070_JSP詳解

目錄

• 什麼是JSP
• JSP原理
  • JSP源碼分析
  • JSP流程圖
  • JSP頁面轉java代碼
• JSP基礎文法
  • 示例
    • 建立maven-archetype-webapp項目
    • 替換web.xml為最新版本
    • 查詢https://mvnrepository.com，添加依賴到pom.xml
    • 配置Tomcat
  • • JSP表達式
    • JSP腳本
      • JSP檔案生成的java檔案
    • JSP聲明
    • 差別：JSP聲明會被編譯到JSP生成的java類中，JSP表達式和JSP聲明則會被編譯到JSP生成的_jspService方法中
• JSP指令
  • page 定義網頁屬性
  • include 包含其他頁面
  • taglib 引入标簽庫
• 9大内置對象
• JSP标簽、JSTL标簽、EL表達式
  • 需要依賴的包
  • JSP标簽
  • JSTL标簽
    • 安裝使用步驟
    • 核心标簽
    • 格式化标簽
    • SQL 标簽
    • XML 标簽
    • JSTL 函數
  • EL表達式
    • 擷取資料
    • 執行運算
    • 擷取web開發的常用對象
• JavaBean-實體類
  • JavaBean有特定的寫法
  • ORM-對象關系映射

Java Server Pages Java伺服器端頁面，和Servlet一樣，用于動态Web技術

特點：寫JSP，就像寫HTML一樣

與HTML的差別：

• HTML隻能給使用者提供靜态的資料
• JSP頁面中可以嵌入Java代碼，為使用者提供動态資料

1. Tomcat中有一個work目錄

1. IDEA中使用Tomcat會在IDEA的Tomcat中産生一個work目錄

1. jsp檔案會轉為java程式
2. 浏覽器向伺服器發送請求，不管通路什麼資源，其實都是在通路Servlet

/*
 * Generated by the Jasper component of Apache Tomcat
 * Version: Apache Tomcat/9.0.43
 * Generated at: 2021-03-16 15:12:15 UTC
 * Note: The last modified time of this file was set to
 *       the last modified time of the source file after
 *       generation to assist with modification tracking.
 */
package org.apache.jsp;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;

public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase
    implements org.apache.jasper.runtime.JspSourceDependent,
                 org.apache.jasper.runtime.JspSourceImports {

  private static final javax.servlet.jsp.JspFactory _jspxFactory =
          javax.servlet.jsp.JspFactory.getDefaultFactory();

  private static java.util.Map<java.lang.String,java.lang.Long> _jspx_dependants;

  private static final java.util.Set<java.lang.String> _jspx_imports_packages;

  private static final java.util.Set<java.lang.String> _jspx_imports_classes;

  static {
    _jspx_imports_packages = new java.util.HashSet<>();
    _jspx_imports_packages.add("javax.servlet");
    _jspx_imports_packages.add("javax.servlet.http");
    _jspx_imports_packages.add("javax.servlet.jsp");
    _jspx_imports_classes = null;
  }

  private volatile javax.el.ExpressionFactory _el_expressionfactory;
  private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager;

  public java.util.Map<java.lang.String,java.lang.Long> getDependants() {
    return _jspx_dependants;
  }

  public java.util.Set<java.lang.String> getPackageImports() {
    return _jspx_imports_packages;
  }

  public java.util.Set<java.lang.String> getClassImports() {
    return _jspx_imports_classes;
  }

  public javax.el.ExpressionFactory _jsp_getExpressionFactory() {
    if (_el_expressionfactory == null) {
      synchronized (this) {
        if (_el_expressionfactory == null) {
          _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
        }
      }
    }
    return _el_expressionfactory;
  }

  public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() {
    if (_jsp_instancemanager == null) {
      synchronized (this) {
        if (_jsp_instancemanager == null) {
          _jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
        }
      }
    }
    return _jsp_instancemanager;
  }

  public void _jspInit() {
  }

  public void _jspDestroy() {
  }

  public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
      throws java.io.IOException, javax.servlet.ServletException {

    if (!javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {
      final java.lang.String _jspx_method = request.getMethod();
      if ("OPTIONS".equals(_jspx_method)) {
        response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
        return;
      }
      if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method)) {
        response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
        response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSP 隻允許 GET、POST 或 HEAD。Jasper 還允許 OPTIONS");
        return;
      }
    }

    final javax.servlet.jsp.PageContext pageContext;
    javax.servlet.http.HttpSession session = null;
    final javax.servlet.ServletContext application;
    final javax.servlet.ServletConfig config;
    javax.servlet.jsp.JspWriter out = null;
    final java.lang.Object page = this;
    javax.servlet.jsp.JspWriter _jspx_out = null;
    javax.servlet.jsp.PageContext _jspx_page_context = null;


    try {
      response.setContentType("text/html");
      pageContext = _jspxFactory.getPageContext(this, request, response,
      			null, true, 8192, true);
      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();
      config = pageContext.getServletConfig();
      session = pageContext.getSession();
      out = pageContext.getOut();
      _jspx_out = out;

      out.write("<html>\n");
      out.write("<body>\n");
      out.write("<h2>Hello World!</h2>\n");
      out.write("</body>\n");
      out.write("</html>\n");
    } catch (java.lang.Throwable t) {
      if (!(t instanceof javax.servlet.jsp.SkipPageException)){
        out = _jspx_out;
        if (out != null && out.getBufferSize() != 0)
          try {
            if (response.isCommitted()) {
              out.flush();
            } else {
              out.clearBuffer();
            }
          } catch (java.io.IOException e) {}
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
        else throw new ServletException(t);
      }
    } finally {
      _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
}

           

// 初始化  
public void _jspInit() {
  }
// 銷毀
public void _jspDestroy() {
}
//JSPService
  public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
      throws java.io.IOException, javax.servlet.ServletException {
// 1.判斷請求
    if (!javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {
      final java.lang.String _jspx_method = request.getMethod();
      if ("OPTIONS".equals(_jspx_method)) {
        response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
        return;
      }
      if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method)) {
        response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
        response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSP 隻允許 GET、POST 或 HEAD。Jasper 還允許 OPTIONS");
        return;
      }
    }
// 2.内置對象
    final javax.servlet.jsp.PageContext pageContext;// 頁面上下文
    javax.servlet.http.HttpSession session = null;// 會話
    final javax.servlet.ServletContext application;// Servlet上下文
    final javax.servlet.ServletConfig config;// config
    javax.servlet.jsp.JspWriter out = null;// out
    final java.lang.Object page = this;// page目前頁面
    javax.servlet.jsp.JspWriter _jspx_out = null;
    javax.servlet.jsp.PageContext _jspx_page_context = null;


    try {
// 3.輸出頁面前增加的代碼，以下的對象可以在jsp頁面中直接使用
      response.setContentType("text/html");// 設定響應的頁面類型
      pageContext = _jspxFactory.getPageContext(this, request, response,
      			null, true, 8192, true);
      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();
      config = pageContext.getServletConfig();
      session = pageContext.getSession();
      out = pageContext.getOut();
      _jspx_out = out;
// 4.輸出頁面
      out.write("<html>\n");
      out.write("<body>\n");
      out.write("<h2>Hello World!</h2>\n");
      out.write("</body>\n");
      out.write("</html>\n");
    } catch (java.lang.Throwable t) {
      if (!(t instanceof javax.servlet.jsp.SkipPageException)){
        out = _jspx_out;
        if (out != null && out.getBufferSize() != 0)
          try {
            if (response.isCommitted()) {
              out.flush();
            } else {
              out.clearBuffer();
            }
          } catch (java.io.IOException e) {}
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
        else throw new ServletException(t);
      }
    } finally {
      _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
           

1. 頁面中的java代碼，會直接應用到java代碼中
2. 頁面中的HTML代碼，會轉換為

   out.write("<html>");

    ，輸出到頁面

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                      http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0"
         metadata-complete="true">

</web-app>
           

<?xml version="1.0" encoding="UTF-8"?>

<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/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.qing</groupId>
  <artifactId>javaweb-jsp</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <dependencies>
      <!--Servlet依賴-->
      <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
      <dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>javax.servlet-api</artifactId>
          <version>4.0.1</version>
      </dependency>
      <!--JSP依賴-->
      <!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
      <dependency>
          <groupId>javax.servlet.jsp</groupId>
          <artifactId>javax.servlet.jsp-api</artifactId>
          <version>2.3.3</version>
      </dependency>
      <!--JSTL表達式依賴-->
      <!-- https://mvnrepository.com/artifact/javax.servlet.jsp.jstl/jstl-api -->
      <dependency>
          <groupId>javax.servlet.jsp.jstl</groupId>
          <artifactId>jstl-api</artifactId>
          <version>1.2</version>
      </dependency>
      <!--standard标簽庫-->
      <!-- https://mvnrepository.com/artifact/taglibs/standard -->
      <dependency>
          <groupId>taglibs</groupId>
          <artifactId>standard</artifactId>
          <version>1.1.2</version>
      </dependency>
  </dependencies>
</project>

           

JSP作為java技術的一種應用，它擁有一些自己擴充的文法，java所有文法都支援。

<%--JSP表達式
作用：用來将程式的輸出，輸出到用戶端
文法：<%= 變量或者表達式 %>
--%>
<%=new java.util.Date()%>
<hr>
<%=2*3%>
           

<%--JSP腳本
作用：用來寫java方法内代碼
文法：<% java方法類代碼 %>          
--%>
<%
    int sum = 0;
    for (int i = 1; i <= 100; i++) {
        sum += i;
    }
    out.println("<h1>sum=" + sum + "</h1>");
%>
           

<%--在代碼中嵌入HTML--%>
<%
    for (int i = 0; i < 5; i++) {
%>
<h1>hello,world <%=i%></h1>
<%
    }
%>
           

public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
      throws java.io.IOException, javax.servlet.ServletException {

    if (!javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {
      final java.lang.String _jspx_method = request.getMethod();
      if ("OPTIONS".equals(_jspx_method)) {
        response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
        return;
      }
      if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method)) {
        response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
        response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSP 隻允許 GET、POST 或 HEAD。Jasper 還允許 OPTIONS");
        return;
      }
    }

    final javax.servlet.jsp.PageContext pageContext;
    javax.servlet.http.HttpSession session = null;
    final javax.servlet.ServletContext application;
    final javax.servlet.ServletConfig config;
    javax.servlet.jsp.JspWriter out = null;
    final java.lang.Object page = this;
    javax.servlet.jsp.JspWriter _jspx_out = null;
    javax.servlet.jsp.PageContext _jspx_page_context = null;


    try {
      response.setContentType("text/html");
      pageContext = _jspxFactory.getPageContext(this, request, response,
      			null, true, 8192, true);
      _jspx_page_context = pageContext;
      application = pageContext.getServletContext();
      config = pageContext.getServletConfig();
      session = pageContext.getSession();
      out = pageContext.getOut();
      _jspx_out = out;

      out.write("<html>\n");
      out.write("<body>\n");
      out.write('\n');
      out.print(new java.util.Date());
      out.write("\n");
      out.write("<hr>\n");
      out.print(2*3);
      out.write("\n");
      out.write("<hr>\n");
      out.write('\n');

    int sum = 0;
    for (int i = 1; i <= 100; i++) {
        sum += i;
    }
    out.println("<h1>sum=" + sum + "</h1>");

      out.write('\n');
      out.write('\n');

    for (int i = 0; i < 5; i++) {

      out.write("\n");
      out.write("<h1>hello,world ");
      out.print(i);
      out.write("</h1>\n");

    }

      out.write("\n");
      out.write("</body>\n");
      out.write("</html>\n");
    } catch (java.lang.Throwable t) {
      if (!(t instanceof javax.servlet.jsp.SkipPageException)){
        out = _jspx_out;
        if (out != null && out.getBufferSize() != 0)
          try {
            if (response.isCommitted()) {
              out.flush();
            } else {
              out.clearBuffer();
            }
          } catch (java.io.IOException e) {}
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
        else throw new ServletException(t);
      }
    } finally {
      _jspxFactory.releasePageContext(_jspx_page_context);
    }
  }
           

<%--JSP聲明
作用：用來寫java類内代碼
文法：<%! java類内代碼 %>          
--%>
<%!
    static {
        System.out.println("靜态代碼塊");
    }
    private int globalVal = 0;
    public void test() {
        System.out.println(globalVal);
    }
%>
           

生成的java代碼

static {
        System.out.println("靜态代碼塊");
    }
private int globalVal = 0;
public void test() {
    System.out.println(globalVal);
}
           

<%--導包--%>
<%@ page import="java.util.Date" %>
           

<%--定制錯誤頁面，錯誤時跳轉到自定義錯誤頁面--%>
<%@ page errorPage="error/500.jsp" %>
           

<%--顯式聲明這是一個錯誤頁面--%>
<%@ page isErrorPage="true" %>
           

<%--定義頁面編碼--%>
<%@ page pageEncoding="utf-8" %>
           

<%--jsp指令--%>
<%--引入公用頭部--%>
<%@ include file="common/header.jsp"%>
<h1>網頁主體</h1>
<%--引入公用底部--%>
<%@ include file="common/footer.jsp"%>

<%--兩者的差別：
jsp指令，會将兩個頁面合并到本頁面
jsp标簽，拼接頁面，本質還是三個頁面
jsp标簽比較常用，注：jsp标簽路徑加/，代表web根目錄
--%>

<%--jsp标簽--%>
<%--引入公用頭部--%>
<jsp:include page="/common/header.jsp"/>
<h1>網頁主體</h1>
<%--引入公用底部--%>
<jsp:include page="/common/footer.jsp"/>
           

1. javax.servlet.http.HttpServletRequest request
2. javax.servlet.http.HttpServletResponse response
3. javax.servlet.ServletException exception
4. javax.servlet.jsp.PageContext pageContext
5. javax.servlet.http.HttpSession session
6. javax.servlet.ServletContext application
7. javax.servlet.ServletConfig config
8. javax.servlet.jsp.JspWriter out
9. java.lang.Object page = this

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

<%--内置對象--%>
<%
    pageContext.setAttribute("name1", "1号");// 儲存的資料在一個頁面有效
    request.setAttribute("name2", "2号");// 儲存的資料在一個請求有效，請求轉發會攜帶這個資料
    session.setAttribute("name3", "3号");// 儲存的資料在一個回話有效，從打開浏覽器到關閉浏覽器
    application.setAttribute("name4", "4号");// 儲存的資料在伺服器中有效，從啟動伺服器到關閉伺服器
%>

<%--腳本片段中的代碼會原封不動的生成到jsp.java，是以jsp腳本中的代碼遵守java文法，注釋也用java注釋--%>
<%
    // 從pageContext中取值，通過尋找的方式來，從底層到高層（作用域）：pageContext<request<session<application
    String name1 = (String) pageContext.findAttribute("name1");
    String name2 = (String) pageContext.findAttribute("name2");
    String name3 = (String) pageContext.findAttribute("name3");
    String name4 = (String) pageContext.findAttribute("name4");
    String name5 = (String) pageContext.findAttribute("name5");
%>

<%--使用JSP表達式和EL表達式輸出的差別：針對沒有的資料，JSP表達式會輸出null，EL表達式不會輸出--%>
<h1>JSP表達式輸出值</h1>
<h3><%=name1%></h3>
<h3><%=name2%></h3>
<h3><%=name3%></h3>
<h3><%=name4%></h3>
<h3><%=name5%></h3>

<hr>

<h1>EL表達式輸出值</h1>
<h3>${name1}</h3>
<h3>${name2}</h3>
<h3>${name3}</h3>
<h3>${name4}</h3>
<h3>${name5}</h3>

</body>
</html>
           

<!--JSTL表達式依賴-->
      <!-- https://mvnrepository.com/artifact/javax.servlet.jsp.jstl/jstl-api -->
      <dependency>
          <groupId>javax.servlet.jsp.jstl</groupId>
          <artifactId>jstl-api</artifactId>
          <version>1.2</version>
      </dependency>
      <!--standard标簽庫-->
      <!-- https://mvnrepository.com/artifact/taglibs/standard -->
      <dependency>
          <groupId>taglibs</groupId>
          <artifactId>standard</artifactId>
          <version>1.1.2</version>
      </dependency>
           

<%--包含頁面--%>
<jsp:include page="header.jsp"></jsp:include>

<%--請求轉發--%>
<jsp:forward page="500.jsp">
    <jsp:param name="id" value="1"></jsp:param>
    <jsp:param name="name" value="張三豐"></jsp:param>
</jsp:forward>
           

https://www.runoob.com/jsp/jsp-jstl.html

JSTL标簽庫的使用是為了彌補HTML标簽的不足，它自定義了許多标簽，可以供我們使用，标簽的功能和java代碼一樣。

1. Tomcat安裝JSTL标簽庫

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" 
    xmlns="http://java.sun.com/xml/ns/j2ee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
        http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    <jsp-config>
    <taglib>
    <taglib-uri>http://java.sun.com/jsp/jstl/fmt</taglib-uri>
    <taglib-location>/WEB-INF/fmt.tld</taglib-location>
    </taglib>
    <taglib>
    <taglib-uri>http://java.sun.com/jsp/jstl/fmt-rt</taglib-uri>
    <taglib-location>/WEB-INF/fmt-rt.tld</taglib-location>
    </taglib>
    <taglib>
    <taglib-uri>http://java.sun.com/jsp/jstl/core</taglib-uri>
    <taglib-location>/WEB-INF/c.tld</taglib-location>
    </taglib>
    <taglib>
    <taglib-uri>http://java.sun.com/jsp/jstl/core-rt</taglib-uri>
    <taglib-location>/WEB-INF/c-rt.tld</taglib-location>
    </taglib>
    <taglib>
    <taglib-uri>http://java.sun.com/jsp/jstl/sql</taglib-uri>
    <taglib-location>/WEB-INF/sql.tld</taglib-location>
    </taglib>
    <taglib>
    <taglib-uri>http://java.sun.com/jsp/jstl/sql-rt</taglib-uri>
    <taglib-location>/WEB-INF/sql-rt.tld</taglib-location>
    </taglib>
    <taglib>
    <taglib-uri>http://java.sun.com/jsp/jstl/x</taglib-uri>
    <taglib-location>/WEB-INF/x.tld</taglib-location>
    </taglib>
    <taglib>
    <taglib-uri>http://java.sun.com/jsp/jstl/x-rt</taglib-uri>
    <taglib-location>/WEB-INF/x-rt.tld</taglib-location>
    </taglib>
    </jsp-config>
</web-app>
           

1. 使用任何庫，必須在每個 JSP 檔案中的頭部包含  标簽。

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
           

<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
           

<%@ taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql" %>
           

<%@ taglib prefix="x" uri="http://java.sun.com/jsp/jstl/xml" %>
           

<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
           

1. 必須有一個無參構造，如果沒有有參構造，無參構造隐式預設有
2. 屬性必須私有化private
3. 必須有對應的get/set方法

一般用來和資料庫的字段做映射

• 表-->類
• 字段-->屬性
• 行記錄-->對象