H2資料庫是一種由Java編寫的，極小，速度極快，可嵌入式的資料庫。非常適合用在單元測試等資料不需要儲存的場景下面。
以下時其官網的介紹：
{% blockquote h2 http://www.h2database.com/html/main.html h2 %}
Welcome to H2, the Java SQL database. The main features of H2 are:
Very fast, open source, JDBC API
Embedded and server modes; in-memory databases
Browser based Console application

spring-data直連測試

我們使用的maven工程來搭建測試環境，工程目錄如下：

程式碼裡面資料庫對映使用了spring-data 和 Hibernate實現，方便實現，避免自己寫sql。

資料連線配置資訊

jdbc.driver=net.sf.log4jdbc.DriverSpy
jdbc.url=jdbc:log4jdbc:h2:mem:test;MODE=MySql;DB_CLOSE_DELAY=-1
jdbc.username=sa
jdbc.password=
 

引數解析：

1. driver這裡我用的時log4jdbc這個專案，可以方便的打印出帶全部引數的sql
2. jdbc:h2:mem 意思使用h2的記憶體資料庫版本，還可以有file等各種方式
3. test連線的資料庫名稱
4. MODE=MySql 以mysql的模式執行
5. DB_CLOSE_DELAY=-1 關閉引數，延時關閉為程式碼退出時間。

測試用例：

    @Test
    publicvoidtestFindAll() {
        List<User> list = (List<User>) userDao.findAll();
        for (User user : list) {
            System.out
 
.println(user.toString());
        }
    }

執行結果：

17:45:37.582 [main] INFO  o.s.jdbc.datasource.init.ScriptUtils - Executing SQL script from class path resource [db/sql/schema.sql]
17:45:37.587 [main] INFO  jdbc.sqltiming - DROP TABLE IF EXISTS sys_user
 {executed in 0 msec}
17:45:37.593 [main] INFO  jdbc.sqltiming - CREATE TABLE sys_user ( id BIGINT NOT NULL, name VARCHAR(255), PRIMARY KEY (id) )
 {executed in 5 msec}
17:45:37.594 [main] INFO  o.s.jdbc.datasource.init.ScriptUtils - Executed SQL script from class path resource [db/sql/schema.sql] in 10 ms.
17:45:37.594 [main] INFO  o.s.jdbc.datasource.init.ScriptUtils - Executing SQL script from class path resource [db/sql/import-data.sql]
17:45:37.596 [main] INFO  jdbc.sqltiming - INSERT INTO sys_user (id, name) VALUES (1111, '張三')
 {executed in 1 msec}
17:45:37.597 [main] INFO  o.s.jdbc.datasource.init.ScriptUtils - Executed SQL script from class path resource [db/sql/import-data.sql] in 3 ms.
17:45:37.598 [main] INFO  jdbc.connection - 2. Connection closed
17:45:37.756 [main] INFO  jdbc.connection - 3. Connection opened
17:45:37.758 [main] INFO  o.s.t.c.t.TransactionContext - Began transaction (1) for test context [[email protected] testClass = UserDaoTest, testInstance = [email protected]6482eef, testMethod = [email protected], testException = [null], mergedContextConfiguration = [[email protected]2ab2710 testClass = UserDaoTest, locations = '{classpath:/applicationContext.xml}', classes = '{}', contextInitializerClasses = '[]', activeProfiles = '{test}', propertySourceLocations = '{}', propertySourceProperties = '{}', contextLoader = 'org.springframework.test.context.support.DelegatingSmartContextLoader', parent = [null]]]; transaction manager [org.springframework.orm.jpa.JpaTransactionManager[email protected]]; rollback [true]
17:45:37.879 [main] INFO  jdbc.sqltiming - select user0_.id as id1_0_, user0_.name as name2_0_ from sys_user user0_
 {executed in 0 msec}
User{id=1111, name='張三'}
17:45:37.906 [main] INFO  jdbc.connection - 3. Connection closed

測試通過，H2搭建測試環境成功。

新增schema

2.0版本新增資料庫跨庫查詢；

@Entity
@Table(name = "sys_user",schema = "sys")
public class User implements Serializable {
    private Long id;
    private String name;
    //省略getter和setter方法
}

sql同時也要修改為：

CREATE SCHEMA IF NOT EXISTS sys;

DROP TABLE IF EXISTS sys.sys_user;

CREATE TABLE sys.sys_user (
  id   BIGINT NOT NULL,
  name VARCHAR(255),
  PRIMARY KEY (id)
)

INSERT INTO sys.sys_user (id, name) VALUES (1111, '張三');

jdbc連線的url不變。
執行測試用例，結果完全一致：

17:56:58.160 [main] INFO  o.s.jdbc.datasource.init.ScriptUtils - Executing SQL script from class path resource [db/sql/schema.sql]
17:56:58.165 [main] INFO  jdbc.sqltiming - CREATE SCHEMA IF NOT EXISTS sys
 {executed in 0 msec}
17:56:58.165 [main] INFO  jdbc.sqltiming - DROP TABLE IF EXISTS sys.sys_user
 {executed in 0 msec}
17:56:58.170 [main] INFO  jdbc.sqltiming - CREATE TABLE sys.sys_user ( id BIGINT NOT NULL, name VARCHAR(255), PRIMARY KEY (id) )
 {executed in 4 msec}
17:56:58.170 [main] INFO  o.s.jdbc.datasource.init.ScriptUtils - Executed SQL script from class path resource [db/sql/schema.sql] in 10 ms.
17:56:58.170 [main] INFO  o.s.jdbc.datasource.init.ScriptUtils - Executing SQL script from class path resource [db/sql/import-data.sql]
17:56:58.172 [main] INFO  jdbc.sqltiming - INSERT INTO sys.sys_user (id, name) VALUES (1111, '張三')
 {executed in 1 msec}
17:56:58.172 [main] INFO  o.s.jdbc.datasource.init.ScriptUtils - Executed SQL script from class path resource [db/sql/import-data.sql] in 2 ms.
17:56:58.318 [main] INFO  o.s.t.c.t.TransactionContext - Began transaction (1) for test context [[email protected] testClass = UserDaoTest, testInstance = [email protected]6482eef, testMethod = [email protected], testException = [null], mergedContextConfiguration = [[email protected]2ab2710 testClass = UserDaoTest, locations = '{classpath:/applicationContext.xml}', classes = '{}', contextInitializerClasses = '[]', activeProfiles = '{test}', propertySourceLocations = '{}', propertySourceProperties = '{}', contextLoader = 'org.springframework.test.context.support.DelegatingSmartContextLoader', parent = [null]]]; transaction manager [[email protected]]; rollback [true]
17:56:58.431 [main] INFO  jdbc.sqltiming - select user0_.id as id1_0_, user0_.name as name2_0_ from sys.sys_user user0_
 {executed in 1 msec}
User{id=1111, name='張三'}
17:56:58.451 [main] INFO  jdbc.connection - 3. Connection closed

schema新增後，只需要將對應的建立表和語句對應修改即可。