RowHandler

最新推荐文章于 2022-05-26 10:13:01 发布

headays

最新推荐文章于 2022-05-26 10:13:01 发布

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CC 4.0 BY-SA版权

文章标签： string encoding user jdbc exception ibatis

本文链接：https://blog.youkuaiyun.com/headays/article/details/6455903

本文展示了如何使用iBatis的RowHandler处理大量数据库记录，并将其导出到txt文件中。通过创建User类，配置SQL映射文件和数据源，最后实现RowHandler接口将查询结果写入文件。

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今天写了一段代码就是将数据库中几万条记录查出来写到一个txt文件中！我使用了ibatis，就在发现rowhandler能够处理超大数据集！就写了一个测试文件和大家一起分享一下！

1.写了一个User类

package com.test.bean;

public class User {

private int id;
private String username;
private String password;

public int getId() {
  return id;
}
public void setId(int id) {
  this.id = id;
}
public String getUsername() {
  return username;
}
public void setUsername(String username) {
  this.username = username;
}
public String getPassword() {
  return password;
}
public void setPassword(String password) {
  this.password = password;
}

}

2.新建一个user.xml,写入一个查询语句

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sqlMap
PUBLIC "-//iBATIS.com//DTD SQL Map 2.0//EN"
"http://www.ibatis.com/dtd/sql-map-2.dtd">
<sqlMap namespace="user">
<typeAlias alias="user" type="com.test.bean.User"/>
<select id="getUser" resultClass="java.util.HashMap">
  <![CDATA[
   select * from tb_user
  ]]>
</select>
</sqlMap>

3.新建一个sqlmap-config.xml，在里边配置数据源等信息，并且引入user.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sqlMapConfig
PUBLIC "-//iBATIS.com//DTD SQL Map Config 2.0//EN"
"http://www.ibatis.com/dtd/sql-map-config-2.dtd">
<sqlMapConfig>
<settings
cacheModelsEnabled="true"
enhancementEnabled="true"
lazyLoadingEnabled="true"
errorTracingEnabled="true"
maxRequests="32"
maxSessions="10"
maxTransactions="5"
useStatementNamespaces="false"
/>
<transactionManager type="JDBC">
  <dataSource type="SIMPLE">
   <property name="JDBC.Driver" value="com.mysql.jdbc.Driver"/>
   <property name="JDBC.ConnectionURL" value="jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8"/>
   <property name="JDBC.Username" value="root"/>
   <property name="JDBC.Password" value="root"/>
   <property name="Pool.MaximumActiveConnections" value="10"/>
   <property name="Pool.MaximumIdleConnections" value="5"/>
   <property name="Pool.MaximumCheckoutTime" value="120000"/>
   <property name="Pool.TimeToWait" value="500"/>
   <property name="Pool.PingQuery" value="select 1 from ACCOUNT"/>
   <property name="Pool.PingEnabled" value="false"/>
   <property name="Pool.PingConnectionsOlderThan" value="1"/>
   <property name="Pool.PingConnectionsNotUsedFor" value="1"/>
  </dataSource>
</transactionManager>
<sqlMap resource="com/test/config/user.xml"/>
</sqlMapConfig>

4.新建一个测试文件RowHandlerTest.java

public class RowHandlerTest extends TestCase implements RowHandler{

StringBuilder s = new StringBuilder();
public void testRowHandler() throws Exception{

  String resource = "com/test/config/sqlmap-config.xml";
  Reader reader = Resources.getResourceAsReader(resource);
  SqlMapClient sqlMapClient = SqlMapClientBuilder.buildSqlMapClient(reader);

  RowHandlerTest rht = new RowHandlerTest();
  sqlMapClient.queryWithRowHandler("getUser", null, rht);
  StringBuilder s = rht.getXmlDocument();
  String dirPath = "D:"+File.separatorChar;
  File file = new File(dirPath,"test.txt");
  FileUtils.writeStringToFile(file, s.toString());
}
  public void handleRow(Object o) {
  Map map = (Map)o;
  s.append(map.get("id"));
  s.append("/t");
  s.append(map.get("username"));
  s.append("/t");
  s.append(map.get("password"));
  s.append("/r/n");
}
public StringBuilder getXmlDocument() {
  return s;
}
}