我的应用程序采用了我的属性文件中给出的默认jndi名称。我想让用户访问不同的数据库。 .但是我无法使用jndi名称切换到不同的数据源..请帮助编写以下代码以进行数据源查找........

Context ctx = new InitialContext();
if (dataSource == null) 
{
 dataSource = (DataSource) ctx.lookup(jndi_name);
}

Answer 1

这是我在我的项目中所做的。我正在使用 Tomcat、Servlet 和 mysql 数据库。在 tomcat 中有 server.xml 文件，我们需要粘贴以下详细信息并保存并重新启动 tomcat。在 servlet 应用程序中，我们需要两个 jndi，使用此代码 dataSource = (DataSource) ctx.lookup(jndi_name); } jndi_name 是不同的，然后尝试。

  <Resource name="jdbc/name(any name --this will use in project(jndi)" auth="Container" type="javax.sql.DataSource"/>

  <ResourceParams name="jdbc/name(same)">
    <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>database username</value>
    </parameter>
    <parameter>
     <name>password</name>
     <value>database password</value>
    </parameter>

    <!-- Class name for MYSQL JDBC driver -->
    <parameter>
       <name>driverClassName</name>
       <value>com.mysql.jdbc.Driver</value>
    </parameter>

    <!-- The JDBC connection url for connecting to your MySQL dB.
     The autoReconnect=true argument to the url makes sure that the
     mm.mysql JDBC Driver will automatically reconnect if mysqld closed the
     connection.  mysqld by default closes idle connections after 8 hours.
     -->
    <parameter>
      <name>url</name>
      <value>jdbc:mysql://localhost:3306/database Name</value>
    </parameter>    

    <parameter>
      <name>validationQuery</name>
      <value>SELECT 1</value>
    </parameter>

  </ResourceParams> 

<Resource name="jdbc/name1" auth="Container" type="javax.sql.DataSource"/>

  <ResourceParams name="jdbc/name1">
    <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>database username</value>
    </parameter>
    <parameter>
     <name>password</name>
     <value>database Password</value>
    </parameter>
    <!-- Class name for MYSQL JDBC driver -->
    <parameter>
       <name>driverClassName</name>
       <value>com.mysql.jdbc.Driver</value>
    </parameter>

     <parameter>
      <name>url</name>
      <value>jdbc:mysql://localhost:3306/another databasename</value>
    </parameter>    

    <parameter>
      <name>validationQuery</name>
      <value>SELECT 1</value>
    </parameter>

  </ResourceParams> 

</Context>