java分库分表实战代码

分库分表是一种常见的水平扩展数据库的方式，可以提高数据库的性能和可扩展性。下面是一个基于Java的分库分表实战代码示例：

1. 配置数据源

在配置文件中配置多个数据源，每个数据源对应一个数据库实例，例如：

# 数据源1
db1.url=jdbc:mysql://localhost:3306/db1?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&failOverReadOnly=false&maxReconnects=10
db1.username=root
db1.password=root

# 数据源2
db2.url=jdbc:mysql://localhost:3306/db2?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&failOverReadOnly=false&maxReconnects=10
db2.username=root
db2.password=root

2. 配置MyBatis

使用MyBatis作为数据访问层框架，并配置分页插件和多数据源支持插件，例如：

<!-- 分页插件 -->
<plugins>
    <plugin interceptor="com.github.pagehelper.PageInterceptor">
        <property name="helperDialect" value="mysql"/>
        <property name="reasonable" value="true"/>
        <property name="supportMethodsArguments" value="true"/>
        <property name="params" value="pageNum=pageNumKey;pageSize=pageSizeKey;"/>
    </plugin>
    <!-- 多数据源支持插件 -->
    <plugin interceptor="com.github.mybatis.multidatasource.autoconfigure.DataSourceInterceptor">
        <property name="targetDataSources">
            <map key-type="java.lang.String">
                <entry key="db1" value-ref="db1DataSource"/>
                <entry key="db2" value-ref="db2DataSource"/>
            </map>
        </property>
    </plugin>
</plugins>

<!-- 数据源1 -->
<bean id="db1DataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
    <property name="driverClassName" value="${db1.driverClassName}"/>
    <property name="url" value="${db1.url}"/>
    <property name="username" value="${db1.username}"/>
    <property name="password" value="${db1.password}"/>
    <property name="initialSize" value="5"/>
    <property name="minIdle" value="5"/>
    <property name="maxActive" value="20"/>
    <property name="maxWait" value="60000"/>
    <property name="poolPreparedStatements" value="true"/>
    <property name="maxPoolPreparedStatementPerConnectionSize" value="20"/>
    <property name="validationQuery" value="SELECT 1 FROM DUAL"/>
    <property name="testWhileIdle" value="true"/>
    <property name="testOnBorrow" value="false"/>
    <property name="testOnReturn" value="false"/>
    <property name="filters" value="stat,wall"/>
</bean>

<!-- 数据源2 -->
<bean id="db2DataSource" class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
    <property name="driverClassName" value="${db2.driverClassName}"/>
    <property name="url" value="${db2.url}"/>
    <property name="username" value="${db2.username}"/>
    <property name="password" value="${db2.password}"/>
    <property name="initialSize" value="5"/>
    <property name="minIdle" value="5"/>
    <property name="maxActive" value="20"/>
    <property name="maxWait" value="60000"/>
    <property name="poolPreparedStatements" value="true"/>
    <property name="maxPoolPreparedStatementPerConnectionSize" value="20"/>
    <property name="validationQuery" value="SELECT 1 FROM DUAL"/>
    <property name="testWhileIdle" value="true"/>
    <property name="testOnBorrow" value="false"/>
    <property name="testOnReturn" value="false"/>
    <property name="filters" value="stat,wall"/>
</bean>

3. 配置分库分表规则

使用Sharding-JDBC作为分库分表框架，并配置分库分表规则，例如：

spring:
  shardingsphere:
    datasource:
      names: ds1,ds2
      ds1:
        url: jdbc:mysql://localhost:3306/ds1?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&failOverReadOnly=false&maxReconnects=10
        username: root
        password: root
        type: com.alibaba.druid.pool.DruidDataSource
      ds2:
        url: jdbc:mysql://localhost:3306/ds2?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&failOverReadOnly=false&maxReconnects=10
        username: root
        password: root
        type: com.alibaba.druid.pool.DruidDataSource

    sharding:
      tables:
        user:
          actualDataNodes: ds${1..2}.user_${0..1}
          tableStrategy:
            standard:
              shardingColumn: id
              shardingAlgorithmName: userTableShardingAlgorithm
          keyGenerateStrategy:
            column: id
            keyGeneratorName: snowflake
          bindingTables: user
      defaultDatabaseStrategy:
        inline:
          shardingColumn: id
          algorithmExpression: ds${id % 2 + 1}
      shardingAlgorithms:
        userTableShardingAlgorithm:
          type: INLINE
          props:
            algorithmExpression: user_${id % 2}

4. 编写代码

在代码中使用MyBatis访问数据库，并使用Sharding-JDBC进行分库分表，例如：

@Service
public class UserServiceImpl implements UserService {
    @Autowired
    private UserMapper userMapper;

    @Override
    public List<User> listUsers(int pageNum, int pageSize) {
        PageHelper.startPage(pageNum, pageSize);
        return userMapper.listUsers();
    }

    @Override
    @Transactional
    public void addUser(User user) {
        userMapper.addUser(user);
    }
}

以上就是一个基于Java的分库分表实战代码示例，具体实现方式可能因框架和需求不同而有所不同。