摘要：連接池的名稱指定由連接池所創(chuàng)建的連接的自動(dòng)提交狀態(tài)。由連接池所創(chuàng)建的連接對(duì)數(shù)據(jù)庫(kù)的只讀屬性指定由連接池所創(chuàng)建的連接的事務(wù)級(jí)別。以毫秒表示的當(dāng)連接池中沒有可用連接時(shí)等待可用連接返回的時(shí)間，超時(shí)則拋出異常，值為時(shí)無(wú)限期等待。

什么是 Connection Pool -- 連接池呢？

我就不解釋了。不太清楚的看這篇文章 [生產(chǎn)級(jí)別Nodejs開發(fā)實(shí)踐-使用連接池]（這篇文章的前半部分講述了什么是連接池）

它的英文文檔在：[The Tomcat JDBC Connection Pool]

Tomcat 不僅是非常受歡迎的 Servlet 容器，也是同時(shí)為我們提供了很多非常實(shí)用組件。 jdbc pool 就是其中一個(gè)非常實(shí)用且高效的 jdbc 連接池的實(shí)現(xiàn). Tomcat 官方大概列出了15條tomcat相對(duì)于其他連接池的優(yōu)點(diǎn)，我這里就不在詳細(xì)解釋了。

jdbc pool 組件存在于 tomcat8 release 版本的 lib/tomcat-jdbc.jar 包中。

我們所使用的到所有類都存在于 org.apache.tomcat.jdbc.pool 包名下。

這里面我們以 mysql 作為數(shù)據(jù)庫(kù)來(lái)演示
添加 mysql-connector 依賴

xml
    mysql
    mysql-connector-java
    5.1.34

xml
    org.apache.tomcat
    tomcat-jdbc
    8.0.15

javaimport java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.apache.tomcat.jdbc.pool.DataSource;
import org.apache.tomcat.jdbc.pool.PoolProperties;

// main
// 創(chuàng)建連接池屬性對(duì)象
PoolProperties poolProps = new PoolProperties();
poolProps.setUrl("jdbc:mysql://localhost:3306/test");

poolProps.setDriverClassName("com.mysql.jdbc.Driver");

poolProps.setUsername("root");

poolProps.setPassword("123456");

// 創(chuàng)建連接池, 使用了 tomcat 提供的的實(shí)現(xiàn)，它實(shí)現(xiàn)了 javax.sql.DataSource 接口
DataSource dataSource = new DataSource();
// 為連接池設(shè)置屬性
dataSource.setPoolProperties(poolProps);

try (Connection conn = dataSource.getConnection()) {

    PreparedStatement state = conn.prepareStatement("select * from book");

    ResultSet result = state.executeQuery();

    StringBuilder stringBuilder = new StringBuilder();

    while ( result.next() ) {
            stringBuilder.append("[ id: "+ result.getInt("id") + ", ").append("name: " + result.getString("name") + ",	").append("publisher: " + result.getString("publisher")).append(" ]
");
    }

    System.out.println(stringBuilder.toString());

} 
catch (SQLException e) 
{
    e.printStackTrace();
}

java    private volatile Properties dbProperties = new Properties();
    private volatile String url = null;
    private volatile String driverClassName = null;
    private volatile Boolean defaultAutoCommit = null;
    private volatile Boolean defaultReadOnly = null;
    private volatile int defaultTransactionIsolation = DataSourceFactory.UNKNOWN_TRANSACTIONISOLATION;
    private volatile String defaultCatalog = null;
    private volatile String connectionProperties;
    private volatile int initialSize = 10;
    private volatile int maxActive = DEFAULT_MAX_ACTIVE;
    private volatile int maxIdle = maxActive;
    private volatile int minIdle = initialSize;
    private volatile int maxWait = 30000;
    private volatile String validationQuery;
    private volatile int validationQueryTimeout = -1;
    private volatile String validatorClassName;
    private volatile Validator validator;
    private volatile boolean testOnBorrow = false;
    private volatile boolean testOnReturn = false;
    private volatile boolean testWhileIdle = false;
    private volatile int timeBetweenEvictionRunsMillis = 5000;
    private volatile int numTestsPerEvictionRun;
    private volatile int minEvictableIdleTimeMillis = 60000;
    private volatile boolean accessToUnderlyingConnectionAllowed = true;
    private volatile boolean removeAbandoned = false;
    private volatile int removeAbandonedTimeout = 60;
    private volatile boolean logAbandoned = false;
    private volatile String name = "Tomcat Connection Pool["+(poolCounter.addAndGet(1))+"-"+System.identityHashCode(PoolProperties.class)+"]";
    private volatile String password;
    private volatile String username;
    private volatile long validationInterval = 30000;
    private volatile boolean jmxEnabled = true;
    private volatile String initSQL;
    private volatile boolean testOnConnect =false;
    private volatile String jdbcInterceptors=null;
    private volatile boolean fairQueue = true;
    private volatile boolean useEquals = true;
    private volatile int abandonWhenPercentageFull = 0;
    private volatile long maxAge = 0;
    private volatile boolean useLock = false;
    private volatile InterceptorDefinition[] interceptors = null;
    private volatile int suspectTimeout = 0;
    private volatile Object dataSource = null;
    private volatile String dataSourceJNDI = null;
    private volatile boolean alternateUsernameAllowed = false;
    private volatile boolean commitOnReturn = false;
    private volatile boolean rollbackOnReturn = false;
    private volatile boolean useDisposableConnectionFacade = true;
    private volatile boolean logValidationErrors = false;
    private volatile boolean propagateInterruptState = false;
    private volatile boolean ignoreExceptionOnPreLoad = false;

javapoolProps.setJdbcInterceptors("org.apache.tomcat.jdbc.pool.interceptor.ConnectionState;org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer");