Spring JdbcTemplate: Three Ways to query (single value, single object, object collection)

Jdbctemplatedemo2.java

Package Helloworld.jdbctemplate;import Org.springframework.jdbc.core.jdbctemplate;import Java.sql.*;import java.util.list;/** * Function: query operation via JdbcTemplate * Query results need to be encapsulated (implement RowMapper interface) */public class JdbcTemplateDemo2 {//        JdbcTemplate Use steps://1, Import jar package, 2, set the database information, 3, set the data source, 4, call the method in the JdbcTemplate object to implement the operation public static void main (string[] args) {        Set database information and data source jdbctemplateobject Jdbctemplateobject = new Jdbctemplateobject (); JdbcTemplate JdbcTemplate = Jdbctemplateobject.getjdbctemplate ();//Insert Data//InsertData ();//query returns a value: Check        The total number of data in the table Queryforone (jdbctemplate);//Query returns Object queryForObject (JdbcTemplate);//query returns list collection    queryForList (JdbcTemplate);//use JDBC to implement query Querywithjdbc (); }//Insert data public static void InsertData () {Jdbctemplateobject jdbctemplateobject = new Jdbctemplateobject ()        ; JdbcTemplate JdbcTemplate = Jdbctemplateobject.getjdbctemplate ();//Call the method in the JdbcTemplate object to implement the Operation StrinG sql = "INSERT into user value (?,?,?)";        Table structure: ID (int, self-increment), name (varchar), age (int) int rows = jdbctemplate.update (sql, NULL, "Tom", 35);    System.out.println ("Number of inserted rows:" + rows);  /** * Query returns a value: Total number of data in query table */public static void Queryforone (JdbcTemplate jdbctemplate) {String sql =        "SELECT COUNT (*) from user";//Call method to get the number of records int count = Jdbctemplate.queryforobject (sql, Integer.class);    SYSTEM.OUT.PRINTLN ("Total data:" + count); }/** * Function: Query returns single Object * Step: New Myrowmapper class implement RowMapper interface, override Maprow method, specify return User Object */public static void Queryfo Robject (JdbcTemplate jdbctemplate) {String sql = "SELECT * from user where name =?"; /New Myrowmapper class implements the RowMapper interface, overriding the Maprow method, specifying the return user Object User user = Jdbctemplate.queryforobject (sql, new myrowma        Pper (), "Tom");    SYSTEM.OUT.PRINTLN (user); }/** * Function: Query return object collection * Step: New Myrowmapper class implement RowMapper interface, override Maprow method, specify return User Object */public static void QueryfoRList (JdbcTemplate jdbctemplate) {String sql = "SELECT * from user";//The third argument can be omitted list<user> us        ers = jdbctemplate.query (sql, New Myrowmapper ());    System.out.println (users);        }/** * uses the JDBC underlying implementation query */public static void Querywithjdbc () {Connection conn = null;        PreparedStatement psmt = null;        ResultSet rs = null;        String Jdbcurl = "Jdbc:mysql://192.168.184.130:3306/gxrdb"; try {//Load driver Class.forName ("Com.mysql.jdbc.Driver");//CREATE Connection conn = Drivermanag            Er.getconnection (Jdbcurl, "root", "root"); String sql = "SELECT * from user where name =?"; /precompiled SQL PSMT = conn.preparestatement (sql);//starting from 1, there is no need to psmt.setstring (1, "T Om ");//Execute SQL RS = Psmt.executequery ();//int num = Psmt.executeupdate (); Delete and change, return the operation record number//traverse result set while (Rs.next ()) {/////query the corresponding column nameValue, or it can be the position ordinal String name = rs.getstring ("name");                String age = rs.getstring ("Age");                SYSTEM.OUT.PRINTLN (name);            System.out.println (age);        }} catch (Exception e) {e.printstacktrace ();                } finally {try {rs.close ();                Psmt.close ();            Conn.close ();            } catch (SQLException e) {e.printstacktrace (); }        }    }}

Myrowmapper.java

Package Helloworld.jdbctemplate;import Org.springframework.jdbc.core.rowmapper;import Java.sql.ResultSet;import java.sql.sqlexception;/** * Implement RowMapper interface, return User Object * */public class Myrowmapper implements rowmapper<user>{    @Override public    User maprow (ResultSet ResultSet, int i) throws SQLException {//        get data in result set        String name = ResU Ltset.getstring ("name");        String age = resultset.getstring ("Age");//        encapsulates the data into a user object        user user = new user ();        User.setname (name);        User.setage (age);        return user;    }}

Jdbctemplateobject.java

 Packagehelloworld.jdbctemplate;Importorg.springframework.jdbc.core.JdbcTemplate;ImportOrg.springframework.jdbc.datasource.DriverManagerDataSource;/*** Function: Set the database information and data source * * Jdbctemplat use * 1, import jar package, 2, set database information, 3, set data source, 4, call method in JdbcTemplate object to implement Operation*/ Public classJdbctemplateobject {Drivermanagerdatasource dataSource;    JdbcTemplate JdbcTemplate;  PublicJdbctemplateobject () {//Setting Up Database information         This. DataSource =NewDrivermanagerdatasource ();  This. Datasource.setdriverclassname ("Com.mysql.jdbc.Driver");  This. Datasource.seturl ("Jdbc:mysql://192.168.184.130:3306/gxrdb");  This. datasource.setusername ("root");  This. Datasource.setpassword ("root");//set up a data source         This. JdbcTemplate =NewJdbcTemplate (DataSource); }     PublicDrivermanagerdatasource Getdatasource () {returnDataSource; }     Public voidSetdatasource (Drivermanagerdatasource dataSource) { This. DataSource =DataSource; }     PublicJdbcTemplate getjdbctemplate () {returnJdbcTemplate; }     Public voidsetjdbctemplate (JdbcTemplate jdbctemplate) { This. JdbcTemplate =JdbcTemplate; }}

User.java

 Packagehelloworld.jdbctemplate;/*** Data Encapsulation class **/ Public classUser {PrivateString name; PrivateString age;  PublicString GetName () {returnname; }     Public voidsetName (String name) { This. Name =name; }     PublicString getage () {returnAge ; }     Public voidsetage (String age) { This. Age =Age ; } @Override PublicString toString () {return"user{Name:" + name + "; Age: "+ Ages +"} "; }}

Spring JdbcTemplate: Three Ways to query (single value, single object, object collection)