10、Java项目实战

本章将通过一个实战项目演示如何应用前面所学的Java知识，构建一个完整的个人记账本Web应用。

10.1 实战项目：个人记账本Web应用

10.1.1 项目概述

我们将构建一个简单的个人记账本Web应用，用户可以记录和查看他们的收入和支出。

10.1.2 技术栈

Spring Boot：用于快速构建和部署Web应用。
Spring Data JPA：用于数据持久化。
H2 Database：嵌入式数据库，用于快速开发和测试。
Thymeleaf：用于服务器端模板引擎，生成动态HTML页面。

10.2 项目架构设计与实现

10.2.1 创建项目结构

使用Spring Initializr创建一个新的Spring Boot项目，包含以下依赖：

Spring Web
Spring Data JPA
H2 Database
Thymeleaf

10.2.2 定义实体类

示例：定义交易记录实体类

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import java.time.LocalDate;

@Entity
public class Transaction {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String type; // "income" or "expense"
    private double amount;
    private String description;
    private LocalDate date;

    // Getters and setters
    // ... 省略getter和setter代码
}

10.2.3 创建JPA仓库接口

示例：创建交易记录仓库

import org.springframework.data.jpa.repository.JpaRepository;

public interface TransactionRepository extends JpaRepository<Transaction, Long> {
    // JPA会自动生成CRUD操作的方法
}

10.2.4 创建服务类

示例：创建交易记录服务

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;
import java.util.Optional;

@Service
public class TransactionService {
    private final TransactionRepository transactionRepository;

    @Autowired
    public TransactionService(TransactionRepository transactionRepository) {
        this.transactionRepository = transactionRepository;
    }

    public List<Transaction> getAllTransactions() {
        return transactionRepository.findAll();
    }

    public Optional<Transaction> getTransactionById(Long id) {
        return transactionRepository.findById(id);
    }

    public Transaction saveTransaction(Transaction transaction) {
        return transactionRepository.save(transaction);
    }

    public void deleteTransaction(Long id) {
        transactionRepository.deleteById(id);
    }
}

10.2.5 创建控制器类

示例：创建交易记录控制器

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@Controller
@RequestMapping("/transactions")
public class TransactionController {
    private final TransactionService transactionService;

    @Autowired
    public TransactionController(TransactionService transactionService) {
        this.transactionService = transactionService;
    }

    @GetMapping
    public String getAllTransactions(Model model) {
        List<Transaction> transactions = transactionService.getAllTransactions();
        model.addAttribute("transactions", transactions);
        return "transactions"; // 返回的视图名称
    }

    @GetMapping("/new")
    public String showNewTransactionForm(Model model) {
        model.addAttribute("transaction", new Transaction());
        return "new_transaction";
    }

    @PostMapping
    public String saveTransaction(@ModelAttribute("transaction") Transaction transaction) {
        transactionService.saveTransaction(transaction);
        return "redirect:/transactions";
    }

    @GetMapping("/delete/{id}")
    public String deleteTransaction(@PathVariable Long id) {
        transactionService.deleteTransaction(id);
        return "redirect:/transactions";
    }
}

10.2.6 创建视图模板

示例：创建显示交易记录的视图模板

transactions.html

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <title>Transaction List</title>
</head>
<body>
    <h1>All Transactions</h1>
    <table>
        <tr>
            <th>ID</th>
            <th>Type</th>
            <th>Amount</th>
            <th>Description</th>
            <th>Date</th>
            <th>Actions</th>
        </tr>
        <tr th:each="transaction : ${transactions}">
            <td th:text="${transaction.id}">1</td>
            <td th:text="${transaction.type}">income</td>
            <td th:text="${transaction.amount}">100.0</td>
            <td th:text="${transaction.description}">Salary</td>
            <td th:text="${transaction.date}">2024-05-24</td>
            <td>
                <a th:href="@{/transactions/delete/{id}(id=${transaction.id})}">Delete</a>
            </td>
        </tr>
    </table>
    <a href="/transactions/new">Add New Transaction</a>
</body>
</html>

示例：创建新增交易记录的视图模板

new_transaction.html

<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head>
    <title>New Transaction</title>
</head>
<body>
    <h1>New Transaction</h1>
    <form th:action="@{/transactions}" th:object="${transaction}" method="post">
        <label>Type:</label>
        <select th:field="*{type}">
            <option value="income">Income</option>
            <option value="expense">Expense</option>
        </select>
        <br>

        <label>Amount:</label>
        <input type="text" th:field="*{amount}" />
        <br>

        <label>Description:</label>
        <input type="text" th:field="*{description}" />
        <br>

        <label>Date:</label>
        <input type="date" th:field="*{date}" />
        <br>

        <button type="submit">Save</button>
    </form>
</body>
</html>

10.3 测试与部署

10.3.1 单元测试

使用JUnit和Spring Test来编写和运行单元测试，以确保代码的正确性。

示例：测试交易记录服务

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.boot.test.context.SpringBootTest;

import static org.junit.jupiter.api.Assertions.*;

@SpringBootTest
class TransactionServiceTest {
    @Autowired
    private TransactionService transactionService;

    @Test
    void testSaveTransaction() {
        Transaction transaction = new Transaction();
        transaction.setType("income");
        transaction.setAmount(100.0);
        transaction.setDescription("Test Income");
        transaction.setDate(LocalDate.now());

        Transaction savedTransaction = transactionService.saveTransaction(transaction);
        assertNotNull(savedTransaction);
        assertEquals("income", savedTransaction.getType());
    }
}

10.3.2 集成测试

集成测试用于测试完整系统的功能，确保各个部分协同工作。

10.3.3 部署应用

将应用打包为JAR文件或WAR文件，并部署到服务器（如Tomcat）或云平台（如AWS、Heroku）。

示例：打包和运行Spring Boot应用

# 打包应用
mvn clean package

# 运行JAR文件
java -jar target/myapp-0.0.1-SNAPSHOT.jar