1. 前言

Druid數(shù)據(jù)庫連接池由阿里巴巴開源，號稱是java語言中最好的數(shù)據(jù)庫連接池，是為監(jiān)控而生的。Druid的官方地址是：https://github.com/alibaba/druid

通過本文，我們可以看到

• Spring Boot 如何配置數(shù)據(jù)源
• Spring Boot 如何集成Druid數(shù)據(jù)庫連接池
• 如何打開并訪問Druid數(shù)據(jù)庫連接池的監(jiān)控功能
• Spring Boot 使用JdbcTemplate操作數(shù)據(jù)庫

2. 配置pom.xml

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.3.5.RELEASE</version>
</parent>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version>1.8</java.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-jdbc</artifactId>
    </dependency>
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>1.0.20</version>
    </dependency>
    <dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
        <scope>runtime</scope>
    </dependency>
</dependencies>

3. 在application.properties中配置數(shù)據(jù)源

# 數(shù)據(jù)庫訪問配置，此處使用postgres為例。
# 主數(shù)據(jù)源，默認的
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.datasource.driver-class-name=org.postgresql.Driver
spring.datasource.url=jdbc:postgresql://192.168.1.9/jianshudb
spring.datasource.username=postgres
spring.datasource.password=yourpassword

# 下面為連接池的補充設(shè)置，應(yīng)用到上面所有數(shù)據(jù)源中
# 初始化大小，最小，最大
spring.datasource.initialSize=5
spring.datasource.minIdle=5
spring.datasource.maxActive=20
# 配置獲取連接等待超時的時間
spring.datasource.maxWait=60000
# 配置間隔多久才進行一次檢測，檢測需要關(guān)閉的空閑連接，單位是毫秒 
spring.datasource.timeBetweenEvictionRunsMillis=60000
# 配置一個連接在池中最小生存的時間，單位是毫秒 
spring.datasource.minEvictableIdleTimeMillis=300000
# Oracle請使用select 1 from dual
spring.datasource.validationQuery=SELECT 'x'
spring.datasource.testWhileIdle=true
spring.datasource.testOnBorrow=false
spring.datasource.testOnReturn=false
# 打開PSCache，并且指定每個連接上PSCache的大小 
spring.datasource.poolPreparedStatements=true
spring.datasource.maxPoolPreparedStatementPerConnectionSize=20
# 配置監(jiān)控統(tǒng)計攔截的filters，去掉后監(jiān)控界面sql無法統(tǒng)計，'wall'用于防火墻 
spring.datasource.filters=stat,wall,slf4j
# 通過connectProperties屬性來打開mergeSql功能；慢SQL記錄
#spring.datasource.connectionProperties=druid.stat.mergeSql=true;druid.stat.slowSqlMillis=5000
# 合并多個DruidDataSource的監(jiān)控數(shù)據(jù)
#spring.datasource.useGlobalDataSourceStat=true

DruidDataSource參考配置：
https://github.com/alibaba/druid/wiki/%E9%85%8D%E7%BD%AE_DruidDataSource%E5%8F%82%E8%80%83%E9%85%8D%E7%BD%AE

4. 打開Druid的監(jiān)控統(tǒng)計功能

Druid的監(jiān)控統(tǒng)計功能是通過filter-chain擴展實現(xiàn)，如果你要打開監(jiān)控統(tǒng)計功能，需要配置StatFilter，相關(guān)代碼如下。

@Configuration
public class DruidConfiguration {

  private static final Logger log = LoggerFactory.getLogger(DruidConfiguration.class);

  @Bean
  public ServletRegistrationBean druidServlet() {
    log.info("init Druid Servlet Configuration ");
    ServletRegistrationBean servletRegistrationBean = new ServletRegistrationBean();
    servletRegistrationBean.setServlet(new StatViewServlet());
    servletRegistrationBean.addUrlMappings("/druid/*");
    Map<String, String> initParameters = new HashMap<String, String>();
    initParameters.put("loginUsername", "admin");// 用戶名
    initParameters.put("loginPassword", "admin");// 密碼
    initParameters.put("resetEnable", "false");// 禁用HTML頁面上的“Reset All”功能
    initParameters.put("allow", ""); // IP白名單 (沒有配置或者為空，則允許所有訪問)
    //initParameters.put("deny", "192.168.20.38");// IP黑名單 (存在共同時，deny優(yōu)先于allow)
    servletRegistrationBean.setInitParameters(initParameters);
    return servletRegistrationBean;
  }

  @Bean
  public FilterRegistrationBean filterRegistrationBean() {
    FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
    filterRegistrationBean.setFilter(new WebStatFilter());
    filterRegistrationBean.addUrlPatterns("/*");
    filterRegistrationBean.addInitParameter("exclusions", "*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*");
    return filterRegistrationBean;
  }

}

等應(yīng)用啟動后，可以訪問地址：http://localhost:8080/druid/，用戶名和密碼見上述代碼中的設(shè)置，即admin/admin。

5. 使用JdbcTemplate操作數(shù)據(jù)庫

假設(shè)數(shù)據(jù)庫中有表t_user,其中id=1的user的username為ZhangSan。下面的例子演示了通過id查找username的情況。

@RestController
public class DemoController {

    @Autowired
    JdbcTemplate jdbcTemplate;

    @RequestMapping(value = "/hello.do", method = RequestMethod.GET)
    public String hello(@RequestParam(value = "id", required = true) Integer id) {
        String name = getNameById(id);
        return (name == null) ? "Hello World" : ("Hello " + name);
    }

    public String getNameById(Integer id) {
        String sql = "select username from t_user where id = ? ";
        List<String> list = jdbcTemplate.queryForList(sql, new Object[] {id}, String.class);
        return list.isEmpty() ? null : list.get(0);
    }

}

訪問地址：http://localhost:8080/hello.do?id=1
結(jié)果輸出：Hello, ZhangSan