implementation "org.springframework.boot:spring-boot-starter-web:2.4.9"

implementation "mysql:mysql-connector-java:8.0.26"

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/test?characterEncoding=utf-8&useSSL=false
    username: root
    password: 123456
    driver: com.mysql.cj.jdbc.Driver

-- create table `account`
# DROP TABLE `account` IF EXISTS
CREATE TABLE `account` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) NOT NULL,
  `money` double DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
INSERT INTO `account` VALUES ('1', 'aaa', '1000');
INSERT INTO `account` VALUES ('2', 'bbb', '1000');
INSERT INTO `account` VALUES ('3', 'ccc', '1000');

data class Account (
    var id:Int = 0,
    var name: String? = null,
    var money :Double= 0.0
)

@Mapperpublic interface AccountMapper {

    @Insert("insert into account(name, money) values(#{name}, #{money})")
    int add(@Param("name") String name, @Param("money") double money);

    @Update("update account set name = #{name}, money = #{money} where id = #{id}")
    int update(@Param("name") String name, @Param("money") double money, @Param("id") int  id);

    @Delete("delete from account where id = #{id}")
    int delete(int id);

    @Select("select id, name as name, money as money from account where id = #{id}")
    Account findAccount(@Param("id") int id);

    @Select("select id, name as name, money as money from account")
    List<Account> findAccountList();}

@Mapper
interface AccountMapper {
    @Insert("insert into account(name, money) values(#{name}, #{money})")
    fun add(@Param("name") name: String?, @Param("money") money: Double): Int

    @Update("update account set name = #{name}, money = #{money} where id = #{id}")
    fun update(
        @Param("name") name: String?,
        @Param("money") money: Double,
        @Param("id") id: Int
    ): Int

    @Delete("delete from account where id = #{id}")
    fun delete(id: Int): Int

    @Select("select id, name as name, money as money from account where id = #{id}")
    fun findAccount(@Param("id") id: Int): Account?

    @Select("select id, name as name, money as money from account")
    fun findAccountList(): List<Account?>?
}

@CrossOrigin
@RestController
class MainControl {
    

    @Autowired
    lateinit var accountService: AccountService


    @GetMapping(value = ["/list"])
    fun getAccounts(): List<Account> {
        return accountService.findAccountList()
    }

    @GetMapping(value = ["/{id}"])
    fun getAccountById(@PathVariable("id") id: Int): Account? {
        return accountService.findAccount(id)
    }

    @PutMapping(value = ["/{id}"])
    fun updateAccount(
        @PathVariable("id") id: Int, @RequestParam(value = "name", required = true) name: String?,
        @RequestParam(value = "money", required = true) money: Double
    ): String {
        val t = accountService.update(name, money, id)
        return if (t == 1) {
            "success"
        } else {
            "fail"
        }
    }

    @DeleteMapping(value = ["/{id}"])
    fun delete(@PathVariable(value = "id") id: Int): String {
        val t = accountService.delete(id)
        return if (t == 1) {
            "success"
        } else {
            "fail"
        }
    }
}

ALTER TABLE tableName ADD COLUMN columnName VARCHAR(20) DEFAULT NULL --增加一个字段，默认为空
ALTER TABLE tableName ADD COLUMN columnName VARCHAR(20) NOT NULL     --增加一个字段，默认不能为空

ALTER TABLE tableName DROP COLUMN columnName --删除一个字段

ALTER TABLE tableName MODIFY COLUMN columnName VARCHAR(10) --修改一个字段的类型

Declare @Pk varChar(100);
Select @Pk=Name from sysobjects where Parent_Obj=OBJECT_ID('tableName') and xtype='PK';
if @Pk is not null
exec('Alter table tableName Drop '+ @Pk)

alter table 表名 add unique(字段名);

//demo1.js
export const str = 'hello world'

export function f(a){
    return a+1
}

//demo2.js
import { str, f } from 'demo1'

//demo1.js
export default {
    a: 'hello',
    b: 'world'      
}

//demo2.js
import obj from 'demo1'

_MyHomePageState createState() => _MyHomePageState();

_MyHomePageState createState(){ 
	return  _MyHomePageState();
}

public enum ColorEnum {  
  RED, GREEN, BLANK, YELLOW  
} 
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enum ColorEnum {
    GREEN, YELLOW, RED
}
public class ColorTest {
    ColorEnum color = ColorEnum.RED;

    public void change() {
        switch (color) {
            case RED:
                color = ColorEnum.GREEN;
                break;
            case YELLOW:
                color = ColorEnum.RED;
                break;
            case GREEN:
                color = ColorEnum.YELLOW;
                break;
        }
    }
}
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public class EnumTest {
    public static void main(String[] args) {
        ErrorCodeEnum errorCode = ErrorCodeEnum.SUCCESS;
        System.out.println("状态码：" + errorCode.code() + 
                           " 状态信息：" + errorCode.msg());
    }
}

enum ErrorCodeEnum {
    SUCCESS(1000, "success"),
    PARAM_ERROR(1001, "parameter error"),
    SYS_ERROR(1003, "system error"),
    NAMESPACE_NOT_FOUND(2001, "namespace not found"),
    NODE_NOT_EXIST(3002, "node not exist"),
    NODE_ALREADY_EXIST(3003, "node already exist"),
    UNKNOWN_ERROR(9999, "unknown error");

    private int code;
    private String msg;

    ErrorCodeEnum(int code, String msg) {
        this.code = code;
        this.msg = msg;
    }

    public int code() {
        return code;
    }

    public String msg() {
        return msg;
    }

    public static ErrorCodeEnum getErrorCode(int code) {
        for (ErrorCodeEnum it : ErrorCodeEnum.values()) {
            if (it.code() == code) {
                return it;
            }
        }
        return UNKNOWN_ERROR;
    }
}
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public class EnumTest {
    public static void main(String[] args) {
        ColorEnum colorEnum = ColorEnum.RED;
        System.out.println(colorEnum.toString());
    }
}

enum ColorEnum {
    RED("红色", 1), GREEN("绿色", 2), BLANK("白色", 3), YELLOW("黄色", 4);
    //  成员变量
    private String name;
    private int index;

    //  构造方法
    private ColorEnum(String name, int index) {
        this.name = name;
        this.index = index;
    }

    //覆盖方法
    @Override
    public String toString() {
        return this.index + "：" + this.name;
    }
}
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public class EnumTest {
    public static void main(String[] args) {
        ColorEnum colorEnum = ColorEnum.RED;
        colorEnum.print();
        System.out.println("颜色：" + colorEnum.getInfo());
    }
}

interface Behaviour {
    void print();

    String getInfo();
}

enum ColorEnum implements Behaviour {
    RED("红色", 1), GREEN("绿色", 2), BLANK("白色", 3), YELLOW("黄色", 4);
    private String name;
    private int index;

    private ColorEnum(String name, int index) {
        this.name = name;
        this.index = index;
    }

    @Override
    public void print() {
        System.out.println(this.index + "：" + this.name);
    }

    @Override
    public String getInfo() {
        return this.name;
    }
}
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public class EnumTest {
    public static void main(String[] args) {
        // 赋值第一个枚举类
        ColorInterface colorEnum = ColorInterface.ColorEnum.RED;
        System.out.println(colorEnum);
        // 赋值第二个枚举类
        colorEnum = ColorInterface.NewColorEnum.NEW_RED;
        System.out.println(colorEnum);
    }
}

interface ColorInterface {
    enum ColorEnum implements ColorInterface {
        GREEN, YELLOW, RED
    }
    enum NewColorEnum implements ColorInterface {
        NEW_GREEN, NEW_YELLOW, NEW_RED
    }
}
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import java.util.ArrayList;
import java.util.EnumSet;
import java.util.List;

public class EnumTest {
    public static void main(String[] args) {
        List<ColorEnum> list = new ArrayList<ColorEnum>();
        list.add(ColorEnum.RED);
        list.add(ColorEnum.RED);  // 重复元素
        list.add(ColorEnum.YELLOW);
        list.add(ColorEnum.GREEN);
        // 去掉重复数据
        EnumSet<ColorEnum> enumSet = EnumSet.copyOf(list);
        System.out.println("去重：" + enumSet);

        // 获取指定范围的枚举（获取所有的失败状态）
        EnumSet<ErrorCodeEnum> errorCodeEnums = EnumSet.range(ErrorCodeEnum.ERROR, ErrorCodeEnum.UNKNOWN_ERROR);
        System.out.println("所有失败状态：" + errorCodeEnums);
    }
}

enum ColorEnum {
    RED("红色", 1), GREEN("绿色", 2), BLANK("白色", 3), YELLOW("黄色", 4);
    private String name;
    private int index;

    private ColorEnum(String name, int index) {
        this.name = name;
        this.index = index;
    }
}

enum ErrorCodeEnum {
    SUCCESS(1000, "success"),
    ERROR(2001, "parameter error"),
    SYS_ERROR(2002, "system error"),
    NAMESPACE_NOT_FOUND(2003, "namespace not found"),
    NODE_NOT_EXIST(3002, "node not exist"),
    NODE_ALREADY_EXIST(3003, "node already exist"),
    UNKNOWN_ERROR(9999, "unknown error");

    private int code;
    private String msg;

    ErrorCodeEnum(int code, String msg) {
        this.code = code;
        this.msg = msg;
    }

    public int code() {
        return code;
    }

    public String msg() {
        return msg;
    }
}
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import java.util.EnumMap;

public class EnumTest {
    public static void main(String[] args) {
        EnumMap<ColorEnum, String> enumMap = new EnumMap<>(ColorEnum.class);
        enumMap.put(ColorEnum.RED, "红色");
        enumMap.put(ColorEnum.GREEN, "绿色");
        enumMap.put(ColorEnum.BLANK, "白色");
        enumMap.put(ColorEnum.YELLOW, "黄色");
        System.out.println(ColorEnum.RED + ":" + enumMap.get(ColorEnum.RED));
    }
}

enum ColorEnum {
    RED, GREEN, BLANK, YELLOW;
}
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public static final int COLOR_RED = 1;
public static final int COLOR_BLUE = 2;
public static final int COLOR_GREEN = 3;
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public static final String COLOR_RED = "RED";
public static final String COLOR_BLUE = "BLUE";
public static final String COLOR_GREEN = "GREEN";
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public class EnumTest {
    public static final String COLOR_RED = "RED";
    public static final String COLOR_BLUE = "BLUE";
    public static final String COLOR_GREEN = "GREEN";
    public static void main(String[] args) {
        String color = "BLUE";
        if ("BLUE".equals(color)) {
            System.out.println("蓝色");
        }
    }
}
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public class Singleton {
    // 枚举类型是线程安全的，并且只会装载一次
    private enum SingletonEnum {
        INSTANCE;
        // 声明单例对象
        private final Singleton instance;
        // 实例化
        SingletonEnum() {
            instance = new Singleton();
        }
        private Singleton getInstance() {
            return instance;
        }
    }
    // 获取实例（单例对象）
    public static Singleton getInstance() {
        return SingletonEnum.INSTANCE.getInstance();
    }
    private Singleton() {
    }
    // 类方法
    public void sayHi() {
        System.out.println("Hi,Java.");
    }
}
class SingletonTest {
    public static void main(String[] args) {
        Singleton singleton = Singleton.getInstance();
        singleton.sayHi();
    }
}
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public enum ColorEnumTest {
    RED, GREEN, BLANK, YELLOW;
}
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public final class ColorEnumTest extends java.lang.Enum<ColorEnumTest> {
  public static final ColorEnumTest RED;
  public static final ColorEnumTest GREEN;
  public static final ColorEnumTest BLANK;
  public static final ColorEnumTest YELLOW;
  public static ColorEnumTest[] values();
  public static ColorEnumTest valueOf(java.lang.String);
  static {};
}
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public final boolean equals(Object other) {
    return this==other;
}
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