Thymeleaf條件判斷
本文章將介紹Thymeleaf標準表示式語法中的概念。我們將使用th:if和th:unless標記在模板中迭代顯示產品列表，如果產品的價格大於100，則會顯示:「特殊提供」。
編輯原始碼以便將產品列表顯示為表格行。已經將Product類的物件列表設定為具有變數名稱productList的上下文模型(參考:MyController.java中的實現)。
如果要上機實踐，請參考:Thymeleaf+SpringMVC5範例專案。這裡不再重複建立專案的過程，這裡將只介紹如何使用Thymeleaf標準表示式和標籤。
這裡建立一個Maven Web專案: thymeleaf-tutorials ，其目錄結構如下所示 -
資料存取類的實現:DAO.java -
package com.yiibai.dao;
import java.math.BigDecimal;
import java.sql.Timestamp;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import com.yiibai.spring.bean.*;
/**
* Mock persistence.
*/
public class DAO {
private static final String NO_WEBSITE = null;
public static Product loadProduct() {
try {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
return new Product("Wooden wardrobe with glass doors", Integer.valueOf(850), sdf.parse("2013-02-18"));
} catch (ParseException ex) {
throw new RuntimeException("Invalid date");
}
}
public static List<Product> loadAllProducts() {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
List<Product> products = new ArrayList<Product>();
try {
products.add(new Product("花生油", Integer.valueOf(125), sdf.parse("2018-02-18")));
products.add(new Product("蘇打餅乾", Integer.valueOf(15), sdf.parse("208-02-15")));
products.add(new Product("拿鐵", Integer.valueOf(45), sdf.parse("2019-02-20")));
products.add(new Product("調和油", Integer.valueOf(20), sdf.parse("2019-02-21")));
products.add(new Product("大豆油", Integer.valueOf(49), sdf.parse("2019-02-15")));
products.add(new Product("玉米汁", Integer.valueOf(80), sdf.parse("2019-02-17")));
} catch (ParseException ex) {
throw new RuntimeException("Invalid date");
}
return products;
}
public static Timestamp loadReleaseDate() {
try {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm");
Date date = sdf.parse("2014-01-31 15:00");
return new Timestamp(date.getTime());
} catch (ParseException ex) {
throw new RuntimeException("Invalid date");
}
}
}
控制器類的實現:MyController.java -
package com.yiibai.spring.controller;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import com.yiibai.dao.DAO;
import com.yiibai.spring.bean.Product;
@Controller
public class MyController {
@GetMapping("/")
public String index(Model model) throws ParseException {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Product product = new Product("花生油", 129, sdf.parse("2018-02-18"));
model.addAttribute("product", product);
return "index";
}
@GetMapping("/escape")
public String escape(Model model) throws ParseException {
String html = "Welcome to our <b>fantastic</b> grocery store!";
model.addAttribute("html", html);
return "escape";
}
@GetMapping("/iteration")
public String iteration(Model model) throws ParseException {
List productList = DAO.loadAllProducts();
model.addAttribute("productList", productList);
return "iteration";
}
@GetMapping("/conditional")
public String conditional(Model model) throws ParseException {
List productList = DAO.loadAllProducts();
model.addAttribute("productList", productList);
return "conditional";
}
}
模板檔案的實現:/webapp/WEB-INFO/views/conditional.html -
<html xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<link rel="stylesheet" th:href="@{/css/main.css}" />
<style>
span.offer {
font-weight: bold;
color: green;
}
</style>
<title>SpringMVC5+Thymeleaf條件範例</title>
</head>
<body>
<h2>Spring MVC5 + Thymeleaf條件範例</h2>
<table>
<thead>
<tr>
<th>行序號</th>
<th>產品名稱</th>
<th>價格</th>
<th>有效日期</th>
<th>備註</th>
</tr>
</thead>
<tbody th:remove="all-but-first">
<tr th:each="product : ${productList}">
<td th:text="${productStat.count}">1</td>
<td th:text="${product.description}">Red chair</td>
<td th:text="${'￥' + #numbers.formatDecimal(product.price, 1, 2)}">￥350</td>
<td th:text="${#dates.format(product.availableFrom, 'dd-MM-yyyy')}">2018-02-20</td>
<td><span th:if="${product.price gt 100}" class="offer">特殊提供</span></td>
</tr>
<tr>
<td>White table</td>
<td>￥200</td>
<td>2018-04-10</td>
<td> </td>
</tr>
<tr>
<td>Reb table</td>
<td>￥200</td>
<td>2018-02-20</td>
<td> </td>
</tr>
<tr>
<td>Blue table</td>
<td>￥200</td>
<td>2018-02-20</td>
<td> </td>
</tr>
</tbody>
</table>
</body>
</html>
執行上面專案，在瀏覽器中顯示效果如下 -
高階應用
在這部分中，我們將演示其它幾個標籤(如:th:switch，th:case和th:unless)的用法。
需要重寫以下幾個檔案，DAO.java -
package com.yiibai.dao;
import java.math.BigDecimal;
import java.sql.Timestamp;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import com.yiibai.spring.bean.*;
/**
* Mock persistence.
*/
public class DAO {
private static final String NO_WEBSITE = null;
public static Product loadProduct() {
try {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
return new Product("Wooden wardrobe with glass doors", Integer.valueOf(850), sdf.parse("2013-02-18"), "");
} catch (ParseException ex) {
throw new RuntimeException("Invalid date");
}
}
public static List<Product> loadAllProducts() {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
List<Product> products = new ArrayList<Product>();
try {
products.add(new Product("花生油", Integer.valueOf(125), sdf.parse("2018-02-18"),"CG"));
products.add(new Product("蘇打餅乾", Integer.valueOf(15), sdf.parse("208-02-15"),"CG"));
products.add(new Product("拿鐵", Integer.valueOf(45), sdf.parse("2019-02-20"),"PT"));
products.add(new Product("調和油", Integer.valueOf(20), sdf.parse("2019-02-21"),"CX"));
products.add(new Product("大豆油", Integer.valueOf(49), sdf.parse("2019-02-15"),""));
products.add(new Product("玉米汁", Integer.valueOf(80), sdf.parse("2019-02-17"),""));
} catch (ParseException ex) {
throw new RuntimeException("Invalid date");
}
return products;
}
public static Timestamp loadReleaseDate() {
try {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm");
Date date = sdf.parse("2014-01-31 15:00");
return new Timestamp(date.getTime());
} catch (ParseException ex) {
throw new RuntimeException("Invalid date");
}
}
}
產品類的實現:Product.java -
package com.yiibai.spring.bean;
import java.util.Date;
public class Product {
private String description;
private Integer price;
private Date availableFrom;
private String saleType;// 銷售型別:促銷，拼團，閃購，其它
public String getSaleType() {
return saleType;
}
public void setSaleType(String saleType) {
this.saleType = saleType;
}
public Product(final String description, final Integer price, final Date availableFrom, final String saleType) {
this.description = description;
this.price = price;
this.availableFrom = availableFrom;
this.saleType = saleType;
}
public Date getAvailableFrom() {
return this.availableFrom;
}
public void setAvailableFrom(final Date availableFrom) {
this.availableFrom = availableFrom;
}
public String getDescription() {
return this.description;
}
public void setDescription(final String description) {
this.description = description;
}
public Integer getPrice() {
return this.price;
}
public void setPrice(final Integer price) {
this.price = price;
}
}
控制器類的實現:MyController.java -
package com.yiibai.spring.controller;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import com.yiibai.dao.DAO;
import com.yiibai.spring.bean.Product;
@Controller
public class MyController {
@GetMapping("/")
public String index(Model model) throws ParseException {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Product product = new Product("花生油", 129, sdf.parse("2018-02-18"), "");
model.addAttribute("product", product);
return "index";
}
@GetMapping("/escape")
public String escape(Model model) throws ParseException {
String html = "Welcome to our <b>fantastic</b> grocery store!";
model.addAttribute("html", html);
return "escape";
}
@GetMapping("/iteration")
public String iteration(Model model) throws ParseException {
List productList = DAO.loadAllProducts();
model.addAttribute("productList", productList);
return "iteration";
}
@GetMapping("/conditional")
public String conditional(Model model) throws ParseException {
List productList = DAO.loadAllProducts();
model.addAttribute("productList", productList);
return "conditional";
}
}
模板檔案的實現:/webapp/WEB-INFO/views/conditional.html -
<html xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<link rel="stylesheet" th:href="@{/css/main.css}" />
<style>
span.offer {
font-weight: bold;
color: green;
}
</style>
<title>SpringMVC5+Thymeleaf條件範例</title>
</head>
<body>
<h2>Spring MVC5 + Thymeleaf條件範例</h2>
<table>
<thead>
<tr>
<th>行序號</th>
<th>產品名稱</th>
<th>價格</th>
<th>有效日期</th>
<th>銷售型別</th>
<th>備註</th>
</tr>
</thead>
<tbody th:remove="all-but-first">
<tr th:each="product : ${productList}">
<td th:text="${productStat.count}">1</td>
<td th:text="${product.description}">Red chair</td>
<td th:text="${'￥' + #numbers.formatDecimal(product.price, 1, 2)}">￥350</td>
<td th:text="${#dates.format(product.availableFrom, 'dd-MM-yyyy')}">2018-02-20</td>
<td th:switch="${product.saleType}">
<span th:case="'CG'">閃購</span>
<span th:case="'PT'">拼團</span>
<span th:case="'CX'">促銷</span>
<span th:case="*">其它</span>
</td>
<td><span th:class="${product.price gt 100}?'offer'" th:text="${product.price}">特殊提供</span></td>
</tr>
<tr>
<td>White table</td>
<td>￥200</td>
<td>2018-04-10</td>
<td> </td>
</tr>
<tr>
<td>Reb table</td>
<td>￥200</td>
<td>2018-02-20</td>
<td> </td>
</tr>
<tr>
<td>Blue table</td>
<td>￥200</td>
<td>2018-02-20</td>
<td> </td>
</tr>
</tbody>
</table>
</body>
</html>
執行上面範例程式碼，得到以下結果 -