概述
Sqlite
sqlite是C实现的一个开源SQL引擎,其api提供sql语法支持,通过sql解析后对存储层的磁盘文件进行操作,完整配置的sqlite库小于400kb,多用于移动端应用,小型项目中。
对Sqlite有兴趣的可以了解下其体系结构
之前自研SQL解析器的时候便是借鉴了SQLcompiler的源码,这里不展开介绍
封装Java的Sqlite连接池
首先maven项目引入依赖sqlite-jdbc,其主要是java版的sqliteapi,关于Sqlite api的操作,大家可以看菜鸟教程
<dependency> <groupId>org.xerial</groupId> <artifactId>sqlite-jdbc</artifactId> <version>3.30.1</version> </dependency>
同时引入spring jdbc方便解析数据
<dependency> <groupId>org.springframework</groupId> <artifactId>spring-jdbc</artifactId> <version>5.3.12</version> </dependency>
先编写测试用例
import org.junit.Test; import org.springframework.jdbc.core.RowMapper; import java.sql.ResultSet; import java.sql.SQLException; import java.util.LinkedList; import java.util.List; public class TestSqliteHelper { @Test public void test() throws SQLException, ClassNotFoundException { SqliteHelper sqliteHelper = SqliteHelper.GetSqliteHelper("test.db"); String sql = "CREATE TABLE COMPANY " + "(ID INT PRIMARY KEY NOT NULL," + " NAME TEXT NOT NULL, " + " AGE INT NOT NULL, " + " ADDRESS CHAR(50), " + " SALARY REAL)"; sqliteHelper.ExecuteUpdate(sql); sql = "INSERT INTO COMPANY (ID,NAME,AGE,ADDRESS,SALARY) " + "VALUES (1, 'Paul', 32, 'California', 20000.00 );"; sqliteHelper.ExecuteUpdate(sql); sql = "SELECT * FROM COMPANY;"; List<String> datas = new LinkedList<>(); datas = sqliteHelper.ExecuteQuery(sql, new RowMapper<String>() { @Override public String mapRow(ResultSet rs, int index) throws SQLException { return rs.getString("NAME"); } } ); sqliteHelper.PutSqliteHelper(); } }
再根据TDD实现ExecuteUpdateGetSqliteHelper、ExecuteQuery、PutSqliteHelper等方法
import org.springframework.jdbc.core.RowMapper; import java.sql.*; import java.util.ArrayList; import java.util.HashMap; import java.util.LinkedList; import java.util.List; import java.util.concurrent.locks.ReentrantLock; public class SqliteHelper { /** * 磁盘文件名 即db */ private String path = null; /** * 操作链接 */ private Connection connection = null; /** * 语法执行层 */ private Statement statement = null; /** * 构建一次链接 * * @param path * @throws SQLException * @throws ClassNotFoundException */ SqliteHelper(String path) throws SQLException, ClassNotFoundException { this.path = path; this.connection = this.getConnect(path); } /** * 读写锁,也可以使用ConcurrentHashMap */ static ReentrantLock hashMapLock = new ReentrantLock(); /** * Sqlite的连接池 */ static HashMap<String, List<SqliteHelper>> sqlitePool = new HashMap<>(); /** * sqlite对磁盘文件的操作是在一次连接上执行 * * @param path sqlite数据存储的磁盘文件 * @return */ public static SqliteHelper GetSqliteHelper(String path) throws SQLException, ClassNotFoundException { hashMapLock.lock(); List<SqliteHelper> sqliteHelpers = sqlitePool.get(path); if (sqliteHelpers == null) { sqliteHelpers = new LinkedList<>(); sqlitePool.put(path, sqliteHelpers); } SqliteHelper sqliteHelper = new SqliteHelper(path); sqliteHelpers.add(sqliteHelper); return sqliteHelper; } public void PutSqliteHelper() throws SQLException { hashMapLock.lock(); List<SqliteHelper> sqliteHelpers = sqlitePool.get(this.path); if (sqliteHelpers == null) { sqliteHelpers = new LinkedList<>(); sqlitePool.put(path, sqliteHelpers); } if(sqliteHelpers.size() > 2){ releaseConn(); }else{ sqliteHelpers.add(this); } } /** * 获取Sqlite操作链接 * * @param path sqlite数据表,为磁盘文件名 * @return */ private Connection getConnect(String path) throws ClassNotFoundException, SQLException { Connection c = null; Class.forName("org.sqlite.JDBC"); c = DriverManager.getConnection("jdbc:sqlite:" + path); return c; } /** * @param sql 执行的sqlite 语句 * @param row * @param <T> 映射的模板 * @return */ public <T> List<T> ExecuteQuery(String sql, RowMapper<T> row) throws SQLException { try { List<T> datas = new ArrayList<>(); ResultSet resultSet = getStmt().executeQuery(sql); while (resultSet.next()) { datas.add(row.mapRow(resultSet, resultSet.getRow())); } resultSet.close(); return datas; } finally { releaseConn(); } } public void ExecuteUpdate(String sql) throws SQLException { getStmt().executeUpdate(sql); } private Statement getStmt() throws SQLException { if (this.statement == null) { this.statement = this.connection.createStatement(); } return this.statement; } private void releaseConn() throws SQLException { if (this.connection != null) { this.connection.close(); this.connection = null; } if (this.statement != null) { this.statement.close(); this.statement = null; } } }
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