Jdbc-dbutils

1 brief introduction

DbUtils yes Apache The organization provides a solution to JDBC Open source tool class library for simple encapsulation , Using it can simplify JDBC Application development , At the same time, it will not affect the performance of the program . In brief, it is to simplify the database operation code in conjunction with the database connection pool , Database connection pooling simplifies connection operations , and DBUtils The operation of adding, deleting, modifying and querying is simplified , Bottom layer DbUtils Tool implementation , We just need to focus on usage and understand the implementation logic .

2 Common classes

DBUtils Tools
To make it easier to use JDBC,Apache The organization provides a tool class library commons-dbutils, It is a component that operates the database , Achieve a goal of JDBC Simple encapsulation , It can greatly simplify... Without affecting performance JDBC Ground coding workload .

API Introduce
commons-dbutils The core of is two classes org.apache.commons.DbUtils、org.apache.commons.dbutils.QueryRunner And an interface org.apache.commons.dbutils.ResultSetHealer.

DBUtils class
DBUtils Class is mainly used to close the connection 、 load JDBC Routine work such as drivers provides methods , The methods it provides are static methods .
1、close() Method
stay DBUtils Class , Provides three overloaded close() Method , These methods are used to close the data connection , And when the connection is closed , First, we will check whether the parameter is NULL, If not , The method will close Connection、Statement、ResultSet These three objects .
2、closeQuietly(Connection conn,Statement stmt,ResultSet rs) Method
This method is used to turn off Connection、Statement and ResultSet object . And close() Methods compared ,closeQuietly() Method can not only Connection、Statement and ResultSet The object is NULL Avoid closing if , You can also hide some of the things that are thrown out of the program SQL abnormal .
3、commitAndCloseQuietly(Connection conn) Method
commitAndCloseQuietly() Method to submit a connection , Then close the connection , And do not throw an exception when closing the connection .
4、loadDriver(java.lang.String driverClassName) Method
loadDriver() Method is used to load and register JDBC The driver , If you succeed, go back true. When this method is used , No need to capture ClassNotFoundException abnormal .

QueryRunner class
QueryRunner Class simplifies execution SQL Code for statement , It is associated with ResultSetHandler Together, you can complete most of the database operations , Greatly reduce the amount of coding .
QueryRunner Class provides two constructors , One is the default constructor , One is need javax.sql.DataSource As a construction method of parameters . So instead of providing a database connection for a method , Provided to the constructor DataSource Can be used to obtain a connection . however , In the use of JDBC When operating the database , Need to use Connection Object to operate on transactions ,QueryRunner Class provides different methods .

1、query(Connection conn,String sql,ResultSetHandler rsh,Object[] params) Method
This method is used to perform query operations , among , Parameters params Represents an array of objects , The value of each element in the array is used as the replacement parameter of the query statement . It should be noted that , This method automatically handles PreparedStatement and ResultSet Create and close .
It is worth mentioning that ,QueryRunner There is another method in query(Connection conn,String sql,Object[] params,ResultSetHandler rsh) The only difference between this method and the above method is the position of the parameter . But the variable parameter must be in the last item , So this method has expired .
2、query(String sql,ResultSetHandler rsh,Object[] params) Method
This method is used to perform query operations , Compared with the first method , It does not need to Connection Object passed to method , It can be from the data source provided to the constructor DataSource Or used setDataSource() Method .
3、query(Connection conn,String sql,ResultSetHandler rsh) Method
This method is used to execute a query result that does not require replacement parameters .
4、update(Connection conn,String sql,Object[] params) Method
This method is used to perform insertion 、 Update or delete , among , Parameters params Express SQL Substitution parameters in the statement .
5、update(Connection conn,String sql) Method
This method is used to perform insertion 、 Update or delete , It does not require substitution parameters .

ResultSetHandler Interface
ResultSetHandler The interface is used to handle ResultSet Result set , It can convert the data in the result set into different forms . Depending on the type of data in the result set ,ResultSetHandler Different implementation classes are provided .
1）AbstractKeyedHandler： This is an abstract class , It can convert the data in the result set into Map Storage .
2）AbstractListHandler： This is an abstract class , It can convert the data in the result set into List Storage .
3）ArrayHandler： Convert the first row of data in the result set to an object array .
4）ArrayListHandler： Turn each row of data in the result set into an object array , Then store the array in List in .
5）BaseResultSetHandler： An extension that converts the result set into other objects .
6）BeanHandler： Store the first row of data in the result set in a corresponding javaBean In the example .
7）BeanListHandler： Store each row of data in the result set in a corresponding javaBean In the example , then JavaBean The instance is stored in List in .
8）BeanMapHandler： Store each row of data in the result set in a corresponding javaBean In the example , Then according to the specified key Put each JavaBean Then store it in a Map in .
9）ColumnListHandler： Store the data of a column in the result set in List in
10）KeyedHandler： Encapsulate each row of data in the result set into a Map in , Then according to the specified key Put each JavaBean Then store it in a Map in .
11）MapHandler： Encapsulate the first row of data in the result set into a Map in ,key Is the column name ,value Is the corresponding value .
12）MapListHandler： Encapsulate each row of data in the result set into a Map in , Store it in List in .
13）ScalarHandler： Store the data in one column of a record in the result set as Object object .
in addition , stay ResultSetHandler Interface , Provides a separate method handle(java.sql.ResultSet rs), If the above implementation class does not provide the desired function , You can customize an implementation ResultSetHandler The class of the interface , And then by rewriting handle() Method , Realize the processing of result set .

3 rely on

        <dependency>
            <groupId>commons-dbutils</groupId>
            <artifactId>commons-dbutils</artifactId>
            <version>1.7</version>
        </dependency>
        <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>7.3.0</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.49</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.2.10</version>
        </dependency>

Tools

public class Dbutils {

    private DruidDataSource dataSource;

    @BeforeMethod
    public void testBefore() throws IOException, ClassNotFoundException, SQLException {
        /*Properties pros=new Properties();
        //properties.load(ClassLoader.getSystemClassLoader().getResourceAsStream("/jdbc.properties"));
        pros.load(Dbutils.class.getResourceAsStream("/jdbc.properties"));
        String user = pros.getProperty("user");
        String password = pros.getProperty("password");
        String url = pros.getProperty("url");
        String driverClass = pros.getProperty("driverClass");
        Class.forName(driverClass);
        Connection con = DriverManager.getConnection(url,user,password)*/

        Properties properties=new Properties();
        properties.load(Dbutils.class.getResourceAsStream("/jdbc.properties"));
        dataSource = new DruidDataSource();
        dataSource.configFromPropety(properties);
    }

    @Test
    public void test() throws SQLException {
        DruidPooledConnection dpc =  dataSource.getConnection();
        PreparedStatement preparedStatement=dpc.prepareStatement("show tables");
        ResultSet resultSet=preparedStatement.executeQuery();
        while(resultSet.next()) {
            System.out.println(resultSet.getString(1));
        }
    }
}

The configuration file

druid.name=myDruid
druid.url=jdbc:mysql://localhost:3306/dc?useUnicode=true&characterEncoding=UTF-8&useSSL=false&serverTimezone=GMT%2B8
druid.driverClassName=com.mysql.jdbc.Driver
druid.username=root
druid.password=root

4 DBUtils

DbUtils： Connect to database objects ----jdbc Collection class of auxiliary methods , Thread safety

4.1 Dbutils Introduction to three core functions

QueryRunner  Provided in pairs sql Statement operation API.
ResultSetHandler  Interface , Used for definition select After the operation , How to encapsulate result sets .
DbUtils  class , It's a tool class , Defines methods for closing resources and transactions 

4.2 QueryRunner

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Provide data sources : Use the connection object of the passed data source

Construction method
QueryRunner(DataSource) : Create core classes , And provide data source , Internal maintenance Connection
Common method

1 update(String sql , Object ... params):  perform DML sentence   Used to execute addition, deletion and modification statements 
2 query(String sql , ResultSetHandler , Object ... params) :  perform DQL sentence , And encapsulate the query results into objects . Used to execute query statements 
 No data source is provided :  You need to provide your own connection objects 
3.batch（）： Used to perform batch processing 

Construction method
QueryRunner() : Create core classes , No data source provided , When carrying out specific operations , It needs to be provided manually Connection
Common method
update(Connection conn , String sql , Object … params) : Use the Connection, complete
DML sentence
query(Connection conn , String sql , ResultSetHandler , Object … params) : Use the Connection, perform DQL sentence , And encapsulate the query results into objects .
QueryRunner Implementation add 、 to update 、 Delete operation
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update(String sql, Object… params) : Used to add table data 、 Delete 、 update operation
queryRunner.update(sql)： For increasing 、 Delete 、 modify
queryRunner.query(sql,rsh)： For queries

 @Test
    public void insert() throws Exception {
        //  Get a to execute SQL Statement object 
        QueryRunner qr = new QueryRunner(dataSource);
        String sql = "INSERT INTO stu(name, score) VALUES(?, ?)";
        Object[] params = {" Centenary mountain ", "50"};
        int count = qr.update(sql, params);
        System.out.println(" Successful implementation :=" + count);
    }
    
@Test
 public static void insert(){
        QueryRunner qr = new QueryRunner();
        String sql = "insert into student values(112,' Zhang San ',19)";
        Connection conn = null;
        try {
            conn = JDBCUtils.getConnection();
            int count = qr.update(conn,sql);
            System.out.println(count);
            DbUtils.closeQuietly(conn);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Test
    public void update() throws Exception {
        QueryRunner qr = new QueryRunner(dataSource);
        String sql = "UPDATE stu SET name=?,score=? WHERE id=?";
        Object[] params = {" Mango. 99", "99", 6};
        int count = qr.update(sql, params);
        System.out.println(count);
    }

@Test
   public static void update(){
        QueryRunner qr = new QueryRunner();
        String sql = "update student set sage= sage+10 where sno = 110";
        Connection conn = null;
        try {
            conn = JDBCUtils.getConnection();
            int count = qr.update(conn,sql);
            System.out.println(count);
            DbUtils.closeQuietly(conn);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
、
   @Test
    public void delete() throws SQLException {
        QueryRunner queryRunner = new QueryRunner(dataSource);
        String sql = "DELETE from stu WHERE id = ?";
        Object[] params = {6};
        int r = queryRunner.update(sql, params);
        System.out.println(r);
    }
@Test
  public static void delete(){
        QueryRunner qr = new QueryRunner();
        String sql = "delete from student where sno = 112";
        Connection conn = null;
        try {
            conn = JDBCUtils.getConnection();
            int count = qr.update(conn,sql);
            System.out.println(count);
            DbUtils.closeQuietly(conn);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

QueryRunner Implement query operation
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query(String sql, ResultSetHandler rsh, Object… params) Used to complete the query operation of table data
Parameters :
String sql: sql sentence , Parameter use ? replace
ResultSetHandler＜T＞ rsh: Result set processor , Interface , The implementation class object must be passed
Object … params: Variable parameters , Pass parameter list , Array .
effect : to sql in ? Assign a value .
ResultSetHandler Result set
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BeanHandler： Encapsulates the first record in the result set into a specified JavaBean in .
BeanListHandler： Encapsulate each record in the result set to the specified JavaBean in , Will these JavaBean After packaging to List Collection
ScalarHandler： It is used for single data . for example select count(*) from Table operations .
ColumnListHandler： Set the value of the specified column in the result set , Package into a List Collection
JavaBean
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JavaBean It's a class , It is often used to encapsulate data in development ,. Has the following characteristics .

Need to implement interface ：java.io.Serializable , Usually, the step of implementing the interface is omitted , Will not affect the program .
Provide private fields ：private type Field name ;
Provide getter/setter Method ：
Provide nonparametric construction
BeanHandler
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One of the ways to process the result set of query data table :
BeanHandler Processing mode The data in the first row of the result set of the data table , Encapsulated into JavaBean Class object
Construction method : BeanHandler(Class＜T＞ type) Pass a Class Type object , The object of which class the result is encapsulated

 @Test
    public void testQueryBeanHandler() throws Exception{
        QueryRunner queryRunner = new QueryRunner(dataSource);
        String sql = "SELECT * FROM stu WHERE id = ?";
        Object[] params = {5};
        //  Query and encapsulate 
        Stu pro = queryRunner.query(sql, new BeanHandler<>(Stu.class), params);
        System.out.println(pro);
    }

BeanListHandler
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One of the ways to process the result set of query data table :
BeanListHandler Processing mode The data in each row of the data table , Encapsulated into JavaBean Class object , Multiple lines of data , Multiple JavaBean object , Storage List aggregate .

   @Test
   public void testQueryBeanListHandler() throws Exception{
       QueryRunner queryRunner = new QueryRunner(DBCPUtil.getDataSource());
       String sql = "SELECT * FROM product";
       Object[] params = {};
       List<Product> pros = queryRunner.query(sql, new BeanListHandler<Product>(Product.class), params);
       for (Product pro : pros) {
           System.out.println(pro);
       }
   }

ScalarHander
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effect : Put a column of the query results , Store in List A collection of objects
Construction method :
public ScalarHandler(): Get the first column of the first row of the query result
public ScalarHandler(int index): Get the first row of query results index Column
public ScalarHandler(String ColumnName): Get the first row of the query result ColumnName Column

    @Test
    public void testQueryScalarHandler() throws Exception{
        QueryRunner queryRunner = new QueryRunner(DruidUtil.getDataSource());
        String sql = "SELECT * FROM product WHERE pid = ?";
        Object[] params = {2};
        //  Represents the second column of the second row of the query 
        Object o = queryRunner.query(sql, new ScalarHandler(2), params);
        System.out.println(o);
    }

ColumnListHandler
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Get the value of a column in the database , Usually used to summarize ; Commonly used in Aggregate functions

effect : Put a column of the query results , Store in List A collection of objects . be used for Aggregate functions
Construction method :
public ColumnListHandler(): Store the contents of the first column in List Collection
public ColumnListHandler(int index): Store the contents of the specified number column in List Collection
public ColumnListHandler(String ColumnName): Store the contents of the column corresponding to the specified column name in List Collection

    @Test
    public void testQueryColumnListHandler() throws Exception{
        QueryRunner queryRunner = new QueryRunner(C3P0Util.getDataSource());
        String sql = "SELECT * FROM product";
        // List<Object> list = queryRunner.query(sql, new ColumnListHandler());//  The default query is the first column 
        // List<Object> list = queryRunner.query(sql, new ColumnListHandler(2)); //  Query the second column specified by the relation table 
        List<Object> list = queryRunner.query(sql, new ColumnListHandler("pname"));
        for (Object o : list) {
            System.out.println(o);
        }
    }

2.ResultSetHandler Interface
1.ArrayHandler： The first row of data in the query result , Save to Object Array

    public static void arrayHandler(){
        QueryRunner qr = new QueryRunner();
        String sql = "select * from student";

        try {
            Connection conn = JDBCUtils.getConnection();
            Object[] query = qr.query(conn, sql, new ArrayHandler());
            for(Object obj : query)
                System.out.print(obj);
            DbUtils.closeQuietly(conn);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

2.arrayListHandler： The result of the query , Each line is first wrapped in Object Array , Then store the data in List aggregate

    public static void arrayListHandler(){
        QueryRunner qr = new QueryRunner();
        String sql = "select * from student";
        try {
            Connection conn = JDBCUtils.getConnection();
            List<Object[]> query = qr.query(conn, sql, new ArrayListHandler());
            for(Object[] objs : query){
                for (Object obj : objs){
                    System.out.print(obj+"  ");
                }
                System.out.println();
                DbUtils.closeQuietly(conn);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

3.BeanHandler： The first row of data in the query result , Package to student object

    public static void BeanHandler(){
        QueryRunner qr = new QueryRunner();
        String sql = "select * from student";
        try {
            Connection conn = JDBCUtils.getConnection();
            Student query = qr.query(conn, sql, new BeanHandler<Student>(Student.class));
            System.out.println(query);
            DbUtils.closeQuietly(conn);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

4.BeanLIstHandler： Encapsulate each row of the query result into student object , And then deposit List aggregate

    public static void BeanListHandler(){
        QueryRunner qr = new QueryRunner();
        String sql = "select * from student";
        try {
            Connection conn = JDBCUtils.getConnection();
            List<Student> query = qr.query(conn, sql, new BeanListHandler<Student>(Student.class));
            for (Student student : query){
                System.out.println(student+"  ");
            }
            DbUtils.closeQuietly(conn);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

5.ColumnListHandler： Encapsulate the data of the specified column of the query result into List Collection

    public static void ColumnListHandler(){
        QueryRunner qr = new QueryRunner();
        String sql = "select * from student";
        try {
            Connection conn = JDBCUtils.getConnection();
            List<Object> sno = qr.query(conn, sql, new ColumnListHandler<>("sno"));
            for (Object obj : sno)
                System.out.println(obj);
            DbUtils.closeQuietly(conn);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

6.ScalarHanlder： Put a column in the first row of the result set into an object

    public static void ScalarHandler(){
        QueryRunner qr = new QueryRunner();
        String sql = "select count(*) from student";
        try {
            Connection conn = JDBCUtils.getConnection();
            long query = qr.query(conn, sql, new ScalarHandler<Long>());
            System.out.println(query);
            DbUtils.closeQuietly(conn);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

7.MapHandler： Encapsulate the first row of data in the result set into a Map

    public static void MapHandler(){
        QueryRunner qr = new QueryRunner();
        String sql = "select * from student where sno = ?";
        try {
            Connection conn = JDBCUtils.getConnection();
            Map<String, Object> query = qr.query(conn, sql, new MapHandler(), 110);
            System.out.println(query);
            DbUtils.closeQuietly(conn);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

8.MapListHandler： Encapsulate each row of data in the result set into a Map in , Then store it in List

    public static void MapListHandler() {
        QueryRunner qr = new QueryRunner();
        String sql = "select * from student where sno = ?";
        try {
            Connection conn = JDBCUtils.getConnection();
            List<Map<String, Object>> query = qr.query(conn, sql, new MapListHandler(),110);
            for (Map<String, Object> map : query) {
                System.out.println(map);
            }
            DbUtils.closeQuietly(conn);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

KeyedHandler: Encapsulate each row of data in the result set into a Map in (List), And then put these map Save one more map
public static void KeyedHandler(){
QueryRunner queryRunner = new QueryRunner();
String sql = “select * from student”;
Map<String,Map<String,Object>>map = null;
try {
Connection conn = JDBCUtils.getConnection();
map = queryRunner.query(conn,sql,new KeyedHandler(“sname”));
for(Map.Entry<String,Map<String,Object>> entry : map.entrySet()){
System.out.println(entry.getKey());
System.out.println(entry.getValue());
}
DbUtils.closeQuietly(conn);
} catch (SQLException e) {
e.printStackTrace();
}
}

DBUtils class
It provides information about closing resources and transactions rollback,commit operation . The methods inside are static .

5 Summary

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DBUtils Tools

effect ： simplify JDBC The operation of
DBUtils Common classes and methods

QueryRunner Used to perform SQL Statement object

update(Connection conn, String sql, Object… params) Insert table record 、 Update table records 、 Delete table record
query(Connection conn, String sql, ResultSetHandler handler, Object… params) Query table record
ResultSetHandler The object that handles the result set

BeanHandler： Encapsulates the first record in the result set into a specified javaBean in .
BeanListHandler： Encapsulate each record in the result set to the specified javaBean in , Will these javaBean After packaging to List Collection
ScalarHandler： It is used for single data . for example select count(*) from Table operations .
ColumnListHandler： Sets the field value of the specified column in the result set to , Package into a List Collection

public class Dbutils {

    private static DruidDataSource dataSource;

    @BeforeMethod
    public void testBefore() throws IOException, ClassNotFoundException, SQLException {
        Properties properties=new Properties();
        properties.load(Dbutils.class.getResourceAsStream("/jdbc.properties"));
        dataSource = new DruidDataSource();
        dataSource.configFromPropety(properties);
    }

    @AllArgsConstructor
    private static class InitRunnable implements Runnable {
        private CountDownLatch countDownLatch;
        @SneakyThrows
        @Override
        public void run() {
            System.out.println(new Date());
            Dbutils.insert();
            countDownLatch.countDown();
        }
    }

    @Test
    public void curent() throws InterruptedException {
        CountDownLatch countDownLatch=new CountDownLatch(1000);
        List<Thread> workers = Stream
                .generate(() -> new Thread(new InitRunnable(countDownLatch)))
                .limit(1000)
                .collect(toList());
        workers.forEach(Thread::start);
        countDownLatch.await();
    }

    public static void insert() throws Exception {
        //  Get a to execute SQL Statement object 
        QueryRunner qr = new QueryRunner(dataSource);
        String sql = "INSERT INTO stu(name, score) VALUES(?, ?)";
        Object[] params = {" Centenary mountain ", "50"};
        int count = qr.update(sql, params);
    }
}