Hibernate/JPA如何保證不生成多餘的SQL語句？
摘要：
對SQL語句如果沒有計數和斷言的情況下，很容易失去對當前場景背後執行的SQL的控制，從而導致效能損失。
本應用是計數和斷言“幕後”觸發的SQL語句的示例。計數SQL語句非常有用，以確保您的程式碼不會生成比你預計的更多的SQL（例如，通過宣告預期語句的數量可以輕鬆檢測到N + 1）。
第...
對SQL語句如果沒有計數和斷言的情況下，很容易失去對當前場景背後執行的SQL的控制，從而導致效能損失。
本應用是計數和斷言“幕後”觸發的SQL語句的示例。計數SQL語句非常有用，以確保您的程式碼不會生成比你預計的更多的SQL（例如，通過宣告預期語句的數量可以輕鬆檢測到N + 1）。
第一步：在Maven的pom.xml中新增依賴datasource-proxy和Vlad Mihalcea的db-util：
<dependency>
<groupId>net.ttddyy</groupId>
<artifactId>datasource-proxy</artifactId>
<version>${datasource-proxy.version}</version>
</dependency>
<dependency>
<groupId>com.vladmihalcea</groupId>
<artifactId>db-util</artifactId>
<version>${db-util.version}</version>
</dependency>
第二步：使用countQuery()建立ProxyDataSourceBuilder：
@Component
<b>public</b> <b>class</b> DatasourceProxyBeanPostProcessor implements BeanPostProcessor {
<b>private</b> <b>static</b> <b>final</b> Logger logger
= Logger.getLogger(DatasourceProxyBeanPostProcessor.<b>class</b>.getName());
@Override
<b>public</b> Object postProcessAfterInitialization(Object bean, String beanName) {
<b>if</b> (bean instanceof DataSource) {
logger.info(() -> <font>"DataSource bean has been found: "</font><font> + bean);
<b>final</b> ProxyFactory proxyFactory = <b>new</b> ProxyFactory(bean);
proxyFactory.setProxyTargetClass(<b>true</b>);
proxyFactory.addAdvice(<b>new</b> ProxyDataSourceInterceptor((DataSource) bean));
<b>return</b> proxyFactory.getProxy();
}
<b>return</b> bean;
}
@Override
<b>public</b> Object postProcessBeforeInitialization(Object bean, String beanName) {
<b>return</b> bean;
}
<b>private</b> <b>static</b> <b>class</b> ProxyDataSourceInterceptor implements MethodInterceptor {
<b>private</b> <b>final</b> DataSource dataSource;
<b>public</b> ProxyDataSourceInterceptor(<b>final</b> DataSource dataSource) {
<b>super</b>();
<b>this</b>.dataSource = ProxyDataSourceBuilder.create(dataSource)
.name(</font><font>"DATA_SOURCE_PROXY"</font><font>)
.logQueryBySlf4j(SLF4JLogLevel.INFO)
.multiline()
.countQuery()
.build();
}
@Override
<b>public</b> Object invoke(<b>final</b> MethodInvocation invocation) throws Throwable {
<b>final</b> Method proxyMethod = ReflectionUtils.
findMethod(<b>this</b>.dataSource.getClass(),
invocation.getMethod().getName());
<b>if</b> (proxyMethod != <b>null</b>) {
<b>return</b> proxyMethod.invoke(<b>this</b>.dataSource, invocation.getArguments());
}
<b>return</b> invocation.proceed();
}
}
}
</font>
第三步：通過SQLStatementCountValidator.reset()重置計數器:
@SpringBootApplication
<b>public</b> <b>class</b> CountSQLStatementsApplication {
@Autowired
<b>private</b> UserService userService;
<b>public</b> <b>static</b> <b>void</b> main(String args) {
SpringApplication.run(CountSQLStatementsApplication.<b>class</b>, args);
}
@Bean
<b>public</b> ApplicationRunner init() {
<b>return</b> args -> {
userService.userOperationsWithoutTransactional();
SQLStatementCountValidator.reset();
userService.userOperationsWithTransactional();
<font><i>// allow the transaction to commit</i></font><font>
</font><font><i>// a total of 2 statements instead of 5 as in the case of no explicit transaction</i></font><font>
assertInsertCount(1);
assertUpdateCount(0);
assertDeleteCount(1);
assertSelectCount(0);
};
}
}
</font>
第四步：通過assertInsert{Update/ Delete/Select}Count(long expectedNumberOfSql斷言INSERT，UPDATE，DELETE,和SELECT：
@Service
<b>public</b> <b>class</b> UserService {
@Autowired
<b>private</b> UserRepository userRepository;
<b>public</b> <b>void</b> userOperationsWithoutTransactional() {
User user = <b>new</b> User();
user.setName(<font>"Jacky Francisco"</font><font>);
user.setCity(</font><font>"Banesti"</font><font>);
user.setAge(24);
SQLStatementCountValidator.reset();
userRepository.save(user);</font><font><i>// 1 insert</i></font><font>
user.setCity(</font><font>"Craiova"</font><font>);
userRepository.save(user);</font><font><i>// 1 update</i></font><font>
userRepository.delete(user); </font><font><i>// 1 delete</i></font><font>
</font><font><i>// at this point there is no transaction running</i></font><font>
</font><font><i>// a total of 5 statements, not very good</i></font><font>
assertInsertCount(1);
assertUpdateCount(1);
assertDeleteCount(1);
assertSelectCount(2);
}
@Transactional
<b>public</b> <b>void</b> userOperationsWithTransactional() {
User user = <b>new</b> User();
user.setName(</font><font>"Jacky Francisco"</font><font>);
user.setCity(</font><font>"Banesti"</font><font>);
user.setAge(24);
userRepository.save(user);</font><font><i>// 1 insert</i></font><font>
user.setCity(</font><font>"Craiova"</font><font>);
userRepository.save(user);</font><font><i>// update not triggered since a delete follows</i></font><font>
userRepository.delete(user); </font><font><i>// 1 delete</i></font><font>
}
}
</font>
原始碼可以在這裡 找到