JSP：使用jsp包含’out’（jspWriter）的委托来改变表达式的行为

比如，有一个类MyJSPWriter扩展了JspWriter并实现了所有的抽象方法..并且print(String )被修改为添加一些特殊的行为，因此所有表达式都是字符串将被区别对待（可能我可以使用这个对于某些特殊编码或类似的东西 – 这是一个简化的例子）：

 package com.myproject.base; import java.io.IOException; import javax.servlet.jsp.JspWriter; public class MyJSPWriter extends JspWriter{ JspWriter out = null; public MyJSPWriter(JspWriter out) { super(0, true); this.out = out; } @Override public String toString() { return out.toString(); } @Override public void clear() throws IOException { out.clear(); } @Override public void clearBuffer() throws IOException { out.clearBuffer(); } @Override public void close() throws IOException { out.close(); } @Override public void flush() throws IOException { out.flush(); } @Override public int getRemaining() { return out.getRemaining(); } @Override public void newLine() throws IOException { out.newLine(); } @Override public void print(boolean b) throws IOException { out.print(b); } @Override public void print(char c) throws IOException { out.print(c); } @Override public void print(int i) throws IOException { out.print(i); } @Override public void print(long l) throws IOException { out.print(l); } @Override public void print(float f) throws IOException { out.print(f); } @Override public void print(double d) throws IOException { out.print(d); } @Override public void print(char[] s) throws IOException { out.print(s); } @Override public void print(String s) throws IOException { out.print("Processed String: " + s); } @Override public void print(Object obj) throws IOException { out.print(obj); } @Override public void println() throws IOException { out.println(); } @Override public void println(boolean x) throws IOException { out.println(x); } @Override public void println(char x) throws IOException { out.println(x); } @Override public void println(int x) throws IOException { out.println(x); } @Override public void println(long x) throws IOException { out.println(x); } @Override public void println(float x) throws IOException { out.println(x); } @Override public void println(double x) throws IOException { out.println(x); } @Override public void println(char[] x) throws IOException { out.println(x); } @Override public void println(String x) throws IOException { out.println(x); } @Override public void println(Object x) throws IOException { out.println(x); } @Override public void write(char[] cbuf, int off, int len) throws IOException { out.write(cbuf, off, len); } } 

我有jsp（比如Main.jsp ）看起来像这样：

所以，在我的输出中，它会显示为

 Processed String: Hello World 

现在，如果我有更多的jsp：includes，并且可能在每个中包含更多内容…例如：

main.jsp中

Sub1.jsp

Sub2.jsp

等等…

但是所有的子jsp都会有他们自己的对象… 🙁

如何在不添加的情况下为所有包含的jsps带来相同的行为

在每个这些文件中（因为我试图在遗留应用程序中使用它）？

有没有其他方法我可以接近这个？

附加信息：当我们查看生成的jsp的.java文件时，这就是代码的一部分

 public void _jspService(HttpServletRequest request, HttpServletResponse response) throws java.io.IOException, ServletException { PageContext pageContext = null; HttpSession session = null; ServletContext application = null; ServletConfig config = null; JspWriter out = null; Object page = this; JspWriter _jspx_out = null; 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 = new MyJSPWriter(out); // and so on writing content .... 

Answer 1

如果查看生成的jsp类的顶部，您将看到以下行

  private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory(); 

现在，定制out对象的一种可能的解决方案是使用自定义JspFactory 。

脚步

创建自定义JspFactory实现

 public class MyJspFactory extends JspFactory { private static JspFactory _myFactory = null; public MyJspFactory(JspFactory factory) { _myFactory = factory; } //All abstract methods which looks up _myFactory and does the same thing public PageContext getPageContext(Servlet servlet, ServletRequest request, ServletResponse response, String errorPageURL, boolean needsSession, int bufferSize, boolean autoflush) { PageContext myCtxt = _myFactory.getPageContext(....) //Create a customPageContext and wrap myCtxt in it and return } } 

创建一个CutsomPageContext类

 public class MyPageContext extends PageContext { private PageContext _ctxt = null; public void setPageContext(PageContext ctxt) { _ctxt = ctxt; } //Implement all abstract methods using _ctxt object @override public JspWriter getOut() { JspWriter _out = _ctxt.getOut(); //Wrap _out object using MyJSPWriter as mentioned in question and return back; } } 

现在，在servlet的init面中，添加以下行

 JspFactory newFactory = new MyJspFactory(JspFactory.getDefaultFactory()); JspFactory.setDefaultFactory(newFactory); 

我还没试过。 但从概念上讲它应该有效。 如果您能通过此获得您想要的结果，请告诉我们。

祝好运！