commons-dbutils是Apache开源组织提供的用于操作数据库的工具包。今天为大家介绍一下该包的常用方法。
对于数据库的操作无外乎增删改查，而增删改本质上可以归为一类，操作方式相同，只是SQL语法不同而已，所以我将以修改和查询两类来介绍commons-dbutils的用法。
首先我们来创建一个测试类，使用JUnit进行测试。
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import org.apache.commons.dbutils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
public class DBUtilsTest
{
private Connection conn = null;
@Before
public void initConnection() throws SQLException, ClassNotFoundException
{
printCurrentMethodName();
Class.forName("org.h2.Driver");
conn = DriverManager.getConnection("jdbc:h2:h2.db", "test", "123");
}
@Before
public void initDatabase() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
runner.update(
conn,
"CREATE TABLE IF NOT EXISTS USER_INFO (userId VARCHAR(20) PRIMARY KEY, userName VARCHAR(50))");
}
@After
public void destory()
{
printCurrentMethodName();
DbUtils.closeQuietly(conn);
}
/**
* 打印当前运行方法名称
*/
public void printCurrentMethodName()
{
System.out.println(Thread.currentThread().getStackTrace()[2]
.getMethodName());
System.out.println("==================================================");
}
}
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在这段测试代码中，我们是用h2作为数据库进行测试以及定义了一些连接、数据库的初始化及销毁的方法。
在commons-dbutils中操作数据库的常用类为：QueryRunner。 QueryRunner的常用方法如下：
| 返回值 | 方法名 | 说明 |
|---|---|---|
| int[] | batch(Connection conn, String sql, Object[][] params) | 批量执行INSERT、UPDATE或DELETE |
| int[] | batch(String sql, Object[][] params) | 批量执行INSERT、UPDATE或DELETE |
| T | insert(Connection conn, String sql, ResultSetHandler rsh) | 执行一个插入查询语句 |
| T | insert(Connection conn, String sql, ResultSetHandler rsh, Object… params) | 执行一个插入查询语句 |
| T | insert(String sql, ResultSetHandler rsh) | 执行一个插入查询语句 |
| T | insert(String sql, ResultSetHandler rsh, Object… params) | 执行一个插入查询语句 |
| T | insertBatch(Connection conn, String sql, ResultSetHandler rsh, Object[][] params) | 批量执行插入语句 |
| T | insertBatch(String sql, ResultSetHandler rsh, Object[][] params) | 批量执行插入语句 |
| T | query(Connection conn, String sql, ResultSetHandler rsh) | 查询 |
| T | query(Connection conn, String sql, ResultSetHandler rsh, Object… params) | 查询 |
| T | query(String sql, ResultSetHandler rsh) | 查询 |
| T | query(String sql, ResultSetHandler rsh, Object… params) | 查询 |
| int | update(Connection conn, String sql) | 执行INSERT、UPDATE或DELETE |
| int | update(Connection conn, String sql, Object… params) | 执行INSERT、UPDATE或DELETE |
| int | update(Connection conn, String sql, Object param) | 执行INSERT、UPDATE或DELETE |
| int | update(String sql) | 执行INSERT、UPDATE或DELETE |
| int | update(String sql, Object… params) | 执行INSERT、UPDATE或DELETE |
| int | update(String sql, Object param) | 执行INSERT、UPDATE或DELETE |
修改
我们先来看一下如何使用QueryRunner进行修改操作，在我们的测试代码中添加测试方法：
@Test
public void update() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
String suffix = Long.toHexString(System.currentTimeMillis());
Integer result = runner.update(conn,
"insert into USER_INFO(userId, userName) values(?, ?)", suffix,
"name" + suffix);
System.out.println("受影响记录条数：" + result);
}
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修改的操作相比较而言还是很简单的，在这段测试代码中，我们向数据库中添加了一条记录，在QueryRunner中也是支持动态参数的，可以很方便的绑定参数。
查询
ScalarHandler
ScalarHandler会返回一个对象，用于读取结果集中第一行指定列的数据。这里我们以查询表中总记录数为例：
@Test
public void queryByScalarHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
Number number = runner.query(conn, "select count(*) from USER_INFO",
new ScalarHandler<Number>());
System.out.println("总记录记录条数：" + number.intValue());
}
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不知大家有没有发现，在ScalarHandler的泛型中，我使用的是Number，解释一下：之前我在使用该方法查询记录条数的时候，不同的数据库返回的数据类型可能不同，有的返回是Integer，而有的却是Long，为了代码的通用，所以在这里我使用了Number。
ArrayHandler
ArrayHandler会返回一个数组，用于将结果集第一行数据转换为数组。
@Test
public void queryByArrayHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
Object[] results = runner.query(conn, "select * from USER_INFO",
new ArrayHandler());
System.out.println(Arrays.asList(results));
}
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ArrayListHandler
ArrayListHandler会返回一个集合，集合中的每一项对应结果集指定行中的数据转换后的数组。
@Test
public void queryByArrayListHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
List<Object[]> results = runner.query(conn, "select * from USER_INFO",
new ArrayListHandler());
for (Object[] object : results)
{
System.out.println(Arrays.asList(object));
}
}
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KeyedHandler
KeyedHandler会返回一个Map，我们可以指定某一列的值作为该Map的键，Map中的值为对应行数据转换的键值对，键为列名。
@Test
public void queryByKeyedHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
Map<String, Map<String, Object>> results = runner.query(conn,
"select * from USER_INFO", new KeyedHandler<String>());
System.out.println(results);
}
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ColumnListHandler
ColumnListHandler会返回一个集合，集合中的数据为结果集中指定列的数据。
@Test
public void queryByColumnListHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
List<String> results = runner.query(conn, "select * from USER_INFO",
new ColumnListHandler<String>());
System.out.println(results);
}
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MapHandler
MapHandler会将结果集中第一行数据转换为键值对，键为列名。
@Test
public void queryByMapHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
Map<String, Object> results = runner.query(conn,
"select * from USER_INFO", new MapHandler());
System.out.println(results);
}
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MapListHandler
MapHandler会将结果集中的数据转换为一个集合，集合中的数据为对应行转换的键值对，键为列名
@Test
public void queryByMapListHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
List<Map<String, Object>> results = runner.query(conn,
"select * from USER_INFO", new MapListHandler());
System.out.println(results);
}
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BeanHandler
BeanHandler实现了将结果集第一行数据转换为Bean对象，在实际应用中非常方便。
在编写测试代码之前，我们先来编写一个对应的Bean类：
import java.text.MessageFormat;
public class UserInfo
{
private String userId;
private String userName;
public String getUserId()
{
return userId;
}
public void setUserId(String userId)
{
this.userId = userId;
}
public String getUserName()
{
return userName;
}
public void setUserName(String userName)
{
this.userName = userName;
}
@Override
public String toString()
{
return MessageFormat
.format("[userId:{0},userName:{1}]", userId, userName);
}
}
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接下来，我们来编写测试代码：
@Test
public void queryByBeanHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
UserInfo results = runner.query(conn, "select * from USER_INFO",
new BeanHandler<UserInfo>(UserInfo.class));
System.out.println(results);
}
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BeanListHandler
BeanHandler只转换结果集的第一行，而BeanListHandler会将结果集的所有行进行转换，返回一个集合。
@Test
public void queryByBeanListHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
List<UserInfo> results = runner.query(conn, "select * from USER_INFO",
new BeanListHandler<UserInfo>(UserInfo.class));
System.out.println(results);
}
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BeanMapHandler
BeanMapHandler也会将结果集转换为Bean对象，不过返回的是已指定列的值作为键的键值对。
@Test
public void queryByBeanMapHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
Map<String, UserInfo> results = runner.query(conn,
"select * from USER_INFO", new BeanMapHandler<String, UserInfo>(
UserInfo.class));
System.out.println(results);
}
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完整测试代码
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import org.apache.commons.dbutils.DbUtils;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.ArrayHandler;
import org.apache.commons.dbutils.handlers.ArrayListHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.BeanMapHandler;
import org.apache.commons.dbutils.handlers.ColumnListHandler;
import org.apache.commons.dbutils.handlers.KeyedHandler;
import org.apache.commons.dbutils.handlers.MapHandler;
import org.apache.commons.dbutils.handlers.MapListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import org.junit.After;
import org.junit.Before;
public class DBUtilsTest
{
private Connection conn = null;
@Before
public void initConnection() throws SQLException, ClassNotFoundException
{
printCurrentMethodName();
Class.forName("org.h2.Driver");
conn = DriverManager.getConnection("jdbc:h2:h2.db", "test", "123");
}
@Before
public void initDatabase() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
runner.update(
conn,
"CREATE TABLE IF NOT EXISTS USER_INFO (userId VARCHAR(20) PRIMARY KEY, userName VARCHAR(50))");
}
public void update() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
String suffix = Long.toHexString(System.currentTimeMillis());
Integer result = runner.update(conn,
"insert into USER_INFO(userId, userName) values(?, ?)", suffix,
"name" + suffix);
System.out.println("受影响记录条数：" + result);
}
public void queryByScalarHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
Number number = runner.query(conn, "select count(*) from USER_INFO",
new ScalarHandler<Number>());
System.out.println("总记录记录条数：" + number.intValue());
}
public void queryByArrayHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
Object[] results = runner.query(conn, "select * from USER_INFO",
new ArrayHandler());
System.out.println(Arrays.asList(results));
}
public void queryByArrayListHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
List<Object[]> results = runner.query(conn, "select * from USER_INFO",
new ArrayListHandler());
for (Object[] object : results)
{
System.out.println(Arrays.asList(object));
}
}
public void queryByKeyedHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
Map<String, Map<String, Object>> results = runner.query(conn,
"select * from USER_INFO", new KeyedHandler<String>());
System.out.println(results);
}
public void queryByColumnListHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
List<String> results = runner.query(conn, "select * from USER_INFO",
new ColumnListHandler<String>());
System.out.println(results);
}
public void queryByMapHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
Map<String, Object> results = runner.query(conn,
"select * from USER_INFO", new MapHandler());
System.out.println(results);
}
public void queryByMapListHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
List<Map<String, Object>> results = runner.query(conn,
"select * from USER_INFO", new MapListHandler());
System.out.println(results);
}
public void queryByBeanHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
UserInfo results = runner.query(conn, "select * from USER_INFO",
new BeanHandler<UserInfo>(UserInfo.class));
System.out.println(results);
}
public void queryByBeanListHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
List<UserInfo> results = runner.query(conn, "select * from USER_INFO",
new BeanListHandler<UserInfo>(UserInfo.class));
System.out.println(results);
}
public void queryByBeanMapHandler() throws SQLException
{
printCurrentMethodName();
QueryRunner runner = new QueryRunner();
Map<String, UserInfo> results = runner.query(conn,
"select * from USER_INFO", new BeanMapHandler<String, UserInfo>(
UserInfo.class));
System.out.println(results);
}
@After
public void destory()
{
printCurrentMethodName();
DbUtils.closeQuietly(conn);
}
/**
* 打印当前运行方法名称
*/
public void printCurrentMethodName()
{
System.out.println(Thread.currentThread().getStackTrace()[2]
.getMethodName());
System.out.println("==================================================");
}
}
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