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Detailed use of dbutils ＃ yyds dry goods inventory ＃

2022-07-06 02:48:00 【Liang Yunliang】

DBUtils

brief introduction

DBUtils yes Java Database operation utility in programming , Small, simple and practical .DBUtils Encapsulates the JDBC The operation of , To simplify the JDBC operation , Can reduce the 60% Code above .

DBUtils Introduction to three core functions

QueryRunner： Core classes provide access to sql Statement operation API
- QueryRunner(DataSourcr ds)： Provide data sources （ Connection pool ）,DbUtils Bottom layer automatic maintenance connection connection
- update(String sql,Obj…params)： Perform an update operation
- query(String sql,ResultSetHandler<T>rsh,Object…panrams)： Perform query operation
ResultSetHandler： Result set processing class , Used for definition select After the operation , How to encapsulate result sets
- ArrayHandler： Put the first row of data in the query result set into an array . Suitable for 1 Bar record .
- ArrayListHandler： Put each row of data in the query result into an array , Then put the array into the collection List in . It is suitable for taking multiple records .
- BeanHandler： Encapsulate the first row of data in the result set into a corresponding JavaBean In the example
- BeanListHandler： Encapsulate each row of data in the result set into a corresponding JavaBean In the example , Then store these objects in List in .
- 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 .
- MapListHandler： Save each row of the query result into a map in , Key is column name , The value is the value of each column ; And then map Deposit in list in
- ColumnListHandler： Store the data of a column in the result set in List in .
- KeyedHandler(name)： Encapsulate each row of data in the result set into a Map in (List<Map>), And then put these map Save one more map in , Its key For the specified column .
- ScalarHandler: Put a column in the first row of the result set into an object .// a key
DBUtils： Tool class , Defines methods for closing resources and transactions .

Example ： use Druid and dbutils Realize to Dept Of CRUD

First step ：Dept.java：<a rel=“nofollow” href=“ https://blog.csdn.net/lianghecai52171314/article/details/101469279”>Dept Source code </a>

The second step ： New projects , Join in Maven rely on ：

<dependency>
  <groupId>commons-dbutils</groupId>
  <artifactId>commons-dbutils</artifactId>
  <version>1.7</version>
</dependency>
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>druid</artifactId>
    <version>1.1.17</version>
</dependency>

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The second step ： stay resources Create under directory mysql.properties, The code is as follows ：

driverClassName=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/test?useSSL=false&serverTimezone=UTC&user=root&password=&useUnicode=true&characterEncoding=UTF8&autoReconnect=true&failOverReadOnly=false
username=root
password=root


filters=stat
initialSize=2
maxActive=300
maxWait=60000
timeBetweenEvictionRunsMillis=60000
minEvictableIdleTimeMillis=300000
validationQuery=SELECT 1
testWhileIdle=true
testOnBorrow=false
testOnReturn=false
poolPreparedStatements=false
maxPoolPreparedStatementPerConnectionSize=200

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The third step ： Create a database connection tool class ：

public class DBUtil {
    private static final ThreadLocal<Connection> threadLocal = new ThreadLocal<>();
    private static DataSource dataSource = null;

    private DBUtil() {
    }

    static {    // Profile loading , Only once 
        try (InputStream is = DBUtil.class.getResourceAsStream("/mysql.properties");) {
            Properties properties = new Properties();
            properties.load(is);
            dataSource = DruidDataSourceFactory.createDataSource(properties);
        } catch (Exception e1) {
            throw new RuntimeException(" Exception reading configuration file ", e1);
        }
    }

    public static Connection getConnection() {    // Get the connection 
        Connection conn = null;
        try {
            conn = threadLocal.get();   // Get from current thread  conn
            if (conn == null || conn.isClosed()) {
                conn = dataSource.getConnection();
                threadLocal.set(conn);
            }
        } catch (Exception e) {
            throw new RuntimeException(" Connection database exception ", e);
        }
        return conn;
    }

    public static QueryRunner getQueryRunner() {
        return new QueryRunner(dataSource);
    }

    public static void release(Connection conn) {
        try { //  This form is recommended to release resources , because finally The inside will be released 
            if (conn != null) {
                conn.close();
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

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Step four ： Test transactions

public static void main(String[] args) {
    Connection conn = getConnection();
    try {
        conn.setAutoCommit(false); //  Set transaction commit to manual 
        String sql = "insert into tb_dept (dname,loc) values(?,?)";
        QueryRunner queryRunner = getQueryRunner();
        queryRunner.update(conn, sql, "aa", "aaaaa");
        System.out.println(3 / 0);
        queryRunner.update(sql, "bb", "bbbbbbbbbb");
        conn.commit();
    } catch (SQLException e) {
        e.printStackTrace();
        try {
            conn.rollback();
        } catch (SQLException ex) {
            ex.printStackTrace();
        }
    } finally {
        release(conn);
    }
}

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Step five ：DeptDaoImpl.java

public class DeptDaoImpl {
    private QueryRunner queryRunner = DBUtil.getQueryRunner();

    public int insertDept(Dept dept) throws SQLException {
        String sql = "insert into tb_dept (deptno, dname, loc) values (?, ?, ?)";
        return queryRunner.update(sql, dept.getDeptno(), dept.getDname(), dept.getLoc());
    }

    public int batchInsertDept(List<Dept> deptList) throws SQLException {
        Object[][] params = new Object[deptList.size()][3];

        for (int i = 0; i < params.length; i++) {
            Dept dept = deptList.get(i);
            params[i][0] = dept.getDeptno();
            params[i][1] = dept.getDname();
            params[i][2] = dept.getLoc();
        }

        StringBuilder wenHao = new StringBuilder();
        for (int i = 0; i < params[0].length; i++) {
            wenHao.append("?,");
        }
        String sql = "insert into tb_dept values(" + wenHao.deleteCharAt(wenHao.length() - 1) + ")";

        queryRunner.batch(sql, params);
        return 1;  //  If you don't throw an exception , Just go back to 1, Indicates that the deletion was successful 
    }

    public int deleteDeptByDeptno(Byte deptno) throws SQLException {
        String sql = "delete from tb_dept where deptno = ?";
        return queryRunner.update(sql, deptno);
    }

    public int deleteDeptByCondition(Dept dept) throws SQLException {
        List<Object> paramValueList = new ArrayList<>();
        StringBuffer paramBuf = new StringBuffer("1=1 ");

        if (dept.getDeptno() != null) {
            paramBuf.append("and deptno= ? ");
            paramValueList.add(dept.getDeptno());
        }
        if (dept.getDname() != null) {
            paramBuf.append("and dname= ? ");
            paramValueList.add(dept.getDname());
        }
        if (dept.getLoc() != null) {
            paramBuf.append("and loc= ? ");
            paramValueList.add(dept.getLoc());
        }

        String sql = "delete from tb_dept where " + paramBuf.substring(0, paramBuf.length() - 3);
        return queryRunner.update(sql, paramValueList.toArray());
    }

    public int batchDeleteDeptByDeptnos(String deptnos) throws SQLException {
        String[] split = deptnos.split(",");
        Object[][] params = new Object[1][];

        StringBuilder wenHao = new StringBuilder();
        for (int i = 0; i < split.length; i++) {
            wenHao.append("?,");
        }
        params[0] = split;

        String sql = "delete from tb_dept where deptno in (" + wenHao.deleteCharAt(wenHao.length() - 1) + ")";

        queryRunner.batch(sql, params);
        return 1;  //  If you don't throw an exception , Just go back to 1, Indicates that the deletion was successful 
    }

    public int updateDept(Dept dept) throws SQLException {
        String sql = "update tb_dept set dname= ? ,loc= ? where deptno = ?";
        return queryRunner.update(sql, dept.getDname(), dept.getLoc(), dept.getDeptno());
    }

    public long selectCount() throws SQLException {
        String sql = "select count(*) from tb_dept";
        // ScalarHandler： Put a column in the first row of the query result into an object ; Pinpoint to a value 
        Long query = queryRunner.query(sql, new ScalarHandler<Long>());
        return query.intValue();
    }

    public long selectCountByCondition(Dept dept) throws SQLException {
        List<Object> paramValueList = new ArrayList<>();
        StringBuffer paramBuf = new StringBuffer("1=1 ");

        if (dept.getDeptno() != null) {
            paramBuf.append("and deptno= ? ");
            paramValueList.add(dept.getDeptno());
        }
        if (dept.getDname() != null) {
            paramBuf.append("and dname= ? ");
            paramValueList.add(dept.getDname());
        }
        if (dept.getLoc() != null) {
            paramBuf.append("and loc= ? ");
            paramValueList.add(dept.getLoc());
        }

        String sql = "select count(*) from tb_dept where " + paramBuf.substring(0, paramBuf.length() - 3);
        Long query = queryRunner.query(sql, new ScalarHandler<Long>(), paramValueList.toArray());
        return query.intValue();
    }

    public Dept selectDeptByDeptno(Byte deptno) throws SQLException {
        String sql = "select deptno as deptno, dname as dname, loc as loc from tb_dept where deptno = ?";
        return queryRunner.query(sql, new BeanHandler<>(Dept.class), deptno);
    }

    public List<Dept> selectAllDept() throws SQLException {
        String sql = "select deptno as deptno, dname as dname, loc as loc from tb_dept";
        return queryRunner.query(sql, new BeanListHandler<>(Dept.class));
    }

    public List<Dept> selectDeptByCondition(Dept dept) throws SQLException {
        List<Object> paramValueList = new ArrayList<>();
        StringBuffer paramBuf = new StringBuffer("1=1 ");

        if (dept.getDeptno() != null) {
            paramBuf.append("and deptno= ? ");
            paramValueList.add(dept.getDeptno());
        }
        if (dept.getDname() != null) {
            paramBuf.append("and dname= ? ");
            paramValueList.add(dept.getDname());
        }
        if (dept.getLoc() != null) {
            paramBuf.append("and loc= ? ");
            paramValueList.add(dept.getLoc());
        }

        String sql = "select deptno as deptno, dname as dname, loc as loc from tb_dept where " + paramBuf.substring(0, paramBuf.length() - 3);
        return queryRunner.query(sql, new BeanListHandler<>(Dept.class), paramValueList.toArray());
    }

    public List<Dept> selectDeptWithPagination(int page, int rows) throws SQLException {
        String sql = "select deptno as deptno, dname as dname, loc as loc from tb_dept limit ?, ?";
        return queryRunner.query(sql, new BeanListHandler<>(Dept.class), (page - 1) * rows, rows);
    }

    public List<Dept> selectDeptWithPaginationByCondition(int page, int rows, Dept dept) throws SQLException {
        List<Object> paramValueList = new ArrayList<>();
        StringBuffer paramBuf = new StringBuffer("1=1 ");

        if (dept.getDeptno() != null) {
            paramBuf.append("and deptno= ? ");
            paramValueList.add(dept.getDeptno());
        }
        if (dept.getDname() != null) {
            paramBuf.append("and dname= ? ");
            paramValueList.add(dept.getDname());
        }
        if (dept.getLoc() != null) {
            paramBuf.append("and loc= ? ");
            paramValueList.add(dept.getLoc());
        }

        String sql = "select deptno as deptno, dname as dname, loc as loc from tb_dept where " + paramBuf.substring(0, paramBuf.length() - 3) + " limit ?, ?";

        paramValueList.add((page - 1) * rows);
        paramValueList.add(rows);
        return queryRunner.query(sql, new BeanListHandler<>(Dept.class), paramValueList.toArray());
    }
}

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dynamic SQL And static SQL

SQL Statements can be divided into static statements from the perspective of compilation and operation SQL and dynamic SQL, So-called SQL The dynamic and static state of , Refer to SQL When statements are compiled and executed .

These two kinds of SQL In the way of use 、 Operation mechanism and performance have their own characteristics :

static state SQL： static state SQL Statements are generally used in embedded systems SQL Application , Before the program runs ,SQL Statements must be certain when programming , for example SQL The column and table names involved in the statement must exist . static state SQL Statement is compiled before the application runs , The compiled results are stored in the database . Then the program runs , The database will directly execute the compiled SQL sentence , Reduce runtime overhead .
dynamic SQL： dynamic SQL Statements are compiled and executed while the application is running , for example , Use DB2 Interactive tools for CLP When accessing the database , User entered SQL The statement is indeterminate , therefore SQL Statements can only be compiled dynamically . dynamic SQL More applications , common CLI and JDBC Applications use dynamic SQL.

static state sql The access path of is determined before running , And dynamic sql The access path is dynamically generated at run time .

Be careful ： stay SQL If some parameters are not determined , Such as "select * from t1 where c1>? and c2<?", This statement is static SQL, Not dynamic SQL, Although the value of individual parameters is not known , But the whole SQL The structure of has been determined , The database can be compiled , In the execution phase, you only need to add the values of individual parameters .

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