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[BAEL-2842] SQL JOINS (#6718)

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This commit is contained in:
FrancoCorleone 2019-04-14 22:10:01 +02:00 committed by maibin
parent 14bf329f9f
commit 2cc1de2e39
4 changed files with 204 additions and 5 deletions
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18
persistence-modules/core-java-persistence/pom.xml
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@ -6,15 +6,21 @@
<version>0.1.0-SNAPSHOT</version>
<name>core-java-persistence</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung</groupId>
<artifactId>parent-java</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../../parent-java</relativePath>
</parent>
<dependencies>
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>${postgresql.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
@ -52,7 +58,7 @@
<version>${springframework.boot.spring-boot-starter.version}</version>
</dependency>
</dependencies>
<build>
<finalName>core-java-persistence</finalName>
<resources>
@ -62,8 +68,10 @@
</resource>
</resources>
</build>
<properties>
<postgresql.version>42.2.5.jre7</postgresql.version>
<mysql-connector.version>8.0.15</mysql-connector.version>
<assertj-core.version>3.10.0</assertj-core.version>
<h2database.version>1.4.197</h2database.version>
<commons-dbcp2.version>2.4.0</commons-dbcp2.version>
@ -72,5 +80,5 @@
<springframework.boot.spring-boot-starter.version>1.5.8.RELEASE</springframework.boot.spring-boot-starter.version>
<springframework.spring-web.version>4.3.4.RELEASE</springframework.spring-web.version>
</properties>
</project>

41
persistence-modules/core-java-persistence/src/main/java/com/baeldung/jdbc/joins/ArticleWithAuthor.java Normal file
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@ -0,0 +1,41 @@
package com.baeldung.jdbc.joins;
class ArticleWithAuthor {
private String title;
private String authorFirstName;
private String authorLastName;
public ArticleWithAuthor(String title, String authorFirstName, String authorLastName) {
this.title = title;
this.authorFirstName = authorFirstName;
this.authorLastName = authorLastName;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getAuthorFirstName() {
return authorFirstName;
}
public void setAuthorFirstName(String authorFirstName) {
this.authorFirstName = authorFirstName;
}
public String getAuthorLastName() {
return authorLastName;
}
public void setAuthorLastName(String authorLastName) {
this.authorLastName = authorLastName;
}
}

61
persistence-modules/core-java-persistence/src/main/java/com/baeldung/jdbc/joins/ArticleWithAuthorDAO.java Normal file
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@ -0,0 +1,61 @@
package com.baeldung.jdbc.joins;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
class ArticleWithAuthorDAO {
private static final String QUERY_TEMPLATE = "SELECT ARTICLE.TITLE, AUTHOR.LAST_NAME, AUTHOR.FIRST_NAME FROM ARTICLE %s AUTHOR ON AUTHOR.id=ARTICLE.AUTHOR_ID";
private final Connection connection;
ArticleWithAuthorDAO(Connection connection) {
this.connection = connection;
}
List<ArticleWithAuthor> articleInnerJoinAuthor() {
String query = String.format(QUERY_TEMPLATE, "INNER JOIN");
return executeQuery(query);
}
List<ArticleWithAuthor> articleLeftJoinAuthor() {
String query = String.format(QUERY_TEMPLATE, "LEFT JOIN");
return executeQuery(query);
}
List<ArticleWithAuthor> articleRightJoinAuthor() {
String query = String.format(QUERY_TEMPLATE, "RIGHT JOIN");
return executeQuery(query);
}
List<ArticleWithAuthor> articleFullJoinAuthor() {
String query = String.format(QUERY_TEMPLATE, "FULL JOIN");
return executeQuery(query);
}
private List<ArticleWithAuthor> executeQuery(String query) {
try (Statement statement = connection.createStatement()) {
ResultSet resultSet = statement.executeQuery(query);
return mapToList(resultSet);
} catch (SQLException e) {
e.printStackTrace();
}
return null;
}
private List<ArticleWithAuthor> mapToList(ResultSet resultSet) throws SQLException {
List<ArticleWithAuthor> list = new ArrayList<>();
while (resultSet.next()) {
ArticleWithAuthor articleWithAuthor = new ArticleWithAuthor(
resultSet.getString("TITLE"),
resultSet.getString("FIRST_NAME"),
resultSet.getString("LAST_NAME")
);
list.add(articleWithAuthor);
}
return list;
}
}

89
persistence-modules/core-java-persistence/src/test/java/com/baeldung/jdbc/joins/ArticleWithAuthorDAOIntegrationTest.java Normal file
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@ -0,0 +1,89 @@
package com.baeldung.jdbc.joins;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.List;
import static org.assertj.core.api.Assertions.assertThat;
public class ArticleWithAuthorDAOIntegrationTest {
private Connection connection;
private ArticleWithAuthorDAO articleWithAuthorDAO;
@Before
public void setup() throws ClassNotFoundException, SQLException {
Class.forName("org.postgresql.Driver");
connection = DriverManager.getConnection("jdbc:postgresql://localhost:5432/myDb", "user", "pass");
articleWithAuthorDAO = new ArticleWithAuthorDAO(connection);
Statement statement = connection.createStatement();
String createAuthorSql = "CREATE TABLE IF NOT EXISTS AUTHOR (ID int NOT NULL PRIMARY KEY, FIRST_NAME varchar(255), LAST_NAME varchar(255));";
String createArticleSql = "CREATE TABLE IF NOT EXISTS ARTICLE (ID int NOT NULL PRIMARY KEY, TITLE varchar(255) NOT NULL, AUTHOR_ID int, FOREIGN KEY(AUTHOR_ID) REFERENCES AUTHOR(ID));";
statement.execute(createAuthorSql);
statement.execute(createArticleSql);
insertTestData(statement);
}
@Test
public void whenQueryWithInnerJoin_thenShouldReturnProperRows() {
List<ArticleWithAuthor> articleWithAuthorList = articleWithAuthorDAO.articleInnerJoinAuthor();
assertThat(articleWithAuthorList).hasSize(4);
assertThat(articleWithAuthorList).noneMatch(row -> row.getAuthorFirstName() == null || row.getTitle() == null);
}
@Test
public void whenQueryWithLeftJoin_thenShouldReturnProperRows() {
List<ArticleWithAuthor> articleWithAuthorList = articleWithAuthorDAO.articleLeftJoinAuthor();
assertThat(articleWithAuthorList).hasSize(5);
assertThat(articleWithAuthorList).anyMatch(row -> row.getAuthorFirstName() == null);
}
@Test
public void whenQueryWithRightJoin_thenShouldReturnProperRows() {
List<ArticleWithAuthor> articleWithAuthorList = articleWithAuthorDAO.articleRightJoinAuthor();
assertThat(articleWithAuthorList).hasSize(5);
assertThat(articleWithAuthorList).anyMatch(row -> row.getTitle() == null);
}
@Test
public void whenQueryWithFullJoin_thenShouldReturnProperRows() {
List<ArticleWithAuthor> articleWithAuthorList = articleWithAuthorDAO.articleFullJoinAuthor();
assertThat(articleWithAuthorList).hasSize(6);
assertThat(articleWithAuthorList).anyMatch(row -> row.getTitle() == null);
assertThat(articleWithAuthorList).anyMatch(row -> row.getAuthorFirstName() == null);
}
@After
public void cleanup() throws SQLException {
connection.createStatement().execute("DROP TABLE ARTICLE");
connection.createStatement().execute("DROP TABLE AUTHOR");
connection.close();
}
public void insertTestData(Statement statement) throws SQLException {
String insertAuthors = "INSERT INTO AUTHOR VALUES "
+ "(1, 'Siena', 'Kerr'),"
+ "(2, 'Daniele', 'Ferguson'),"
+ "(3, 'Luciano', 'Wise'),"
+ "(4, 'Jonas', 'Lugo');";
String insertArticles = "INSERT INTO ARTICLE VALUES "
+ "(1, 'First steps in Java', 1),"
+ "(2, 'SpringBoot tutorial', 1),"
+ "(3, 'Java 12 insights', null),"
+ "(4, 'SQL JOINS', 2),"
+ "(5, 'Introduction to Spring Security', 3);";
statement.execute(insertAuthors);
statement.execute(insertArticles);
}
}