WEB API 실습1

oyeon·2021년 1월 22일
0
  1. pom.xml 수정
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>kr.or.connect</groupId>
	<artifactId>webapiexam</artifactId>
	<packaging>war</packaging>
	<version>0.0.1-SNAPSHOT</version>
	<name>webapiexam Maven Webapp</name>
	<url>http://maven.apache.org</url>
	<properties>
		<!-- web.xml 파일을 삭제해도 eclipse에서 오류가 발생하지 않는다. -->
		<failOnMissingWebXml>false</failOnMissingWebXml>
	</properties>
	<dependencies>
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>8.0.22</version>
		</dependency>
		
		<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-databind</artifactId>
			<version>2.9.4</version>
		</dependency>

		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>javax.servlet-api</artifactId>
			<version>3.1.0</version>
			<scope>provided</scope>
		</dependency>

		<dependency>
			<groupId>jstl</groupId>
			<artifactId>jstl</artifactId>
			<version>1.2</version>
		</dependency>

		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>3.8.1</version>
			<scope>test</scope>
		</dependency>
	</dependencies>
	<build>
		<finalName>webapiexam</finalName>
		<plugins>
			<plugin>
				<groupId>org.apache.maven.plugins</groupId>
				<artifactId>maven-compiler-plugin</artifactId>
				<version>3.6.1</version>
				<configuration>
					<source>1.8</source>
					<target>1.8</target>
				</configuration>
			</plugin>
		</plugins>
	</build>
</project>
  1. Role.java 추가 (DTO) - JDBC 실습 자료
package kr.or.connect.jdbcexam.dto;

public class Role {
	private Integer roleId;
	private String description;

	public Role() {

	}

	public Role(Integer roleId, String description) {
		super();
		this.roleId = roleId;
		this.description = description;
	}

	public Integer getRoleId() {
		return roleId;
	}

	public void setRoleId(Integer roleId) {
		this.roleId = roleId;
	}

	public String getDescription() {
		return description;
	}

	public void setDescription(String description) {
		this.description = description;
	}

	@Override
	public String toString() {
		return "Role [roleId=" + roleId + ", description=" + description + "]";
	}
}
  1. RoleDao.java 추가 (DAO) - JDBC 실습 자료
package kr.or.connect.jdbcexam.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import kr.or.connect.jdbcexam.dto.Role;

public class RoleDao {
	private static String dburl = "jdbc:mysql://localhost:3306/connectdb?serverTimezone=UTC";
	private static String dbUser = "connectuser";
	private static String dbpasswd = "PASSWORD";

	public List<Role> getRoles(){
		List<Role> list = new ArrayList<Role>(); 
		
		try {
			Class.forName("com.mysql.cj.jdbc.Driver");
		} catch(ClassNotFoundException e) {
			e.printStackTrace();
		}
		
		String sql = "SELECT description, role_id FROM role order by role_id desc";
		
		// try with resource - finally에서 close를 생략할 수 있는 방법
		try (Connection conn = DriverManager.getConnection(dburl, dbUser, dbpasswd);
				PreparedStatement ps = conn.prepareStatement(sql)){
			
			try(ResultSet rs = ps.executeQuery()){
	
				while (rs.next()) {
					String description = rs.getString(1);
					int id = rs.getInt("role_id");
					Role role = new Role(id, description);
					list.add(role);
				}
			} catch(Exception e) {
				e.printStackTrace();
			}			
		} catch (Exception e) {
			e.printStackTrace();
		}
		return list;
	}
}
  1. RolesServlet.java 생성
package kr.or.connect.webapiexam.api;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.fasterxml.jackson.databind.ObjectMapper;

import kr.or.connect.jdbcexam.dao.RoleDao;
import kr.or.connect.jdbcexam.dto.Role;

@WebServlet("/roles")
public class RolesServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;

	public RolesServlet() {
        super();
    }
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		response.setCharacterEncoding("utf-8");
		response.setContentType("application/json");

		RoleDao dao = new RoleDao();

		List<Role> list = dao.getRoles();

		/* jackson-databind 라이브러리가 제공하는 ObjectMapper 객체 사용
		 * 객체를 JSON 문자열로 바꾸거나, JSON 문자열을 객체로 바꾸는 역할 
		 */
		ObjectMapper objectMapper = new ObjectMapper();
		
		/* writeValueAsString 메서드는 list를 JSON 문자열로 바뀌게 해준다.
		 */
		String json = objectMapper.writeValueAsString(list);

		System.out.println(json);
		
		PrintWriter out = response.getWriter();
		out.println(json);
		out.close();
	}
}

결과

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